Using nickel manganese oxide catalysts for efficient water oxidation

Article abstract of DOI:10.1039/c4cc09671a

Nickel-manganese oxides with variable Ni : Mn ratios, synthesised from heterobimetallic single-source precursors, turned out to be efficient water oxidation catalysts. They were subjected to oxidant-driven, photo- and electro-catalytic water oxidation showing superior activity and remarkable stability. In addition, a structure-activity relation could be established.

Full text of DOI:10.1039/c4cc09671a

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Using nickel manganese oxide catalysts for efficient
water oxidation
Cite this: DOI: 10.1039/x0xx00000x
Prashanth W. Menezes,a Arindam Indra,a Ophir Levy,a Kamalakannan Kailasam,a
Vitaly Gutkin,b Johannes Pfrommer,a and Matthias Driess*a
Received 00th xxxxxxx,
Accepted 00th xxxxxxx
DOI: 10.1039/x0xx00000x
www.rsc.org/
Nickel-manganese oxides with variable Ni:Mn ratios, have not been studied as yet. Therefore, we opted for the singleꢀ
synthesised from heterobimetallic single-source precursors, source precursor (SSP) approach to gain access to a new class of
turned out to be efficient water oxidation catalysts. They were heterobimetallic nickel manganese oxides versus nickel oxide as
subjected to oxidant-driven, photo- and electro-catalytic promising catalysts for efficient oxidantꢀdriven, photoꢀ and electroꢀ
water oxidation showing superior activity and remarkable catalytic water oxidation.
stability. In addition, a structure-activity relation could be
established.
First of all, nickel manganese and nickel oxalate SSPs were
prepared in microꢀemulsions containing cetyltrimethylammonium
bromide (CTAB) as a surfactant, 1ꢀhexanol as coꢀsurfactant and
hexane as the lipophilic phase and mixed with aqueous solution
containing Ni2+, Mn2+ and oxalate ions with tuneable ratios.13 The
thus yielded oxalate SSPs were treated thermally in the presence of
dioxygen to form the respective oxide phases of various
morphologies. (see ESI, synthesis). The latter method is a reliable
ways to access these lowꢀcost materials in multigramꢀscale
quantities.
All precursors were characterised extensively by stateꢀofꢀtheꢀart
techniques and the corresponding data are given in Figures S1ꢀS9
and Tables S1ꢀS2, respectively. The thermal degradation of the
different heterobimetallic NiMn and homometallic Ni precursors in
the presence of dioxygen produced the pure oxides phases Ni6MnO8
(JCPDS 42ꢀ479), MnNi2O4 (JCPDS 36ꢀ83), NiMn2O4 (JCPDS 1ꢀ
1110) and NiO (JCPDS 71ꢀ1179), respectively, as confirmed by
Powder XꢀRay Diffraction (PXRD) analysis (Fig. S10). The
chemical composition, quantification of Ni:Mn ratio and their
presence in the phase was obtained by Inductively Coupled Plasma
(ICP) Atomic Emission Spectroscopy (AES) and Energy Dispersive
Xꢀray (EDX) analysis (Fig. S11 and Table S3). Interestingly, just by
tuning the nickel and manganese ratio, various morphologies have
been realised. As shown in Figure 1, the higher magnification
Scanning Electron Microscopy (SEM) images of Ni6MnO8 showed a
flowerꢀtype morphology (∼1 µm) which consisted petals assembled
from nanoparticles and MnNi2O4 displayed cubic type particles.
