MnO2 Electrocatalysts Coordinating Alcohol Oxidation for Ultra-Durable Hydrogen and Chemical Productions in Acidic Solutions

Article abstract of DOI:10.1002/anie.202107510

Electrocatalytic hydrogen production under acidic conditions is of great importance for industrialization in comparison to that in alkaline media, which, unfortunately, still remains challenging due to the lack of earth-abundant, cost-effective and highly active anodic electrocatalysts that can be used durably under strongly acidic conditions. Here we report an unexpected finding that manganese oxide, a kind of common non-noble catalysts easily soluble in acidic solutions, can be applied as a highly efficient and extremely durable anodic electrocatalyst for hydrogen production from an acidic aqueous solution of alcohols. Particularly in a glycerol solution, a potential of as low as 1.36 V (vs. RHE) is needed at 10 mA cm^?2, which is 270 mV lower than that of oxygen evolution reaction (OER), to oxidize glycerol into value-added chemicals such as formic acid, without oxygen production. To our surprise, the manganese oxide exhibits extremely high stability for electrocatalytic hydrogen production in coupling with glycerol oxidation for longer than 865 hours compared to shorter than 10 h for OER. Moreover, the effect of the addition of glycerol on the electrochemical durability has been probed via in situ Raman spectroscopic analysis and density functional theory (DFT) calculations. This work demonstrates that acid-unstable metal oxide electrocatalysts can be used robustly in acidic media under the presence of certain substances for electrochemical purposes, such as hydrogen production.

Full text of DOI:10.1002/anie.202107510

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
www.angewandte.org
Accepted Article
Title: MnO2 Electrocatalysts Coordinating Alcohol Oxidation for Ultra-
durable Hydrogen and Chemical Productions in Acidic Solutions
Authors: Yan Li, Xinfa Wei, Shuhe Han, Lisong Chen, and Jianlin Shi
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.202107510
Link to VoR: https://doi.org/10.1002/anie.202107510

10.1002/anie.202107510
Angewandte Chemie International Edition
RESEARCH ARTICLE
MnO2 Electrocatalysts Coordinating Alcohol Oxidation for Ultra-
durable Hydrogen and Chemical Productions in Acidic Solutions
Yan Li,[a] Xinfa Wei,[a] Shuhe Han,[c] Lisong Chen,*[a] Jianlin Shi*[b]
[a]
[b]
[c]
Y. Li, Dr. X. Wei, prof. L. Chen
Shanghai Key Laboratory of Green Chemistry and Chemical Processes
School of Chemistry and Molecular Engineering, East China Normal University
Shanghai 200062, P. R. China
E-mail: lschen@chem.ecnu.edu.cn
Prof. J. Shi
State Key Laboratory of High Performance Ceramics and Superfine Microstructures
Shanghai Institute of Ceramics, Chinese Academy of Sciences
Shanghai 200050, P. R. China
E-mail: jlshi@mail.sic.ac.cn
S. H
Department of Chemistry, Institute of Molecular Plus
School of Science, Tianjin University
Tianjin 300072 (China)
Supporting information for this article is given via a link at the end of the document.
Abstract: Electrocatalytic hydrogen production under acidic
conditions is of great importance for industrialization in comparison to
that in alkaline media, which, unfortunately, still remains great
challenges due to the lack of earth-abundant, cost-effective and highly
active anodic electrocatalysts that can be used durably under strongly
acidic conditions. Here we report an unexpected finding that
manganese oxide, a kind of common non-noble catalysts easily
soluble in acidic solutions, can be applied as a highly efficient and
extremely durable anodic electrocatalyst for hydrogen production
from an acidic aqueous solution of alcohols. Particularly in a glycerol
solution, a potential of as low as 1.36 V (vs. RHE) is needed at 10 mA
cm-2, which is 270 mV lower than that of oxygen evolution reaction
(OER), to oxidize glycerol into value-added chemicals such as formic
acid, without oxygen production. To our surprise, the manganese
oxide exhibits extremely high stability for electrocatalytic hydrogen
production in coupling with glycerol oxidation for longer than 865
hours compared to shorter than 10 h for OER. Moreover, the effect of
the addition of glycerol on the electrochemical durability has been
probed via in situ Raman spectroscopic analysis and density
functional theory (DFT) calculation. This work opens an
unprecedented window that acidity-unstable metal oxide
electrocatalysts can be used robustly in acidic media under the
presence of certain substances for electrochemical purposes, such as
hydrogen production.
for cathodic HER have been designed for uses in a wide pH range.
However, the development of catalysts for anodic OER, which
serves as the electron donor for cathodic hydrogen evolution, still
remains a great challenge because a high overpotential is
necessary for overcoming energy barrier of OER.[2] Especially,
though vitally important for coupling with cathodic HER in the
presence of elevated concentrations of proton owing to the much
faster kinetics, anodic catalysts in acidic electrolyte have been
seldom reported because of either the prohibitive cost of precious
metals (e. g. IrO2 and RuO2) or the instability of non-noble metals
in the acidic and strong oxidative conditions. More notably, the
proton exchange membrane (PEM) is currently commercially
available and PEM water electrolysis under acidic environment is
highly promising in large-scale hydrogen production duo to their
high current densities, high voltage efficiency, rapid system
response and acceptable partial load range.[3] Therefore, the
development of hydrolysis systems as well as corresponding low-
cost water splitting electrocatalysts of high activity and stability for
acidic electrocatalytic hydrogen production is of great significance
and importance, but remains a huge challenge.[1a, 4] Additionally,
anodic OER-produced O2 is less valuable and the resultant
mixture of H2/O2 produced by gas crossover during the water
decomposition may risk a danger of explosion.[5]
Alternatively, it is well known that catalysts may exhibit varied
activities and stabilities in different anodic reactions. Strategies of
small organic molecule oxidation-assisted water splitting for high-
efficient H2 production have emerged most recently, but mostly in
alkaline electrolytes, by utilizing low-cost reductive chemical
additives (e.g. urea, alcohols and aldehydes) as sacrificial agents
to substitute for the kinetic-slow OER, which can greatly lower the
cell voltage input and energy consumption, and can even be
expected to obtain high value-added oxidation products instead
of relative low value-added O2.[6] Therefore, non-noble metal
electrocatalysts in combination with organic molecule oxidation in
acidic electrolyte would be the most appealing and promising for
electrocatalytic hydrogen production. However, no reports on
electrolyzers operated in the acidic media by using conventional
metal oxides as electrode catalysts can be found to date, due to
Introduction
The rapidly increasing energy demand and environmental
pollution have stimulated intensive researches for developing
clean, efficient and scalable energy systems. Hydrogen
generated from electrochemical water splitting driven by
intermittent energy input is of great significance for the renewable
energy production, storage and utilization.[1] This process involves
two half reactions of hydrogen evolution reaction (HER) at the
cathode and oxygen evolution reaction (OER) at the anode. To
date, various cost-effective materials with excellent performance
1
This article is protected by copyright. All rights reserved.

