Synergistical photo-thermal-catalysis of Zn2GeO4:xFe3+ for H2 evolution in NaBH4 hydrolysis reaction

Article abstract of DOI:10.1016/j.catcom.2021.106321

Herein, we reported the systematic investigation of synergistic photo-thermal-catalysis for NaBH₄ hydrolysis reaction based on zinc orthogermanate. A series of Zn₂GeO₄:xFe³⁺ (x = 0 to 0.10) catalysts were prepared via solvothermal method. The H₂ evolution experiments demonstrated that the photogenerated holes trap OH^? not only shifted the equilibrium of NaBH₄ hydrolysis reaction toward the direction of H₂ evolution, but also inhibited the recombination of photogenerated carriers. With the remarkable photo-thermal synergism for the as-prepared catalysts, the H₂ evolution rate in photo-thermal-driven condition had witnessed several times higher than that in mono-energy driven condition. The catalysts remained stable after circulation tests.

Full text of DOI:10.1016/j.catcom.2021.106321

Catalysis Communications 156 (2021) 106321
Contents lists available at ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short communication
3
+
Synergistical photo-thermal-catalysis of Zn GeO :xFe for H evolution in
2
4
2
NaBH hydrolysis reaction
4
a,
*
a
a
a,
b
a
a,*
Qiaoqi Li , Fei Wang , Xin Zhou , Jianmei Chen , Chao Tang , Lili Zhang
a
School of Chemistry and Chemical Engineering, Huaiyin Normal University, Jiangsu Key Lab for Chemistry of Low-Dimensional Materials, No.111 West Changjiang
Road, Huai'an 223300, Jiangsu Province, PR China
b
College of Chemistry and Chemical Engineering, Changzhou University, Gehu Road 1, Changzhou, Jiangsu 213164, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
Herein, we reported the systematic investigation of synergistic photo-thermal-catalysis for NaBH hydrolysis
4
Zn
2
GeO
4
3+
reaction based on zinc orthogermanate. A series of Zn
solvothermal method. The H
only shifted the equilibrium of NaBH
the recombination of photogenerated carriers. With the remarkable photo-thermal synergism for the as-prepared
catalysts, the H evolution rate in photo-thermal-driven condition had witnessed several times higher than that in
mono-energy driven condition. The catalysts remained stable after circulation tests.
2
GeO
4
:xFe (x = 0 to 0.10) catalysts were prepared via
NaBH
4
hydrolysis reaction
ꢀ
2
evolution experiments demonstrated that the photogenerated holes trap OH not
Hydrogen evolution
Photo-thermal-catalysis
Synergism
4
2
hydrolysis reaction toward the direction of H evolution, but also inhibited
2
1
. Introduction
recent decades, various of efficient catalysts have been developed for
achieving rapid H evolution from NaBH
hydrolysis reaction [7–10].
The first-generation catalysts were traditional noble metal-based mate-
rials, including platinum [11], silver [12], palladium [13], gold [14],
rhodium [15] and ruthenium [16]. Later on, next-generation catalysts
were based on the non-noble transition metal, such as ferrum [17], co-
balt [18], nickel [19] and copper [20]. The catalysts exhibited excellent
2
4
Hydrogen, a fantastic clean energy carrier with high energy density
8
ꢀ 1
(
1.42 × 10 J⋅Kg ) is the viable alternative energy source of fossil fuels
1]. Currently, the solutions of hydrogen storage are achieved by gas
compression and gas liquefaction. For the low density of hydrogen gas
[
ꢀ 1
(
0.0899 g⋅L ), storing compressed hydrogen requires high pressure and
huge storage capacity vessel [2]. Moreover, as the low boiling point of
hydrogen (20.37 K), the liquefaction and storage processes consume
massive energy to maintain the low temperature environment [3]. The
hydrogen storage techniques mentioned above not only uneconomic,
but also with potential safety hazard in the processes of production,
transportation and application. However, chemical hydrides could
perfectly solve the challenges above and have been regarded as the ideal
hydrogen storage medium [4].
catalytic capacity for H
2
evolution in NaBH
4
hydrolysis reaction.