NiMn2O4 forms small nanochains whereas NiO exhibits bricks
(∼400 nm) built of tiny nanoparticles (see also Fig.S12). Further
insights on the morphology and particles size were gathered by
Splitting of water by an efficient catalyst is one of the major aspects
of renewable energy research at present.1 Discovery of such highly
active catalysts with scalable, abundant, robust, stable and lowꢀcost
materials is a promising solution for the sustainable production of
clean energy.2 Over the years, firstꢀrow transition metal oxides,
particularly those with manganese oxide based systems have been
widely investigated for photoꢀ and electrochemical reactions,3, 4 not
only due to their economic and environmental benefits but also
because of the fact that nature enables solar to chemical energy
conversion with a Mn4CaO5 cluster of photosystem II (PS II).5
In this context, several manganese oxides have been extensively
explored for oxidantꢀdriven, photoꢀcatalytic and electroꢀcatalytic
water oxidation especially with nanocrystalline and amorphous
manganese and calcium manganese oxides.6ꢀ11 Recently, we
investigated different routes for the synthesis of various manganese
oxides for efficient water oxidation.12,13 On the other hand, nickel
based materials have drawn particular attention due to their earth
abundant nature as well as their lower water oxidation potentials for
efficient water oxidation catalysis.14ꢀ18 Although, we were successful
in substitution of cobalt in manganese oxides for enhanced redox
oxygen catalysis,19 the role of nickel in manganese oxide has been
merely examined. This is indeed because of the difficulties involved
in the synthesis and the precise control over the composition with a
maximum of dispersion of the nickel and manganese on the atomic
level, and of the oxidation states of the metals. A while ago,
Fukuzumi et al. reported a NiMnO3 phase toward water oxidation20
but other Ni:Mn ratios (compositions) of nickel manganese oxides
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DOI: 10.1039/C4CC09671A
Transmission Electron Microscopy (TEM) and High Resolution
The photoꢀcatalytic water oxidation was performed in a
(HR) TEM images (Fig. S13). In all cases the particles were well phosphate buffer solution of pH 7 in the presence of [Ru(bpy)3]2+
2ꢀ
crystalline with particle size of about 2ꢀ5 nm for Ni6MnO8, ∼50 nm (bpy = 2,2′ꢀbipyridine) as a photosensitiser and S2O8 as two
for MnNi2O4, ∼10 nm for NiMn2O4, and ∼5ꢀ10 nm for NiO, electron acceptor (Scheme S1). In a similar trend to the oxidantꢀ
respectively. The Fourier Transform Infrared (FTIR) spectrum of all driven water oxidation, the highest rate of oxygen evolution was
oxides is typical and characteristic for metal oxalates (Fig. S14). The exhibited by the nickelꢀrich Ni6MnO8 with a value of 1.00
highest BrunauerꢀEmmettꢀTeller (BET) surface area was displayed mmolO2molMꢀ1sꢀ1 that was again 1.5 times higher than the other
for Ni6MnO8 (51.9 m2/g) followed by NiMn2O4 (39.6 m2/g), NiO nickelꢀrich MnNi2O4 phase (0.69 mmolO2molMꢀ1sꢀ1) (Fig. 2). The rate
(30.4 m2/g), and MnNi2O4 (29.3 m2/g), respectively (Fig. S15).
of oxygen evolution for the nickelꢀdiluted NiMn2O4 was 0.44
mmolO2molMꢀ1sꢀ1 while NiO showed only a limited activity (0.07
mmolO2molMꢀ1sꢀ1). To compare the photoꢀcatalytic activity, the
commercial manganese oxides and nickel oxide were measured as
standards that again showed that asꢀsynthesised catalysts are highly
active and of interest (Fig. S21). Surface normalisation discloses that
the values for MnNi2O4 are superior to Ni6MnO8 > NiMn2O4 >> NiO
due to their lower surface area (Fig. S22). Comparison of the mass
and surface normalised activity with other reported catalysts
confirmed that the dilutedꢀmanganese oxide based Ni systems
produced higher oxygen evolution than most of the known active
nickel and manganese based catalysts (Table S4).7ꢀ10,20
After the Clark electrode experiments, a set of experiments for
longer duration was also carried out separately (see ESI) and the
oxygen gas was collected in the head space of the reaction mixture
Fig. 1. SEM images of (a) Ni6MnO8, (b) MnNi2O4, (c) NiMn2O4 (d) was quantitatively analysed by a gas chromatograph (GC). A
NiO.