10.1002/anie.202107510
Angewandte Chemie International Edition
RESEARCH ARTICLE
the well-known instability of most transition metal-based materials
in the electrocatalytic oxidation of organic compounds in acidic
electrolytes.
Scanning electron microscopic (SEM) (Figure 1a and 1b) and
transmission electron microscopic (TEM) (Figure 1c) images of
the obtained γ-MnO2 show a nanosheet morphology, which are
about ~3.24 nm in thickness as shown in atomic force microscopy
(AFM) image (Figure 1d). The side view SEM image and
corresponding linear scanning EDX results (Figure S1) reveal a
uniform and dense coverage of MnO2 material on acid-treated CP
surface of ~546 nm in thickness. The selected area electron
diffraction (SAED) pattern gives a polycrystalline phase structure
(Figure 1c, inset), which agrees well with the hereafter results of
the X-ray diffraction (XRD). High-resolution TEM (HRTEM) image
of MnO2 further identifies a lattice d-space of 0.248 nm that can
be indexed to the (021) lattice planes of γ-MnO2 (Figure 1e).
Additionally, elemental mappings indicate uniform spatial
distributions of Mn and O throughout the materials in the view
(Figure 1f and Figure S2), and the atomic ratio of manganese to
oxygen is 1:1.99, which is consistent with the subsequent X-ray
photoelectron spectroscopy (XPS) results.
Thanks to the low cost, earth abundance, low toxicity, rich
variation of Mn valence and special Mn-O octahedral field effect,
manganese dioxide is a promising electrocatalyst candidate, but
usually exhibits considerable compromise between activity and
durability and only moderate electrocatalytic performance can be
obtained in catalyzing OER in alkaline media, not to mention in
acidic electrolytes.[7] Herein, facile-synthesized manganese oxide
catalyst supported on carbon paper (donated as MnO2/CP) were
developed in coordination with alcohol oxidations for the efficient
and highly durable hydrogen production in acidic electrolytes
(Scheme 1). In this strategy, the oxidation of various alcohols
(e.g., glycerol, 1, 2-propanediol and ethylene glycol) were used to
substitute for OER, and these alcohols were decomposed into
value-added products of carboxylic acid compounds at the anode
at a far lower potential than that of OER, along with the promoted
H2 production at the cathode. Especially in the glycerol oxidation
reaction, a current density of 10 mA cm-2 can be achieved at a
potential of as low as 1.36 V versus reversible hydrogen electrode
(vs. RHE) in acidic aqueous solution, which is 270 mV lower than
that of OER. Meanwhile, high value-added liquid product of formic
acid, rather than oxygen, can be obtained at the anode to avoid
The crystalline structure of the prepared MnO2/CP was
characterized by XRD. As shown in Figure S3, the diffraction
peaks of low intensity except those belonging to graphite (JCPDS
no: 411487) from carbon paper can be indexed to (110), (021)
and (061) planes of γ-MnO2 phase.[8] XPS was employed to
further investigate the surface chemical components and valance
the potential risk of H2/O2 explosion in traditional water electrolysis. states of MnO2/CP (Figure S4). As presented in Figure S4b, the
Impressively and unexpectedly, the electrocatalytic hydrogen
production system equipped with MnO2/CP can be operated for
longer than 865 hours under the presence of glycerol, which only
lasted for less than 10 hours of OER catalyzed by the same
material. The valance state of Mn in MnO2/CP was slightly
increased after glycerol oxidation, but decreased markedly after
OER, suggesting that the addition of glycerol can not only reduce
the energy input, but also, actually more importantly, prevent the
deactivation of the catalyst. The analyses of in situ Raman and
DFT calculation demonstrate that the addition of glycerol can
enhance the stability of the material via the inhibition of lattice
oxygen process and MnO4- formation.
splitting of Mn 3s by the electron exchange interaction upon
photoelectron ejection, was used to determine the oxidation state
of Mn. The peak energy separation (ΔE) of the splitted Mn 3s in
MnO2/CP is 4.89 eV, which is slightly higher than those literature-
reported for MnO2. According to previous reports, lower valence
of manganese will lead to stronger separation of the 3s peaks,[9]
thus, the coexistence of Mn3+ and Mn4+ species in the MnO2/CP
catalyst can be qualitatively concluded, which is consistent with
the result of Mn 2p2/3 peak fitting result shown in Figure S4c
(detailed discussion are given in supporting information). Besides,
the high-resolution spectrum of O 1s as shown in Figure S4d can
be deconvolved into three sub-peaks located at 530.03 eV (O1),
531.55 eV (O2) and 533.21 eV (O3), which can be assigned to
lattice oxygen, oxygen vacancies and adsorbed oxygen species,
respectively.[10] Meanwhile, the presence of abundant oxygen
vacancies, which is usually correlated with the formation of Mn3+
species and oxygen evolution activity, has also been evidenced
Scheme 1. Schematic illustration of electrocatalytic H2 production from acidic
aqueous solution of glycerol.
Figure 1. Microscopic analyses of MnO2/CP catalysts. (a) Low- and (b) high-
magnification SEM images of MnO2/CP. (c) TEM image of MnO2/CP (the inset
shows the SAED pattern). (d) AFM image of MnO2/CP (the inset shows the
corresponding height profile). (e) HRTEM, (f) HAADF-STEM and the
corresponding EDS elemental mapping images of MnO2/CP.
Results and Discussion
Materials characterization
The MnO2 electrodes were grown in situ on conductive
carbon paper (CP) by a facile one-step electrodeposition method.
2
This article is protected by copyright. All rights reserved.

10.1002/anie.202107510
Angewandte Chemie International Edition
RESEARCH ARTICLE
by electron spin resonance (ESR) measurements as shown in
Figure S5.