ꢀ
Notably, the content of OH in the solution system was remarkable
increased with the catalytic reaction proceeded. As a result, resulting
high pH-value inhibited the hydrolysis of NaBH
4
solution and decreased
hydro-
the H evolution rate [21]. The mainstream research on NaBH
2
4
lysis reaction was traditional chemical catalysis driven by thermal ra-
diation. Unlike the mechanism of traditional chemical catalysis,
ꢀ
+
photocatalytic reactions based on the electron and hole pairs (e /h
Compared with other chemical hydrides, NaBH
4
is an effective and
pairs) generated by irradiation. Over the past several years new ideas
have surged in adoption and brought about improved ways to enhance
the hydrogen evolution via photocatalytic reactions [22–24]. Here, the
safe solid-state hydrogen resource medium with the following advan-
tages, such as non-toxic, non-combustible, non-explosive and high
hydrogen storage capacity [5]. Four moles of hydrogen can be obtained
ꢀ
photogenerated holes could effectively consume the excess OH ions,
from hydrolyzing every mole of NaBH
4
by the following equation [6].
which transfer the NaBH
4
hydrolysis reaction equilibrium to the direc-
ꢀ
)
tion of H evolution. In addition, the recombination of photogenerated
2
1
NaBH
4
+ 2H
2
O→NaBO
2
+ 4H
2
↑ ΔH = ꢀ 217 kJ⋅m olꢀ
ꢀ
+
e /h pairs could effectively prevent by the consumption of photo-
generated holes. Combined with the two factors above, hydrogen could
As the reaction product (NaBO
2
) can be converted back to NaBH
4
, it
4
be generated rapidly from NaBH hydrolysis reaction by synergistically
is easy to accomplish a closed-loop hydrogen energy system. During the
*
Corresponding authors.
E-mail addresses: lqq@hytc.edu.cn (Q. Li), zll@hytc.edu.cn (L. Zhang).
https://doi.org/10.1016/j.catcom.2021.106321
Received 21 March 2021; Received in revised form 18 April 2021; Accepted 1 May 2021
Available online 3 May 2021
1
566-7367/© 2021 The Author(s).
Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
(
http://creativecommons.org/licenses/by-nc-nd/4.0/).

Q. Li et al.
Catalysis Communications 156 (2021) 106321
photo-thermal-catalytic effect.
with GC-TCD (the carrier gas was N
was performed to detect the evolution amount of hydrogen. In a typical
test, the as-prepared catalyst (20 mg), NaOH (1000 mg) and NaBH
4
2
) and a 5A molecular sieve column
Here, the work was concerned with applying photocatalyst to NaBH
4
hydrolysis reaction. Zn
for the potential material as the high chemical stability. Moreover, the
electronic configuration of Zn GeO allowed excellent mobility for the
photogenerated electron-hole pairs [25]. A series of Zn
0 to 0.10) solid-solutions were obtain via a simple solvothermal
2
GeO
4
, an excellent photocatalyst was selected
(300 mg) were added into a three-neck Pyrex quartz glass vessel (150
mL). The reaction system kept vacuum for 20 min. Then, de-gased
deionized (20 mL) water was injected into the glass vessel through the
rubber plug by an injector. All the feed reactants were dispersed well by
magnetically stirring. The temperature of the reactor vessel was main-
2
4
:xFe3 (x
+
GeO
4
2
=
method. Compared with mono-energy driven condition, the H
2
evolu-
:xFe3 (x = 0 to 0.05) solid-solutions in photo-
+
tained at the range of 10 to 40 C by programmed-control system. UV-
◦
tion rate for Zn
2
GeO
4
thermal-driven condition could be improved for several times. It was
verified to certain that the synergistically photo-thermo-catalytic effect
light and visible-light irradiation were provided by CEL-M500 mer-
cury lamp (AuLight, 500 W) and CEL-LED100HA lamp (AuLight, 100
W), respectively.