maximum oxygen yield of 0.08 mLhꢀ1 of O2 was detected for
Ni6MnO8 and 0.07 mLhꢀ1 for MnNi2O4 (Table S5). Moreover, it is
The detailed bonding states of Ni, Mn and O were further not enough to have catalysts that are extremely active but one of the
characterised by Xꢀray Photoelectron Spectroscopy (XPS). The XPS indispensible criteria is also to know the fate of the catalyst after the
core level spectra of Ni2p3/2 and Ni2p1/2 for Ni6MnO8, NiMn2O4 and photoꢀcatalytic experiments, and therefore, PXRD and HRTEM
NiO exhibited peaks at binding energy (BE) of ~854.5 eV and 872.2 investigation were conducted on high performance Ni6MnO8 and
eV corresponding to Ni2+ while the peaks of MnNi2O4 shifted to the MnNi2O4 catalysts. From PXRD and HRTEM images (Fig. S23), it
higher energy of 856 eV and 873.8 eV which can be assigned as the is clear that the crystallinity and the morphology of the nickelꢀrich
mixture of Ni2+/3+ (Fig. S16).21 The Mn2p spectra of Ni6MnO8 and manganese oxides catalysts were preserved and stayed intact
MnNi2O4 displayed two major peaks for Mn2p3/2 and Mn2p1/2 at BE unveiling the enhanced stability.
~643.5 eV and ~655.0 eV that are consistent Mn4+ species whereas
for NiMn2O4, the peak positions were shifted to lower energy of
642.4 eV and 653.9 eV and are characteristic for Mn3+ (Fig. S17).22
The O1s spectrum for all oxides exhibited a major O2ꢀ peak
assignable to bridging oxides with two smaller ones that could be
attributed to the surface oxygen, physiꢀ and chemisorbed water at or
near the surface and to the hydroxide species (Fig. S18).19
Oxidantꢀdriven water oxidation experiments (see ESI for details)
were conducted with all catalysts (Fig. S19) in deoxygenated
aqueous solution of 0.5 M ceric ammonium nitrate (CAN) and the
rate of the oxygen evolution was calculated from the slope of the
linear fitting for the first 60 s. The Ni6MnO8 was found to be
extremely active with a maximum rate of 1.41 mmolO2molMꢀ1sꢀ1
considering both nickel and manganese atoms are active, and was
Fig. 2. Dissolved oxygen concentration profiles measured by Clark
approximately thrice higher than the MnNi2O4 (0.52 mmolO2molMꢀ1sꢀ
2ꢀ
electrode containing NiMnꢀ and Niꢀoxide catalysts in S2O8
Ru(bpy)3 system using phosphate (pH 7) buffer (300 W Xe lamp
with 395 nm cutꢀoff filter).
–
1). However, for NiMn2O4, the rate was far lesser with the value of
0.19 mmolO2molMꢀ1sꢀ1 and is comparable with the pure NiO (0.15
mmolO2molMꢀ1sꢀ1). The surface area and the total number of active
sites present on the catalyst play a crucial role in water oxidation.
Therefore, the correlation of surface area normalised plots is shown
in Fig. S20 and follows the same trend as that of total mass activity.