(Figure 2d). For comparison, manganese oxide synthesized by
cyclic voltammetric cycles supported on CP (denoted as
MnO2/CP-CV) has also been evaluated under the same condition
(Figure S11). As shown in Figure S12, MnO2/CP shows a lower
onset potential than that of MnO2/CP-CV for GOR, indicating the
higher electrochemical GOR performance of the former. The
electrochemical impedance spectra (EIS) show a relatively lower
impedance of MnO2/CP, indicating the faster charge transfer on
the electrode surface (Figure S13a) than others. Furthermore,
the results of the double-layer capacitances (Cdl) calculated from
the cyclic voltammetry curves point to a smaller Cdl value of
MnO2/CP-CV (0.762 F cm-2) than that of MnO2/CP (0.909 F cm-2),
demonstrating a significantly larger electrochemical surface area
(ECSA) and denser exposed active sites of the catalyst MnO2/CP
synthesized by potentiostatic technique (Figure S13b-d).
To obtain the optimal GOR performance, the synthetic
parameters, such as the deposition time period, deposition
potential and the pretreatment of the carbon paper have been
modulated. Firstly, the electrocatalytic performances of
manganese oxides synthesized at varied deposition durations
(detailed information shown in Table S3) have been tested under
the same condition and the results are shown in Figure S14-15.
Apparently, the thicker-deposited MnO2 catalysts show higher
electrocatalytic activities than the thinner ones, as demonstrated
by the enhanced current densities at increased material loadings.
However, it should be noted that the 8.98 C cm-2 is the optimal
catalyst loading beyond which the activity of the catalyst reaches
a plateau, which can be attributed to the intrinsically limited
proton-electron transport and transfer rates in catalysts.[13] In
addition, the importance of carbon paper pretreatment for the
deposition of manganese oxides should be emphasized. As
evidenced in Table S4, the XPS results of the Acid-CP show the
increased oxygen amount on the surface of carbon paper after
acid treatment. When using the untreated CP (donated as UCP)
as substrate, the obtained MnO2/UCP shows a much lower
amount of charge passing-through (4.33 C cm-2) during the
electrodeposition than MnO2/CP (8.98 C cm-2), indicating an
inferior catalytic oxidation activity of glycerol and the important
role of the oxygen-containing groups on the CP surface for
anchoring the catalytic materials (Figure S16 and Table S3).[14]
Furthermore, a series of manganese oxide catalysts prepared at
varied deposition potentials have been investigated for GOR
(Figure S17). 0.6 V (vs SCE) has been selected as the optimal
potential for catalyst fabrication in terms of the catalytic activity
and energy consumption.
The effects of deposition potential on the composition, micro-
structure and valance states of the obtained catalysts have been
investigated by SEM, XRD (Figure S6 and S8) and XPS
measurements (Figure S7). As shown in Figure S7a and Table
S1, with the deposition potential increasing from 0.2 to 0.6 V vs.
SCE, the peak energy separation ΔE of the splitted Mn 3s
decreases from 5.35 eV to 4.89 eV, then remains almost
unchanged at further increased deposition potential from 0.6 to
1.0 V vs. SCE, suggesting a relatively lower ratio of Mn3+ to Mn4+
of the catalysts synthesized at the potentials higher than or equal
to 0.6 V vs SCE, which is also supported by the energy level
measurements of Mn 2p2/3 (Figure S7b and Table S2). Moreover,
all these results correspond well with the XRD results, that is, the
characteristic peak of γ-MnO2 can only be observed in the
manganese oxide catalysts deposited at higher than or equal to
0.6 V (Figure S8). Additionally, the XPS O1s spectra imply
enhanced density of oxygen vacancies in the catalysts at lowered
deposition potential (Figure S7c and Table S2), which
corresponds to the elevated ratio of Mn3+ to Mn4+ and the negative
effect of lowering deposition potential on the formation of γ-MnO2.
Electrochemical behavior
The electrocatalytic performance of MnO2/CP towards
various alcohols (glycerol, ethanol, ethylene glycol (EG), 1, 2-
propanediol (1, 2-P), 1, 3-propanediol (1, 3-P) and 1-propanol (1-
P)) oxidations was evaluated in 0.005 mol/L (donated as M)
H2SO4 at a scan rates of 2 mV s-1 using a typical three-electrode
configuration. As displayed in Figure 2a, all the current densities
obtained in various kinds of acidic aqueous solutions of alcohols
are markedly higher than that in alcohol-free electrolyte, among
which the glycerol-containing solution gives the highest current
density. According to these preliminary electrochemical
characterizations, glycerol was selected as the representative
candidate for further detailed studies. Figure S9 shows the liner
sweep voltammetry (LSV) curves obtained in 0.005 M H2SO4
containing varied concentrations of glycerol catalyzed by the
MnO2/CP. Apparently, MnO2/CP exhibits a relatively low current
density in the absence of glycerol, indicating a rather low OER
activity, whilst the current density increases along with the
increase of glycerol concentration and reaches the maximum at
0.2 M glycerol. Note that at the increased concentration of glycerol
above 0.30 M, the current density decreases probably due to the
poor conductivity of the mixed solution.[11] In order to further verify
the electrochemical activity of MnO2/CP, the LSV curves in the
absence and presence of 0.2 M glycerol were recorded subject to
the correction by iR compensation with respect to the solution
resistance as shown in Figure 2b. A current density of 10 mA cm-
2
can be achieved at an applied anodic potential of 1.36 V (vs.
RHE) for glycerol oxidation reaction (GOR), which is remarkably
270 mV lower than that for OER (1.63 V vs. RHE). Moreover, the
potential reductions for glycerol oxidation are at least 310 mV and
above to reach the current densities of 20, 40, 60 and 80 mA cm-
2, implying more favorable alcohol oxidation compared to OER at
elevated current densities (Figure 2c). Such anode potential
reductions are indeed appealing under acidic conditions in
comparison with previous literature reports even on precious
4d,
12]
metal catalysts[4c,
(Figure S10). Moreover, the
corresponding Tafel slope of GOR is 242.1 mV dec-1, which is also
much lower than that of OER (352.6 mV dec-1), demonstrating a
more favorable electrocatalytic kinetics of GOR than that of OER
3
This article is protected by copyright. All rights reserved.