of Zn
2
GeO
4
for H
2
evolution in NaBH
4
hydrolysis reaction. As the
representative samples, Zn
2
GeO afforded the H
4
2
evolution rate of 5.45
ꢀ 1
ꢀ 1
◦
mmol⋅h ⋅g
under UV-light irradiation at 40 C. Besides,
3. Result and discussion
:0.05Fe3 exhibited the H
+
evolution rate of 2.93 mmol⋅h ⋅g
ꢀ 1 ꢀ 1
Zn
2
GeO
4
2
◦
at 40 C under visible-light irradiation. This work demonstrated that
3.1. Characterization of catalysts
NaBH
4
hydrolysis reaction could be catalyzed via photocatalyst by the
synergistical photo-thermal-catalysis.
The XRD patterns of the as-obtained samples confirmed Zn GeO :
2
4
xFe3 (x = 0 to 0.1) samples with fine crystallinity via solvothermal
+
2
. Experimental
preparation method (See Fig. 1). The diffraction peaks of bare-Zn GeO
2
4
and low Fe3 doped Zn
+
GeO
(x = 0.01 to 0.05) samples were almost the
2
4
2
.1. Materials
same without any signal of impurity phase. However, it was quite
obvious that there existed an impurity phase peak in the pattern of 10
atom% Fe3 -doped Zn GeO . Zn GeO is composed of two different
+
The reagents in this work were commercial reagents which without
2
4
2
4
further purification. Zn(CH
O were commercial analytical pure grade (99.9%, Aladdin Chemical
Reagent Corp.). GeO was commercial high purity grade (99.999%,
3
COO)
2
, Fe(NO
3
)
3
⋅9H
2
O, NaBH
4
, NaOH and
tetrahedra (ZnO4 and GeO ) which bridged by O atoms with the space
4
D
2
group of R-3 (See the inset of Fig. 1). According to the data of ionic
3
+
2+
2
radius, the effective ionic radius of Fe ion (0.49 Å) is smaller than Zn
ion (0.60 Å), but larger than Ge4 ion (0.39 Å) in four-coordinated
+
Shanghai Macklin Biochemical Co., Ltd). Ethylenediamine was com-
mercial analytical pure grade (99.5%, Sinopharm Chemical Reagent
3
+
environment [26]. For the balance of electric charges, Fe ion have
to replace both Ge4 ion and Zn ion sites respectively, forming dis-
+
2+
2
Corp.). Nitrogen (N ), helium (He) were high pure grade (6 N, Yuanneng
Biotechnology Co., Ltd.).
torted molecular framework geometry. Therefore, the molecular
framework of Zn
2
GeO
4
could not tolerate a higher doping content of
3
+
3+
2
.2. Preparation of photocatalysts
Fe ion. The crystal parameters of Zn GeO :xFe (x = 0 to 0.05)
2
4
samples were estimated by Rietveld refinement method and the minor
error factors indicated reliable results (See Table S1 in the Supplemen-
tary material). It should be noticed that the value of a, c and V were
:xFe3 (x = 0 to 0.10) catalysts were obtained by sol-
+
Zn
2
GeO
4
vothermal method. In
CH COO)
a typical synthesized, stoichiometric Zn
3
+
(
3
2
(1 mmol), GeO
2
and Fe(NO
3
)
3
⋅9H
2
O were mixed with
expanded with doping concentration of Fe ion, confirming the effec-
+
tive doping of Fe3 ion into the Zn GeO framework.