2+
The electroꢀcatalytic measurements (see ESI) were performed in
alkaline 0.1 M KOH solution using Cyclic Voltammetry (CV) at a
scan rate of 20 mV/s. The current for all electrodes were initially
increased during the first few cycles and reached a steady value after
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50 cycles (Fig. S24), and then stayed stable and were unchanged current values for NiO and NiMn2O4 were maintained over the
even after additional cycling. As shown in Fig. 3, For Ni6MnO8, the period of 15 hours. In the case of Ni6MnO8, increased current values
anodic current started growing at 1.54 (vs the reversible hydrogen were achieved demonstrating the exceptional stability of catalysts on
electrode, RHE). The maximum current density of 5.85 mAcmꢀ2 was a long run. On the other hand, a slight decrease in currents was
attained at 1.87 V. Similarly, for the MnNi2O4 and NiMn2O4, the observed for MnNi2O4.
current started increasing at 1.58 and 1.60 V, and the highest current
After the longꢀterm stability tests, the electrodes were further
density was achieved at 2.83 mAcmꢀ2 and 1.25 mAcmꢀ2 at 1.87 V, characterised by TEM and CV. HRTEM images of NiO, Ni6MnO8
respectively. Interestingly, for NiO, the current started growing at and MnNi2O4 revealed that an amorphous shell of NiOOH appears
1.40 V itself and the CV’s featured a pair of anodic and cathodic on the surface of the catalysts, which has already been well
peaks centred ∼1.5 V vs. RHE corresponding to the oxidation of NiO described for the Ni based catalysts (Fig. S29).16,23 After
(NiO + OHꢀ – 1eꢀ → NiOOH), followed by a current due to O2 chronoamperometry, the NiO electrode was subjected to CV
evolution.23 Electrodes were also preꢀconditioned and forward and attaining a lower overpotential (370 mV at 1 mAcmꢀ1) with slightly
backward scans were performed, with respect to the NiO/NiOOH lower current density, which unveils the impressive nature of the
redox reaction of NiO (Fig. S25).16,24 It could also be seen that for catalyst with prolonged durability (Fig. 30). In addition to the
the Ni6MnO8, MnNi2O4 and NiMn2O4, a small redox peak exists, alkaline media, the NiO catalyst was also studied in neutral (pH 7)
suggesting the partial oxidation of NiO to NiOOH in the nickel and slightly basic (pH 9) conditions using phosphate and borate
manganese catalysts. The estimated overpotential for water oxidation buffers and in KOH solution of pH 11, but only resulting into lower
at 1 mAcmꢀ2 for NiO was 395 mV while Ni6MnO8, MnNi2O4 activity (Fig. S31). The determined Tafel slope at pH 11 was lower
NiMn2O4 displayed an overpotential of 480, 560 and 610 mV, than pH 13 elucidating slower kinetics at lower pH (Fig. S32).
respectively (Table S6). The overpotential obtained for NiO here is
Based on the higher activity of nickelꢀrich manganese oxides
slightly higher than the highly active ultraꢀsmall NiO nanoparticles for oxidantꢀdriven and photoꢀcatalytic water oxidation (Ni6MnO8 >
but lesser than other known NiO as well as Ni(OH)2 nanoplates and MnNi2O4 > NiMn2O4 > NiO), and conversely, nickel oxide (NiO >
nanoparticles (see also Table S7).16ꢀ18,23,25,26 Also similar trend was Ni6MnO8 > MnNi2O4 > NiMn2O4) for electrochemical OER, a
extended when normalised with the surface area suggesting that structure activity relation can be deduced. The crystal structure of
more active sites are available on the surface of NiO than the nickel Ni6MnO8 is cubic (space group Fm3m) and may be considered as
manganese oxides (Fig. S26). Tafel slopes were extracted in the rockꢀsalt structure where 6/8 of octahedral sites are occupied by Ni2+
potential range of 1.55 to 1.80 V and a Tafel slope of 65 mV/decade atoms and 1/8 by Mn4+ atoms, and by vacancies.29 The vacancies are
was achieved for NiO whereas 88 mV/decade for Ni6MnO8 ordered in the alternative (111) planes (Fig. 4a). Under oxidantꢀ
associated with a rate determining chemical step preceded by a driven and photochemical conditions, not only the Ni6MnO8
reversible electrochemical step at equilibrium (Fig. S27). Increase in provides more active sites due to the presence of higher number of
the apparent Tafel slope values were seen for MnNi2O4 and Ni2+ as active centres that are supported and stabilised by Mn4+ but
NiMn2O4 that could correspond to a change in the reaction also an additional (extra) hole density drives this reaction efficiently.