10.1002/anie.202107510
Angewandte Chemie International Edition
RESEARCH ARTICLE
Figure 2 Electrocatalytic performances of the manganese oxide catalysts. (a) Polarization curves of MnO2/CP anode in the absence and presence of various kinds
of alcohols under acidic conditions at the scan rate of 2 mV s-1. (b) iR-corrected polarization curves of MnO2/CP anode in 0.005 M H2SO4 with and without the
addition of 0.2 M glycerol at the scan rate of 2 mV s-1. (c) Anodic potential comparison of MnO2/CP at varied current densities (10, 20, 40, 60 and 80 mA cm-2) in
0.005 M H2SO4 with and without the addition of 0.2 M glycerol. (d) Tafel plots for glycerol oxidation and OER derived from the LSV results. (e) Chronopotentiometric
curves of MnO2/CP for glycerol oxidation and OER at a constant current density of 10 mA cm-2. (f) Polarization curves over a MnO2/CP || Pt/C/CP electrolyzer with
and without the addition of 0.2 M glycerol addition. (g) Comparison between GC-measured and theoretically calculated H2 quantities. (h) Time dependences of the
electrolyzer voltage over a MnO2/CP || Pt/C/CP cell with and without the addition of 0.2 M glycerol at 10 mA cm-2.
It is well known that the long-term stability of anodic catalysts
under acidic conditions is a great challenge for electrocatalytic
water splitting, especially for non-precious metal electrocatalysts.
Therefore, the durability of MnO2/CP electrode for glycerol
oxidation and OER has been evaluated in low pH solutions with
and without glycerol addition by prolonged chronopotentiometric
assays at a constant current density of 10 mA cm-2. According to
the experimental results in Figure 2e, the high activity of the
MnO2/CP can be maintained for longer than 865 hours (still under
test) at a low potential of approximately 1.40 V vs RHE without
activity significant decay in 0.005 M H2SO4 solution with the
addition of 0.2 M glycerol. Long-term glycerol oxidation has also
been confirmed in stronger-acidic 0.05 M and 0.5 M H2SO4
solutions containing glycerol (Figure S18). Furthermore, the
MnO2/CP electrode also shows long-time stability at a much
elevated current density of 60 mA cm-2 (Figure S19). On the
contrary, the OER potential output can be maintained relatively
stable for only 10 and 1 h before soaring in the absence of glycerol
at 10 and 60 mA cm-2, respectively. Moreover, MnO2/CP also
shows remarkably higher stability in various alcohol-containing
electrolytes than that of OER in the absence of alcohol additions
(Figure S20). These results suggest that the coordinative
combination between manganese oxide catalyst and alcohol
oxidation can not only decrease the potential needed, but also
unexpectedly and extremely durably
electro-oxidize alcohol, especially glycerol, in strongly acidic
media for the concurrent electrochemical productions of hydrogen
and value-added chemicals.
In order to highlight the excellent performance of the γ-MnO2
electrode, other manganese dioxides of different crystalline
phases ( α-, β-, δ-, ε- and λ-MnO2) were also prepared (See
details in the supporting information) according to previously
reported methods[15] and characterized, and their performances
of glycerol electro-oxidation were tested. As shown in Figure S21,
4
This article is protected by copyright. All rights reserved.

10.1002/anie.202107510
Angewandte Chemie International Edition
RESEARCH ARTICLE
Based on the high activities and stabilities of MnO2/CP in
electrocatalytic hydrogen production system, the compositions of
the anodic reaction products after the addition of glycerol were
first analyzed by NMR after long time chronopotentiometry at the
constant current density of 10 mA cm-2 in 0.2 M glycerol aqueous
solution. As evidenced in Figure 3a and Figure S23a-23c, formic
acid, as the liquid product of glycerol oxidation, can be detected
by 1H and 13C NMR spectroscopy, featuring an average but highly
stable Faradic efficiency (FE) of ~53% in the long period (96 hours)
electrocatalytic glycerol oxidation process (Figure S23c), which
proves the excellent stability of the MnO2/CP electrode for the
generation of formic acid by glycerol oxidation under the
experimental
conditions.
Products
obtained
by
chronopotentiometry at varied current densities have also been
tested. The resultant FE and the selectivity towards formic acid
production are 47%~56% (Figure S23d) and 61%~68% (Figure
3b), respectively. Moreover, the gas products, namely CO2 and
CO, have also been produced according to the gas
chromatographic results, and their FEs and selectivity have been
calculated as presented in Figure 3b and Figure S23d. Moreover,
no oxygen can be detected at the anode electrode in the whole
potential range. The total faradaic efficiency values of up to 100%
for glycerol oxidation catalyzed by MnO2/CP suggest negligible
contributions of any other redox process to the total current.
Additionally, methane diol and formaldehyde can be detected by
13C NMR spectroscopy and phloroglucinol method (Figure S24),
which are considered as the intermediate products during the
bond breaking oxidation of glycerol in this work. In addition, the
oxidation products of other alcohols such as ethylene glycol were
also tested and analyzed as shown in Figure S26-27. In situ
Transform Infrared (FTIR) spectroscopy was adopted to further
shed light on the glycerol oxidation process (Figure 3c).The peak
at ~1740 cm-1 can be assigned to the formation of species
containing a carbonyl group, such as aldehydes and carbonyl
acids, which are hard to distinguish in the IR spectra because
almost all products of glycerol oxidation contain a carbonyl
group.[16] The absorption bands at ~1240, and ~1364 and ~1385
cm-1 are considered to belong to COOH.[17] Besides, the
asymmeteic (O-C-O) streching of COO-* (~ 1541 and ~1519 cm-
1) is visible in this spectrum.[18] According to analysis of in situ
FTIR and ex situ NMR results, a possible pathway of glycerol
oxidation catalyzed by MnO2/CP under acid condition is
proposed.[19] As illustrated by Figure S25, formic acid generated
by glycerol oxidation via the C-C bond cleavage may be further
oxidized into carbon monoxide and carbon dioxide. In another
path, formaldehyde formed by glycerol oxidation could be
hydrated to form methane diol, which can either be directly
oxidized to formic acid or re-adsorbed on the surface to form
COO-*, which can be further oxidized to carbon dioxide or carbon
monoxide.