2 4
deionized water (3 mL) and ethylenediamine (6 mL) into a stainless
autoclave. The aggregate amounts of Ge4 ion and Fe ion cations were
+
3+
3+
The morphologies of the as-obtained Zn GeO :xFe solid-solutions
2
4
◦
0
.5 mmol. The mixture was stirring for one hour at 80 C to form a
(x = 0 to 0.05) were observed via SEM measurements. Fig. 2 displayed
homogeneous viscous colloid. Subsequently, the autoclave maintained
that all the products exhibited flower-like morphology composed of
◦
at 180 C for 10 h. Ultimately, the as-obtained precipitate was washed
nanobelts with 3–4
μ
m in length and several nanometers in width. The
for several time with warm deionized water. The desired product was
high resolution TEM images (See Fig. 3) presented distinct morphologies
◦
3+
obtained after drying at 80 C for several hours.
of Zn GeO and Zn GeO :0.05Fe , which confirmed the Zn GeO :
2
+
4
2
4
2
4
3
xFe nanobelts with about 20 nm in width. Raul [27] et al. reported
2
.3. Characterization devices
that the pH-value and GeO content in the initial solution were relevant
2
to the morphologies of Zn
2 4
GeO . This work was not concerned about the
3
+
Powder X-ray diffraction (XRD) data were obtained by a Philips
morphology control of Zn GeO . As a typical sample, Zn GeO :0.05Fe
2
4
2
4
PANanlytical X'Pert XRD system (Cu Ka radiation, 45 kV, 40 mA, λ =
.5418 Å). The morphologies of as-prepared catalyst were carried out by
was chosen for EDS analysis and element mapping investigation. The
images demonstrated the atoms of Zn, Fe, Ge and O were homogeneous
1
3
+
FEI Quanta 450FEG field emission scanning electron microscope system
and JEM-2100F field emission transmission electron microscope system.
The specific surface area was determined by using BET method on a
distributed on the surface of Zn GeO :0.05Fe (See Fig. 2).
2 4
3
+
The specific surface areas of the obtained Zn GeO :xFe (x = 0 to
2
4
0.05) samples were measured by BET nitrogen absorption method. The
BET plots (Fig. S1) demonstrated that the catalysts obtained via sol-
Quantachrome Quadrasorb SI N
2
adsorption-desorption analyzer at 77
◦
2
ꢀ 1
K. All the as-synthesized materials were degassed at 280 C for 2 days.
UV–Visible diffuse reflectance spectra (DRS) were measured by a Shi-
madzu UV-3600 UV–Vis-NIR spectrometer (λ = 200–800 nm) equipped
with an integrating sphere. The background noise of the spectrometer
vothermal method exhibited minor specific surface areas (2–3 m ⋅g ).
The results were consistent with the observations from FESEM analyses.
To determine the chemical valence state of the ions in the as-
obtained samples, X-ray photoelectron spectroscopy (XPS) was carried
3
+
3+
was corrected by BaSO
4
. Axis Ultra Imaging XPS Spectrometer was
out on Zn GeO :0.01Fe as the representative of Zn GeO :xFe (x =
2
4
2
4
employed to obtain X-ray photoelectron spectroscopy spectrum.
0 to 0.05) samples (See Fig. 4). The high-resolution XPS revealed the
characteristic binding energy peaks of Zn, Ge and Fe ions from the test
sample (See the inset of Fig. 4). The characteristic peaks located at
2
.4. Catalytic hydrogen evolution tests
4
+
1
221.2 eV and 1252.4 eV were belonged to the orbits for Ge ion (Ge
The catalytic hydrogen evolution tests were performed in an evac-
2p1/2 and Ge 2p3/2, respectively) [28]. Besides, the characteristic peaks
of Zn2 ions which located at 1045.6 eV (Zn 2p1/2) and 1022.5 eV (Zn
+
uation AuLight CEL-PAEM-D8 photo-thermal characterization system.
An online automatic Shimadzu GC-8A gas chromatograph equipped
2p3/2), respectively [28]. In the right inset of Fig. 2, the two weak peaks
2

Q. Li et al.
Catalysis Communications 156 (2021) 106321
3
+
3+
Fig. 1. The X-ray diffraction patterns of as-obtained Zn
2
GeO
4
:xFe catalysts (x = 0 to 0.10). The impurity phase peak observed in the pattern of Zn
2
GeO
4
:0.10Fe
.