mechanism but would also be expected if mass or ion transport However, both MnNi2O4 and NiMn2O4 crystallise in cubic (space
limitations became significant.27,28 However, from the above group Fd3m) system and belong to the spinel type (AB2O4) structure
electrochemical behaviour, it can be inferred that a higher content of (Fig. 4b).30,31 The Mn4+ ions occupy the tetrahedral sites and the
Ni ions in the structure leads to lower Tafel slopes and thus, octahedral sites are preferred by Ni2+/3+ for MnNi2O4 whereas the
beneficial electroꢀcatalytical properties.
tetrahedral sites are occupied by Ni2+ and octahedral by Mn3+ for
NiMn2O4. It has been already well described that the octahedral sites
in a spinel structure play a prominent role than that of tetrahedral
sites for water oxidation making Ni2+/3+ higher active than Mn3+ and
that itself explains the higher activity of MnNi2O4 in comparison to
the NiMn2O4.32ꢀ34 The NiO (cubic Fm3m) adopts a rockꢀsalt
structure35 similar to Ni6MnO8 (Fig. 4c) with octahedral Ni2+ and O2ꢀ
and perhaps because of unavailable support of manganese, displays
limited activity.
The situation is partly reversed in the electrochemical water
oxidation. The NiO exhibits highest activity followed by nickel
manganese oxides. This is due to a large amount of amorphous
NiOOH, where Ni3+ is hexaꢀ coordinated (Fig 4d),36 is formed on the
surface of the electrodes (as shown by TEM and XPS) under
electrochemical conditions and the resulting amorphous phase is
known to be active for water oxidation by making the system very
efficient and has been already well established for other nickel oxide
and hydroxides.16,23,25 Interestingly, for Ni6MnO8, MnNi2O4, and
NiMn2O4 lesser amount of NiOOH is generated depending on the
amount of nickel present in the catalysts. Therefore, it can be
Fig. 3. Cyclic voltammograms (sweep rate 20 mV/s) of nickel
manganese and nickel oxide thin film catalysts in 0.1 M KOH (pH
13).
Furthermore, to test the stability of all catalysts,
chronoamperometric experiments were carried out (Fig. S28) and the
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DOI: 10.1039/C4CC09671A
3. A. Singh and L. Spiccia, Coord. Chem. Rev. , 2013, 257, 2607ꢀ2622.
4. A Indra, P. W. Menezes,N. R. Sahraie, A. Bergmann, C. Das, M. Tallarida,
D. Schmeißer, P. Strasser and M. Driess, J. Am. Chem. Soc., 2014, 136,
17530ꢀ17536.
5. H. Dau, C. Limberg, T. Reier, M. Risch, S. Roggan and P. Strasser,
ChemCatChem, 2010, 2, 724ꢀ761.
6. A. Iyer, J. DelꢀPilar, C. K. King'ondu, E. Kissel, H. F. Garces, H. Huang,
A. M. ElꢀSawy, P. K. Dutta and S. L. Suib, J. Phys. Chem. C, 2012, 116,
6474ꢀ6483.
concluded that for oxidantꢀdriven and photoꢀcatalytic water
oxidation Ni6MnO8 is efficient due to the higher amount of Ni active
sites stabilised by manganese and higher structuralꢀhole density
whereas amorphous NiOOH seems to be crucial for electroꢀcatalytic
water oxidation due to its structural features.
7. M. M. Najafpour, T. Ehrenberg, M. Wiechen and P. Kurz, Angew. Chem.
Int. Ed., 2010, 49, 2233ꢀ2237.