Figure 3 Product analyses for glycerol oxidation. (a) 1H NMR spectra of
electrolyte before and after long-term anodic electrochemical test. Maleic acid
was added as an internal standard. Color codes: Formic acid (purple), glycerol
(blue), Maleic acid (yellow) and H2O (green). (b) Selectivities for formic acid,
CO2 and CO production at varied current densities. (c) In situ electrochemical
FTIR spectra of MnO2/CP at different potentials in an acidic glycerol solution.
the XRD patterns can be indexed to α-MnO2 (JCPDS 44-0141),
β-MnO2 (JCPDS 24-0735), δ-MnO2 (JCPDS 80-1098), ε-MnO2
(JCPDS 30-0820) and λ-MnO2 (JCPDS 44-0992) from top to
bottom, respectively. SEM images of these manganese dioxides
are displayed in Figure S22. The LSV curves for GOR catalyzed
by the different manganese dioxides show the highest activity of
γ-MnO2. Furthermore, the stability of these maganese oxide
samples for glycerol oxidation were tested in acidic solutions by
chronopotentiometric assays at 10 mA cm-2.The higher activity of
the γ-MnO2/CP can be maintained at the lower potential than
other catalysts, indicating the great potential of the γ-MnO2/CP in
this system.
With the excellent electrocatalytic performance of MnO2/CP
for the anodic GOR in hand, a two-electrode electrolyzer using
MnO2/CP as the anode and commercial Pt/C/CP as the cathode
has been assembled using a glycerol-added, acidic aqueous
electrolyte. As a contrast, conventional overall water electrolysis
was examined using the same system without any chemical
additive. As observed in Figure 2f, the electrolyzer in the
presence of glycerol requires a cell voltage of as low as 1.38 V to
reach the current density of 10 mA cm-2, leading to much lowered
energy input compared with that at the voltage up to 1.78 V
required in acidic aqueous solution without adding glycerol.
Additionally, the H2 amount generated at the cathode matches
well with the theoretical values, suggesting a Faraday efficiency
(FE) up to 100% (Figure 2g). Most importantly, the ultra-high
durability of MnO2/CP in acidic electrolyte with glycerol is further
verified by the sustained chronopotentiometry measurements,
where the operation voltage of 1.47 V can be maintained for over
45 h without significant increase. However, a rapid rise of voltage
is inevitable in pure water splitting in as short as 4 h, in
accordance with the general knowledge of poor stability of MnO2
in acidic media without the addition of glycerol (Figure 2h).
Mechanistic insight
5
This article is protected by copyright. All rights reserved.

10.1002/anie.202107510
Angewandte Chemie International Edition
RESEARCH ARTICLE
Figure 4 (a) SEM and (b) TEM images of the Post-GOR MnO2/CP. (c) SEM and (d) TEM images of Post-OER MnO2/CP. (e) Enlarged XPS spectra of Mn 3s of
as-prepared MnO2/CP, Post-GOR MnO2/CP and Post-OER MnO2/CP. (f) Fourier transforms of k3-weighted EXAFS experimental data of as-prepared MnO2/CP,
Post-GOR MnO2/CP and Post-OER MnO2/CP. Potential-dependent in situ Raman spectra of MnO2/CP collected without (g) and with (h) the addition of glycerol.
(i) in situ Raman spectra of MnO2/CP collected with and without glycerol at applied potential of 1.58 V. (j) ESR detection of formed hydroxyl radicals in electrolyte
during GOR and OER catalyzed by MnO2/CP. (k) Reaction free-energy diagram of OER (LOM) and glycerol oxidation to glyceraldehyde
The remarkably differentiated activities and stabilities of the
MnO2/CP electrode catalyst for GOR and OER strongly suggest
substantially different electro-catalytic pathways between the two
processes. To reveal such a difference, we first quantified the
dissolved Mn amounts during the GOR and OER by inductively
coupled plasma optical emission spectrometry (ICP-OES). In 24
h of electrolysis at 10 mA cm-2, the MnO2/CP catalyst after GOR
(Post-GOR MnO2/CP) shows a ~4.80% weight loss of Mn relative
the weight loss of MnO2/CP in acidic electrolytes under same
conditions without applying any potential (98.11%), implying the
dissolution of the MnO2 species at the positively charged anode
can be largely suppressed under the anodic electrochemical
conditions, as previously reported in literature. [13a] The SEM and
TEM images further reveal the different influences of these two
operations on the morphology of MnO2/CP electrode as
presented in Figure 4a-d and Figure S29. Moreover, the Post-
to the fresh MnO2/CP, which is markedly lower than that of ~10.48% GOR MnO2/CP remains its pristine γ-MnO2 structure as
of the MnO2/CP catalyst after OER (Post-OER MnO2/CP) (Figure
S28a). Similar results can be obtained from the measurements of
post-reaction catalysts operated at higher current densities
(Figure S28b). Note that all these values are obviously lower than
evidenced by XRD patterns (Figure S30), comparatively,
however, the XRD reflections of the Post-OER MnO2/CP
becomes weakened, implying the possible structural damage of
MnO2/CP during OER, which results in the poor stability.
6
This article is protected by copyright. All rights reserved.

10.1002/anie.202107510
Angewandte Chemie International Edition
RESEARCH ARTICLE
MnO2/CP electrode before and after the GOR/OER
operations have been characterized using ex situ XPS and X-ray
absorption spectroscopy (XAS) measurements to understand the
electronic changes occurring at the Mn and O centres during the
reaction process under acid conditions. As exhibited in Figure 4e
and Table S5, the peak energy separation (ΔE) between the two
peaks in the high-resolution Mn XPS spectrum of Post-GOR
MnO2/CP decreases slightly from 4.89 to 4.83 eV, revealing a
slightly increased valence state of Mn in the catalyst after GOR.