3
+
(
inset) The projection image of Zn
2
GeO
4
:xFe exhibited through the [111] direction. Color code: cyan tetrahedra, ZnO
4
; green tetrahedra, GeO
4
; Cyan, green, red
spheres represented Zn, Ge and O atoms, respectively.
+
appeared at 725.6 eV and 711.7 eV were corresponding to the orbits for
Ge4 ions ensured the light harvest in the UV-light spectrum, the H
2
3
+
3+
Fe ion (Fe 2p1/2 and Fe 2p3/2, respectively) [28]. Although the in-
evolution rate for Zn
2
GeO
4
:xFe (x = 0.01 to 0.05) solid-solutions
3
+
3+
2+
4+
tensity of Fe 2p peaks were rather weak as the low concentration of Fe
decreased with the progresses of Fe to Zn /Ge substitution. It
ions, it still confirmed the effective doping of Fe3 ion into the Zn
+
GeO
should be noted that the H
evolution rate for Zn
:xFe (x = 0.01
3+
2
4
2
2
GeO
4
framework.
to 0.05) solid-solutions under visible light irradiation was greatly
3
+
The diffuse reflectance spectra in Fig. 5 revealed that the light
increased with the doping content of Fe ions increasing. There was no
+
3+
adsorption of the Zn
2
GeO
4
:xFe3 (x = 0 to 0.05) samples in the visible
doubt that Fe ion improved the optical absorbance in the visible light
3
+
light region were remarkably enhanced with the Fe ion doping into
region, which consistent with the observation in the DRS spectrum (See
3
+
the framework of Zn
2
GeO
4
. Meanwhile, with the increasing concentra-
Fig. 5). Therefore, Zn
capacity (H
2 4
GeO :0.05Fe exhibited the maximum catalytic
tion of Fe3 , the spectra for Zn
+
3+
: 2.93 mmol⋅h ⋅g ) at 40 C under visible light irradia-
ꢀ 1 ꢀ 1
◦
2
4
GeO :xFe (x = 0 to 0.05) samples
2
shifted toward the direction of long wave. The band gap energy of the
tion. The results of the tests substantiated the synergistical photo-
Zn
2
GeO
4
:xFe3 (x = 0.01 to 0.05) samples were calculated to be 3.81 eV
+
thermal-catalytic effect for Zn
reaction.
2
GeO
4
:xFe
3+
4
in NaBH hydrolysis
n/2
to 3.40 eV from the Taus plots with the formula
α
hv = A(hv-E
g
)
, in
is
the absorption coefficient related to hv, and A is a constant [29]. The E
which E
g
is the band gap energy, hv is the incident photon energy,
α
g
3
.3. Mechanism discussion
+
of the Zn
ZnGa
2
GeO
(4.52 eV) (See the inset of Fig. 5).