8. M. M. Najafpour, F. Rahimi, M. Amini, S. Nayeri and M. Bagherzadeh,
Dalton Trans., 2012, 41, 11026ꢀ11031.
9. F. Jiao and H. Frei, Chem. Commun., 2012, 46, 2920ꢀ2922.
10. F. Jiao and H. Frei, Energy Environ. Sci., 2012, 3, 1018ꢀ1027.
11. Y. Meng, W. Song, H. Huang, Z. Ren, S.ꢀY. Chen and S. L. Suib, J. Am.
Chem. Soc., 2014, 136, 11452ꢀ11464.
12. A. Indra, P. W. Menezes, I. Zaharieva, E. Baktash, J. Pfrommer, M.
Schwarze, H. Dau and M. Driess, Angew. Chem. Int. Ed., 2013, 52,
13206ꢀ13210.
13. P. W. Menezes, A. Indra, P. Littlewood, M. Schwarze, C. Goebel, R.
Schomaecker and M. Driess, ChemSusChem, 2014, 7, 2202ꢀ2211.
14. R. D. L. Smith, M. S. Prevot, R. D. Fagan, Z. Zhang, P. A. Sedach, M. K.
J. Siu, S. Trudel and C. P. Berlinguette, Science, 2013, 340, 60ꢀ63.
15. Y. Yang, H. Fei, G. Ruan, C. Xiang and J. M. Tour, ACS Nano, 2014, 8,
9518ꢀ9523.
16. K. Fominykh, J. M. Feckl, J. Sicklinger, M. Doeblinger, S. Boecklein, J.
Ziegler, L. Peter, J. Rathousky, E.ꢀW. Scheidt, T. Bein and D.
FattakhovaꢀRohlfing, Adv. Funct. Mater., 2014, 24, 3123ꢀ3129.
17. J. Suntivich, K. J. May, H. A. Gasteiger, J. B. Goodenough and Y. Shaoꢀ
Horn, Science, 2012, 334, 1383ꢀ1385.
18. E. L. Miller and R. E. Rocheleau, J. Electrochem. Soc., 1997, 144, 1995ꢀ
2003.
19. P. W. Menezes, A. Indra, R. N. Saharie, A. Bergmann, P. Strasser and M.
Driess, ChemSusChem, 2015, 8, 164ꢀ171.
20. D. Hong, Y. Yamada, A. Nomura and S. Fukuzumi, Phys. Chem. Chem.
Phys., 2013, 15, 19125ꢀ19128.
21. M. Elbaydi, S. K. Tiwari, R. N. Singh, J. L. Rehspringer, P. Chartier, J. F.
Koenig and G. Poillerat, J. Solid State Chem., 1995, 116, 157ꢀ169.
22. H. W. Nesbitt and D. Banerjee, Am. Mineral., 1998, 83, 305ꢀ315.
23. M. Gao, W. Sheng, Z. Zhuang, Q. Fang, S. Gu, J. Jiang and Y. Yan, J.
Am. Chem. Soc., 2014, 136, 7077ꢀ7084.
24. M. E. G. Lyons and M. P. Brandon, Int. J. Electrochem. Sci., 2008, 3,
1386ꢀ1424.
25. L. Trotochaud, J. K. Ranney, K. N. Williams and S. W. Boettcher, J. Am.
Chem. Soc., 2012, 134, 17253ꢀ17261.
Fig. 4. Structural units of (a) Ni6MnO8, (b) MnNi2O4, (c) NiMn2O4
and (d) NiO (see text for details). Atom codes, blue: Mn4+ or Ni2+;
green: Ni2+, Ni3+/2+ or Mn3+; red: O2ꢀ; gray: H+, yellow: vacancy
In conclusion, we investigated for the first time, the oxidantꢀ
driven, photochemical and electrochemical water oxidation
employing nickel manganese oxideꢀbased catalysts (Ni6MnO8,
MnNi2O4, NiMn2O4) with various Ni:Mn ratios and
morphologies, starting from wellꢀdefined heterobimetallic
nickel manganese SSPs; their activities were compared with
NiO. Nickelꢀrich manganese oxides were found to be highly
efficient with very high activity for oxidantꢀdriven and photoꢀ
catalytic water oxidation whereas NiO exhibited higher
performance and remarkable stability for electroꢀcatalytic water
oxidation. Based on the crystallographic aspects, a structureꢀ
activity relationship could be deduced from structural features
of the oxide systems. The latter relationship deduced here can
help to predesign new material to boost efficiency of water
oxidation.