In contrast, the ΔE value of Post-OER MnO2/CP has been
measured to increase to 5.28 eV, suggesting a much lowered
valance state of the catalyst after OER, which is in accordance
with the introduction of abundant oxygen defects in the catalyst
as demonstrated by Figure S31 and Table S6. The Mn K-edge
X-ray adsorption near edge structure (XANES) spectra of Post-
OER MnO2/CP and Post-GOR MnO2/CP (Figure S32) display
negligible and significantly positive changes relative to their initial
state, respectively, further confirming the above results.[20] Further
structural information was obtained by extended X-ray absorption
fine structure (EXAFS) measurement to understand the
configuration and local coordination environment (Figure 4f,
Figure S33 and Table S7).[21] Figure 4f shows two peaks at
around 1.89 Å and 2.85 Å in R-space spectra, which are
originated from the Mn-O and Mn-Mn bonds, respectively. The
fitting results show a larger oxygen coordination number (4.3) to
Mn in Post-GOR MnO2/CP and a smaller one (3.9) to Mn in Post-
OER MnO2/CP than that of the as-prepared MnO2/CP,
respectively, indicating an opposite change of oxygen defect
concentration during these two reactions,[20, 22] which agree well
with the O 1s XPS data.
at 566 cm-1 and a relatively weak peak 380 cm-1 can be observed
which can be attributed to the in-plane stretching vibrations of
octahedral layers in MnO2 and the terminal Mn-O(H) tunnel or
surface stretches, respectively, implying the possible adsorption
of water molecules. With the increase of applied potential up to
-
1.58 V, the peak at 833cm-1 ascribed to the MnO4 species
appears and further intensifies gradually at and above 1.68 V,
which will de-stablize the catalyst.[24]
In situ Raman spectroscopic results obtained in the
electrolyte with the addition of glycerol are shown in Figure 4h.
Similarly, the species of Mn-O(H) can also be observed at 1.08 V.
However, compared to that without the glycerol addition, no peak
of MnO4- can be found at the increased potential applied, which is
a clear evidence for the excellent stability of GOR. Figure 4i
compares the results between with (GOR) and without (OER)
glycerol at the potential of 1.58 V. A relatively strong spectral band
at around 800 cm-1 belonging to Mn-oxo (MnIV=O oxygen
species)[25] could be observed during OER. In the presence of
glycerol, however, the peak intensity at around 800cm-1 is
significantly lower than that in the OER, and no signal belonging
to MnO4- can be found, indicating the substantial protection effect
of glycerol molecules against MnIV=O complex oxidation into
-
MnO4 soluble in the electrolyte, and the resultant excellent
durability of the MnO2/CP catalyst.
According to experiment results and literature reports[26], the
possible mechanisms of GOR and OER catalyzed by MnO2/CP
catalysts under acidic conditions are proposed as shown in
Scheme 2. It is well known that H2O in electrolyte will be adsorbed
on the metal oxides at anode and then lose electrons to form a
hydroxyl radical-adsorbed species (MnOx(-OH)) benefitting from
the abundant d-orbitals of Mn element under the action of surface
electric field. The absorbed hydroxyl radicals will react with
oxygen atoms in the lattice of manganese oxide to form MnOx+1
owing to the strong Mn-OH bonding.[27] O2 is then released from
this chemical adsorbed “active oxygen” in MnOx+1, which takes
away one oxygen atom from the lattice. This process is
considered as the lattice oxygen mechanism (LOM, a process
usually taking place with metal dissolution and V0 formation and
thus leading to catalyst structural damage), which, together with
To further investigate the mechanism of GOR and OER over
MnO2/CP anode, in situ electrochemical Raman spectra were
obtained in acidic solutions with and without the glycerol addition.
Figure 4g displays the potential-dependent Raman spectral
traces of MnO2/CP catalyst for OER. According to a previous
report, the bands in the region of about 490 - 700 cm-1 can be
interpreted as the stretching vibrations of MnO6 octahedra and the
2- [23]
sharp peak located at 975 cm-1 corresponds to SO4
.
Upon
elevating the applied potential to 1.08 V vs. RHE, a strong peak
Sheme 2. Schematics of the proposed mechanism for GOR and OER on MnOx/CP catalysts in acid media
7
This article is protected by copyright. All rights reserved.

10.1002/anie.202107510
Angewandte Chemie International Edition
RESEARCH ARTICLE
the conventional adsorbate evolution mechanism, are considered
to be the most accepted two routes for the structural instability
during acidic OER.[3a] In addition, the catalyst will dissolve as
alcohols possessing hydroxyl groups on adjacent carbon show
significantly reduced anodic potential and excellent stability
compared with traditional electrocatalytic water splitting. In
particular, the electrocatalytic glycerol oxidation in coupling with
water reduction not only enables the efficient productions of
hydrogen and value-added formic acid instead of oxygen, but can
also be operated at an especially low potential (1.36 V vs. RHE)
for more than 865 hours, which is greatly longer than that in the
absence of glycerol. The presence of alcohol molecules, such as
glycerol, has been proposed to protect the catalyst from
degradation by stabilizing the manganese valence and
diminishing the excessive oxygen vacancies, therefore favoring
the ultra-long stability of MnO2/CP. The in situ Raman
spectroscopic analysis and DFT calculation further manifest the
effect of glycerol addition on enhancing the stability of MnO2 via
the inhibitions of both lattice oxygen process and MnO2
dissolution. Such a finding may open an unprecedented window
in searching novel non-noble metal catalysts for applications in
electrochemical hydrogen and value-added chemical productions
by alcohol oxidation under acidic conditions.
-
MnO4 (the species derived from the further MnIV=O complex
oxidation) in the electrolyte at the potential higher than 1.58 V. As
a result, the electrocatalytic activity of MnO2/CP catalyst will be
substantially deteriorated during this OER process because of not
only the significant decrease of Mn valence state and the
noticeable increase of oxygen vacancy concentrations in the
above experimental results, but also the further oxidation of
−
MnIV=O into soluble MnO4 species. Once added, glycerol
molecule possessing stronger reducing potential than water is
believed to be preferably anchored on the MnO2 owing to its
strong electron donation capability to the positively charged
anodic catalyst during the electrolytic operation. Such anchored
glycerol molecules can not only shield the catalyst against the
dissolution by preferentially interacting with MnIV=O to prevent its
-
further oxidation into MnO4 , but more importantly, they can also
prevent the formation of chemisorbed oxygen (an important step
in producing oxygen leading to the destruction of the catalyst). As
a result, the oxide catalyst is protected from deterioration via the
glycerol adsorbing, while the adsorbed glycerol will be oxidized
more favorably than water to form carbonaceous chemicals
instead of oxygen by water oxidation, due to the stronger
reductive potential of glycerol than water on the electrode. This
pathway of preferred glycerol oxidation can be supported by the
much higher concentration of hydroxyl radicals produced in post-
GOR electrolyte than that in post-OER electrolyte observed by
ESR (Figure 4j).[28]
Supporting Information
Supporting Information is available from the Wiley Online Library
or from the author.