4
:xFe3 catalysts were much narrow than that of bare-
2
O
4
The photo-thermal-catalytic NaBH
hydrolyzation was the combi-
4
hydrolytic reaction and photocatalytic water splitting
4
nation of NaBH
3
.2. Catalytic performance
The investigations of catalytic H
reaction. A set of reference experiments based on deuterium labeling
method (H O in the reaction system was displaced by D O) were per-
2
2
2
evolution performance were car-
formed to verify the possible mechanism of the synergistically photo-
ried out in three types of energy-driven conditions for each catalyst, such
as thermal-driven, photo-driven and photo-thermal-driven. A mercury
thermal-catalytic effect. The experiments were catalyzed by bare-
◦
Zn
2
GeO
4
(20 mg) under UV-light irradiation at 40 C for two hours. Na
2
-
UV-light lamp was provided for bare-Zn
2
GeO
4
. Meanwhile, the LED
EDTA (10 mg), a conventional scavenger of photogenerated holes was
added into the reference group A. Besides, the reference group B without
:xFe3 (x = 0.01 to 0.05)
+
visible-light lamp was provided for Zn GeO
2
4
solid-solutions. According to the Arrhenius formula ln k = ln A – E
a
/RT,
2
Na -EDTA was treated as the control group. The composition analyses of
there exists an apparent positive linear correlation between the H
2
the gaseous products were carried out by an online cryogenic gas
chromatograph equipped with GC-TCD. The carrier gas was helium and
operated at 77 K. Generally, the reactant with deuterium requires much
higher apparent activation energy than the isostructural compounds
evolution rate and thermodynamic temperature. However, excessively
high temperature is not suitable for practical hydrogen-energy appli-
cation. Therefore, the temperature of thermal-driven and photo-
◦
thermal-driven condition were all 40 C. The H
2
evolution rate for the
with protium [30]. Therefore, the NaBH
released H . Meanwhile, the photocatalytic water splitting reaction
released only D . The fingerprint peaks from gas chromatograph
demonstrated that after the addition of Na -EDTA the proportions of
protium (H ) and deuterium (D ) were decreased and increased,
respectively (see Fig. S2). The reference experiments indicated that the
consumption of photogenerated holes inhibited both NaBH hydrolytic
4
hydrolytic reaction mainly
as-prepared catalysts exhibited in Table 1. It was certainly manifested
that the H evolution rates for all the samples in photo-thermal-driven
2
2
2
condition were several times than that in mono-energy-driven condi-
2
+
tion. Compared with Zn
Zn GeO
2
GeO
4
:xFe3 (x = 0.01 to 0.05) solid-solutions,
2
2
2
4
exhibited the highest catalytic performance for H
2
evolution
2+
ꢀ 1
ꢀ 1
◦
(
5.45 mmol⋅h ⋅g ) at 40 C under UV-light irradiation. As Zn and
4
3

Q. Li et al.
Catalysis Communications 156 (2021) 106321
3
+
3+
3+
Fig. 2. FESEM images of Zn
2
4 2
GeO , Zn GeO
4
:0.01Fe , Zn
2
GeO
4
:0.02Fe and Zn
2
GeO
4
:0.05Fe . SEM elemental mapping for Zn, Fe, Ge and O, the scale bars were
1 μm.
reaction and enhanced photocatalytic water splitting reaction. Conse-
quently, the photogenerated holes served as a crucial role in the syn-
ergistically photo-thermal-catalytic effect. The process of the excess
obtained by Arrhenius formula ln k = ln A – E
a
/RT, in which A is a
constant, k is the H evolution rate, R is the universal molar gas constant
2
and T is the thermodynamic temperature. The E
a
values of bare-
ꢀ
ꢀ 1
3+
ꢀ 1
OH ions consumed by photogenerated holes could not only effectively
Zn
2
GeO
4
(29.6 KJ⋅mol ) and Zn
2
GeO
4
: 0.05Fe (33.7 KJ⋅mol ) for
enhanced the NaBH
bination of photogenerated e /h pairs, leading much higher H
duction for photocatalytic H
factors above, hydrogen could be generated rapidly from NaBH
4
hydrolysis reaction, but also inhibited the recom-
NaBH
4
hydrolytic reaction were calculated by the slop of the straight
ꢀ
+
2
pro-
hy-
line on Arrhenius plot (lnk) versus temperature factor (1/T) for each
catalyst (See Fig. S3b). Obviously, a lower apparent activation energy
for a catalyst means a better catalytic performance.
2
evolution process. Combined with the two
4
drolysis reaction under photo-thermal-driven condition. The probable
reaction mechanism presented in the Graphic Abstract.