26. C. C. L. McCrory, S. Jung, J. C. Peters and T. F. Jaramillo, J. Am. Chem.
Soc., 2013, 135, 16977ꢀ16987.
Financial support by the BMBF (L2H project) and the DFG (Cluster
of Excellence UniCat) is gratefully acknowledged. O. Levy would
like to thank Einstein Foundation Berlin for the financial support and
Prof. David Avnir for the helpful discussions.
27. Y. Surendranath, M. W. Kanan and D. G. Nocera, J. Am. Chem. Soc. ,
2010, 132, 16501ꢀ16509.
28. S. W. Lee, C. Carlton, M. Risch, Y. Surendranath, S. Chen, S. Furutsuki,
A. Yamada, D. G. Nocera and Y. ShaoꢀHorn, J. Am. Chem. Soc., 2012,
134, 16959ꢀ16962.
29. P. Porta, G. Minelli, I. L. Botto and E. J. Baran, J. Solid State Chem.,
1991, 92, 202ꢀ207.
30. A. B. Devale and D. K. Kulkarni, J. Phys. C, 1982, 15, 899ꢀ905.
31. S. Asbrink, A. Waskowska, M. Drozd and E. Talik, J. Phys. Chem.
Solids, 1997, 58, 725ꢀ729.
32. T. W. Kim, M. A. Woo, M. Regis and K.ꢀS. Choi, J. Phys. Chem Lett.,
2014, 5, 2370ꢀ2374.
33. E. Rios, P. Chartier and J. L. Gautier, Solid State Sci., 1999, 1, 267ꢀ277.
34. Y. Liang, H. Wang, J. Zhou, Y. Li, J. Wang, T. Regier and H. Dai, J. Am.
Chem. Soc., 2011, 134, 3517ꢀ3523.
Notes and references
a
Metalorganic Chemistry and Inorganic Materials, Department of
Chemistry, Technische Universität Berlin, Strasse des 17 Juni 135, Sekr.
C2, Dꢀ10623 Berlin, Germany *Email: matthias.driess@tuꢀberlin.de
b
The Harvey M. Krueger Family Center for Nanoscience and
Nanotechnology, The Hebrew University of Jerusalem, Edmond J. Safra
Campus, Givat Ram, Jerusalem, 91904, Israel
Electronic Supplementary Information (ESI) available: Complete
experimental details and characterisation of precursors and oxides before and
after oxidantꢀdriven, photoꢀcatalytic and electroꢀcatalytic water oxidation.
See DOI: 10.1039/c000000x/
1. J. Luo, J.ꢀH. Im, M. T. Mayer, M. Schreier, M. K. Nazeeruddin, N.ꢀG.
Park, S. D. Tilley, H. J. Fan and M. Gratzel, Science, 2014, 345, 1593ꢀ
1596.
35. S. Sasaki, K. Fujino and Y. Takeuchi, Proc. Jpn. Acad., Ser. B, 1979, 55,
43ꢀ48.
36. M. CasasꢀCabanas, J. CanalesꢀVazquez, J. RodriguezꢀCarvajal and M. R.
Palacin, Solid State Ionics 2009, 131ꢀ136.
2. M. W. Kanan and D. G. Nocera, Science, 2008, 321, 1072ꢀ1075.
4 | J. Name., 2014, 00, 1-3
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