Density functional theory (DFT) calculations were carried out
to further support the above mechanisms. On the basis of the
characterization results, the surface of the prepared catalyst was
characterized by a MnO2 (021) model. Since the oxidation of
glycerol is a multi-step process, the calculation has been
simplified to only acount for the oxidation of glycerol to
glyceraldehyde to compare with the OER process via LOM. As
shown in Figure 4k, the reaction branches after the formation of
*O intermediate, and the energy barrier to form *OOL (ΔG = 2.43
eV) is significantly higher than that for RCHOHO* (ΔG = -0.36 eV).
The DFT results demonstrate that in the presense of RCH2OH
(R=CH2OHCHOH), the produced *O intermediate will react with
the RCH2OH to produce RCHO instead of coupling with lattice
oxygen to produce O2, in consistence with the experimental
results. Collectively, in acidic aqueous solutions without the
addition of glycerol, besides the dissolution of the MnO2 by
Acknowledgements
This work was supported by Natural Science Foundation of
Shanghai (21ZR1418700), China Postdoctoral Science
Foundation funded project (2020T130193). The authors would
like to thank ECNU Multifunctional Platform for Innovation for
support of SEM and TEM characterizations (004). The authors
thank beamline BL14W1 (Shanghai Synchrotron Radiation
Facility) for providing the beam time). We gratefully acknowledge
Dr. Yuan Yuan at the East China Normal University for his help
with the Raman analysis.
Keywords: acidic electrolyte • non-noble metal • manganese
oxide catalyst • glycerol oxidation reaction • electrocatalytic
hydrogen production
−
forming MnO4 soluble in electrolyte, lattice structure of catalyst
[1]
[2]
[3]
a) M. Blasco-Ahicart, J. Soriano-López, J. J. Carbó, J. M. Poblet, J.
R. Galan-Mascaros, Nat. Chem. 2017, 10, 24-30.; b) H. Xu, H.
Shang, C. Wang, Y. Du, Coord. Chem. Rev. 2020, 418, 213374.
a) H. Xu, H. Shang, L. Jin, C. Chen, C. Wang, Y. Du, J. Mater. Chem.
A 2019, 7, 26905-26910; b) H. Xu, H. Shang, C. Wang, L. Jin, C.
Chen, C. Wang, Y. Du, Appl. Catal. B 2020, 265, 118605.
will become gradually collapsed due to the high concentration of
oxygen vacancies created in the MnO2 lattice; while the
introduction of reductive glycerol can protect the catalyst from
deactivation by inhibiting both LOM and the MnIV=O oxidation into
MnO4 , thus favouring the long-term stability of the MnO2/CP at
anode in electrocatlytic hydrogen production system.
-
a) L. An, C. Wei, M. Lu, H. Liu, Y. Chen, G. G. Scherer, A. C. Fisher,
P. Xi, Z. J. Xu, C. H. Yan, Adv. Mater. 2021, 33, e2006328; b) M.
Carmo, D. L. Fritz, J. Mergel, D. Stolten, Int. J. Hydrogen Energ.
2013, 38, 4901-4934.
Conclusion
[4]
a) P. Li, R. Zhao, H. Chen, H. Wang, P. Wei, H. Huang, Q. Liu, T.
Li, X. Shi, Y. Zhang, M. Liu, X. Sun, Small 2019, 15, 1805103; b) Y.
Li, X. Wei, L. Chen, J. Shi, Angew. Chem. Int. Ed. 2021, 60, 2-24.;
c) G. Wu, X. Zheng, P. Cui, H. Jiang, X. Wang, Y. Qu, W. Chen, Y.
Lin, H. Li, X. Han, Y. Hu, P. Liu, Q. Zhang, J. Ge, Y. Yao, R. Sun, Y.
Wu, L. Gu, X. Hong, Y. Li, Nat. Commun. 2019, 10, 4855; d) M.
Chatti, J. L. Gardiner, M. Fournier, B. Johannessen, T. Williams, T.
In summary, non-precious metal MnO2/CP electrocatalyst in
coordination with alcohol oxidation demonstrate not only
significantly decreased total energy input for hydrogen production,
but also unexpected but most favorable ultra-long durability in
acidic electrolytes. Especially, the electrocatalytic oxidations of
8
This article is protected by copyright. All rights reserved.

10.1002/anie.202107510
Angewandte Chemie International Edition
RESEARCH ARTICLE
R. Gengenbach, N. Pai, C. Nguyen, D. R. MacFarlane, R. K.
Stern, K. A. Macor, D. Kim, J. T. Groves, and T. G. Spiro, J. Am.
Chem. Soc. 1988 110 (13), 4158-4165.
Hocking, A. N. Simonov, Nat. Catal. 2019, 2, 457-465.
[5]
[6]
B. You, X. Liu, N. Jiang, Y. Sun, J. Am. Chem. Soc. 2016, 138,
13639-13646.
[26]
[27]
K. Jin, H. Seo, T. Hayashi, M. Balamurugan, D. Jeong, Y. K. Go, J.
S. Hong, K. H. Cho, H. Kakizaki, N. Bonnet-Mercier, M. G. Kim, S.
H. Kim, R. Nakamura, K. T. Nam, J. Am. Chem. Soc. 2017, 139,
2277-2285.
a) X. Wei, S. Wang, Z. Hua, L. Chen, J. Shi, ACS Appl. Mater.
Interfaces 2018, 10, 25422-25428; b) Y. Huang, X. Chong, C. Liu,
Y. Liang, B. Zhang, Angew. Chem. Int. Ed. 2018, 57, 13163; c) Y.
Li, X. Wei, L. Chen, J. Shi, M. He, Nat. Commun. 2019, 10. 5335.
a) M. Huynh, C. Shi, S. J. L. Billinge, D. G. Nocera, J. Am. Chem.
Soc. 2015, 137, 14887-14904; b) Y. Tang, S. Zheng, S. Cao, H. Xue,
H. Pang, J. Mater. Chem. A 2020, 8, 18492-18514; c) H. Wang, F.
Yin, B. Chen, G. Li, J. Mater. Chem. A 2015, 3, 16168-16176; d) A.
Li, H. Ooka, N. Bonnet, T. Hayashi, Y. Sun, Q. Jiang, C. Li, H. Han,
R. Nakamura, Angew. Chem. Int. Ed. 2019, 58, 5054-5058; e) R.
Frydendal, E. A. Paoli, I. Chorkendorff, J. Rossmeisl, I. E. L.