3
.5. Stability tests
3
.4. The kinetics studies of NaBH
4
hydrolytic reactions
The structure and catalytic performance of catalysts should be stable
and reliable in hot alkaline solution and irradiated with strong ultravi-
For the kinetics study of the NaBH
activation energy (E ) is a major factor to evaluate the performance of
catalyst. The studies were carried out under UV-light (bare-Zn GeO
: 0.05Fe3 ), respectively. The
hydrogen evolution rates increased significantly with temperature rising
4
hydrolytic reaction, the apparent
olet radiation. Zn
2
GeO
4
(200 mg) as the catalyst for NaBH
4
hydrolytic
◦
a
reaction at 40 C under ultraviolet irradiation for 10 h. After the reac-
tion, the catalyst was recycled into the next round of testing with freshly
prepared solution. The hydrogen evolution rate has witnessed slight
downward trend in the inset of Fig. 6 due to the loss of catalyst in the
recycled processes. At the end of the cycling tests, the powder XRD
2
4
)
+
2 4
and visible light irradiation (Zn GeO
◦
◦
from 10 C to 40 C. (See Fig. S3a). The apparent activation energy is
4

Q. Li et al.
Catalysis Communications 156 (2021) 106321
3
+
.
Fig. 3. TEM and HRTEM images of Zn
2
GeO
4
and Zn
2
GeO
4
:0.05Fe
3
2 4 2 4
+
3+
Fig. 4. The full survey X ray photoelectron spectroscopy spectra of Zn GeO :0.01Fe . (inset) The high-resolution XPS spectra of each element in Zn GeO :0.01Fe
(
Ge 2p state, Zn-2p state and Fe-2p state).
pattern of Zn
without any impurity phase (see Fig. 6). Consequently, Zn
maintain its structure and provided reliable catalytic performance in
harsh photo-thermal-driven condition for NaBH hydrolytic reaction.
2
GeO
4
remained the same as the as-prepared sample
4. Conclusions
2
GeO could
4
:xFe3 (x = 0 to 0.05) samples were
+
2 4
In the present work, Zn GeO
4
successfully synthesized via a simple solvothermal method. The as-
2 4
obtained photocatalysts were applying to H evolution from NaBH
hydrolysis reaction. The process of the excess OH- ions consumed by
5

Q. Li et al.
Catalysis Communications 156 (2021) 106321
3
+
3+
Fig. 5. Diffuse reflectance spectra for Zn
2
GeO
4
:xFe (x = 0 to 0.05) samples. (inset) Tauc plot for Zn
2
GeO
4
:xFe (x = 0 to 0.05) samples.
2
remarkable photo-thermal synergism, the H evolution rate in photo-
Table 1
thermal-driven condition was several times higher than that in mono-
energy driven condition. This work demonstrated that the conven-
2 4 2 4
The H evolution kinetics of NaBH hydrolysis reaction catalyzed via Zn GeO :
3
+
xFe (x = 0 to 0.05) in the various types of energy-driven conditions.
tional photocatalyst could be used as the highly efficient H
2
evolution
◦
◦
◦
◦
◦
4
0
C in
10 C &
40 C &
10 C &
40 C &
visible
light
catalyst for NaBH hydrolysis reaction via the synergistically photo-
4
dark
UV-light
UV-light
visible
light
thermal-catalytic effect.
Zn
2
Zn
2
Zn
2
Zn
2
GeO
GeO
GeO
GeO
4
4
4
4
119.33
125.15
131.20
141.58
442.56
423.28
408.37
392.56
5447.55
4883.34
4644.28
4245.19
–
–
3
3
3
+
+
+
Declaration of Competing Interest
:0.01Fe
:0.02Fe
:0.05Fe
61.59
130.44
254.78
400.75
1419.71
2927.99
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Acknowledgements
This work was supported by National Natural Science Foundation of
China (Grants number 21808076); Natural Science Foundation of
Jiangsu Province, China (Grants number BK20181069); Natural Science
Foundation of the Jiangsu Higher Education Institutions of China
(
(
20KJB430050); Huai'an Municipal Science and Technology Bureau
HAB201907).
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.catcom.2021.106321.
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