Stephens, Adv. Energy Mate. 2015, 5, 1500991.
R. Subbaraman, D. Tripkovic, K. C. Chang, D. Strmcnik, A. P.
Paulikas, P. Hirunsit, M. Chan, J. Greeley, V. Stamenkovic, N. M.
Markovic, Nat. Mater. 2012, 11, 550-557.
[7]
[28]
.
G. Chen, Sep. Pur. Technol. 2004, 38, 11-41.
[8]
[9]
a) C. Y, and J. Parmetier, et al. , Progress in Solid State Chemistry
1995, 23, 1-130; b) S. Chou, F. Cheng, J. Chen, J. Power Sources
2006, 162, 727-734.
a) M. C. a. M. Ishikawa, J. Electrochem. Soc. 2000, 147 2246-2251 ;
b) Mathieu Toupin, Chem. Mater. 2002, 14, 3946-3952; c) Cerrato,
J. M., Hochella, M. F., Knocke, W. R., Dietrich, A. M. & Cromer, T.
F; Environ. Sci. Technol. 2010, 44, 5881–5886; d) P. Gao, P. Metz,
T. Hey, Y. Gong, D. Liu, D. D. Edwards, J. Y. Howe, R. Huang, S.
T. Misture, Nat. Commun. 2017, 8, 14559.
[10]
a) H. Tian, L. Zeng, Y. Huang, Z. Ma, G. Meng, L. Peng, C. Chen,
X. Cui, J. Shi, Nano-Micro Lett. 2020, 12, 161; b) S. Gao, Z. Sun, W.
Liu, X. Jiao, X. Zu, Q. Hu, Y. Sun, T. Yao, W. Zhang, S. Wei, Y. Xie,
Nat. Commun. 2017, 8, 14503.
[11]
[12]
[13]
K. Xiang, D. Wu, X. Deng, M. Li, S. Chen, P. Hao, X. Guo, J. L. Luo,
X. Z. Fu, Adv. Funct. Mater. 2020, 30, 1909610.
N. Li. T. P. Keane, S. S. Veroneaua, R. G. Hadt, D. Hadt, L. X. Chen,
D. G. Nocera, PNAS 2020, 117, 16187-16192.
a) M. Huynh, D. K. Bediako, D. G. Nocera, J. Am. Chem. Soc. 2014,
136, 6002-6010; b) D. K. Bediako, C. C. Costentin, E. C. Jones, D.
G. Nocera, J. Savꢀant, J. Am. Chem. Soc. 2013, 135, 10492-10502.
A. Wu, Y. Xie, H. Ma, C. Tian, Y. Gu, H. Yan, X. Zhang, G. Yang, H.
Fu, Nano Energy 2018, 44, 353-363.
[14]
[15]
a) Liang, S., Teng, F., Bulgan, G., Zong, R. Zhu, Y, J. Phys. Chem.
C 112, 5307-5315 ; b) E. Hayashi, Y. Yamaguchi, K. Kamata, N.
Tsunoda, Y. Kumagai, F. Oba, M. Hara, J. Am. Chem. Soc. 2019,
141, 890-900; c) W. Wei, X. Cui, W. Chen, D. G. Ivey, J. Power
Sources 2009, 186, 543-550.
[16]
[17]
L. Huang, Y. Sun, H. Cao, M. Zhan, R. Ni, J. Sun, Z. Chen, Y. Zhou,
E. G. Sorte, J. Tong, G. Sun, ACS Catal. 2016, 6, 7686-7695.
M. S. E. Houache, R. Safari, U. O. Nwabara, T. Rafaïdeen, G. A.
Botton, P. J. A. Kenis, S. Baranton, C. Coutanceau, E. A. Baranova,
ACS Appl. Energy. Mater. 2020, 3, 8725-8738.
[18]
[19]
N. J. Firet, W. A. Smith, ACS Catal. 2016, 7, 606-612.
a) Y. Kwon, Y. Birdja, I. Spanos, P. Rodriguez, M. T. M. Koper, ACS
Catal. 2012, 2, 759-764; b) P. Pullanikat, J. H. Lee, K. S. Yoo, K. W.
Jung, Tetrahedron Lett. 2013, 54, 4463-4466; c.
[20]
[21]
Y. Zhao, C. Chang, F. Teng, Y. Zhao, G. Chen, R. Shi, G. I. N.
Waterhouse, W. Huang, T. Zhang, Adv. Energy Mater. 2017, 7,
1700005.
S. Lian, M. P. Browne, C. Domínguez, S. N. Stamatin, H. Nolan, G.
S. Duesberg, M. E. G. Lyons, E. Fonda, P. E. Colavita, Sustain.
Energ. Fuels 2017, 1, 780-788.
[22]
[23]
[24]
X. Li, J. Ma, L. Yang, G. He, C. Zhang, R. Zhang, H. He, Environ.
Sci. technol. 2018, 52, 12685-12696.
D. Chen, D. Ding, X. Li, G. H. Waller, X. Xiong, M. A. El-Sayed, M.
Liu, Chem. Mater. 2015, 27, 6608-6619.
a) K. H. Cho, S. Park, H. Seo, S. Choi, M. Y. Lee, C. Ko, K. T.
Nam, Angew. Chem. Int. Ed. 2021, 60, 4673; b) W. Kiefer, H. J.
Bernstein, Mol. Phys. 2006, 23, 835-851.
[25]
a) S. C. Sawant, X. Wu, J. Cho, K. B. Cho, S. H. Kim, M. S. Seo, Y.
M. Lee, M. Kubo, T. Ogura, S. Shaik, W. Nam, Angew. Chem. Int.
Ed. 2010, 49, 8190-8194; b) R. S. Czernuszewicz, Y. O. Su, M. K.
9
This article is protected by copyright. All rights reserved.

10.1002/anie.202107510
Angewandte Chemie International Edition
RESEARCH ARTICLE
Entry for the Table of Contents
This work reports a strategy of using low-cost acidic aqueous solution of alcohols for efficient hydrogen/chemical co-production. The
as-prepared non-precious metal MnO2/CP electrocatalyst in coordination with alcohol oxidation demonstrate not only significantly
decreased total energy input for hydrogen production, but also ultra-high durability in acidic electrolytes.
10
This article is protected by copyright. All rights reserved.