Catalytic performance of a square planar nickel complex for electrochemical‐ and photochemical‐driven hydrogen evolution from water

Article abstract of DOI:10.1016/j.inoche.2021.108780

A square planar nickel complex bearing salicylketoxime (SAO), Ni-SAO has been synthesized and well characterized by ESI-MS and single-crystal X-ray diffraction, etc. Ni-SAO exhibits good activity in both electrocatalytic and photocatalytic hydrogen evolution reaction (HER). Under an overpotential (OP) of 837.6 mV, Ni-SAO can electrocatalyze hydrogen evolution from a neutral aqueous buffer with a turnover frequency (TOF) of 1428 mol of hydrogen per mole of catalyst per hour (mol H₂ /mol catalyst/h). Moreover, under blue light (λ = 469 nm), a three-component system containing Ni-SAO as a catalyst, CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H₂A) as a sacrificial electron donor also can afford hydrogen with a turnover number (TON) of 8138 mol H₂ per mol of catalyst (mol of cat^?1) during 48 h irradiation. The highest apparent quantum yield (AQY) is about 16.5% at 469 nm.

Full text of DOI:10.1016/j.inoche.2021.108780

Inorganic Chemistry Communications 131 (2021) 108780
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Catalytic performance of a square planar nickel complex for
electrochemical- and photochemical-driven hydrogen evolution from water
*
Chun-Li Wang, Hao Yang, Juan Du, Shu-Zhong Zhan
College of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China
A R T I C L E I N F O
A B S T R A C T
Keywords:
A square planar nickel complex bearing salicylketoxime (SAO), Ni-SAO has been synthesized and well charac-
terized by ESI-MS and single-crystal X-ray diffraction, etc. Ni-SAO exhibits good activity in both electrocatalytic
and photocatalytic hydrogen evolution reaction (HER). Under an overpotential (OP) of 837.6 mV, Ni-SAO can
electrocatalyze hydrogen evolution from a neutral aqueous buffer with a turnover frequency (TOF) of 1428 mol
Nickel complex
Crystal structure
Electro and photocatalytic activity for HER
of hydrogen per mole of catalyst per hour (mol H
three-component system containing Ni-SAO as a catalyst, CdS nanorods (CdS NRs) as a photosensitizer, and
ascorbic acid (H A) as a sacrificial electron donor also can afford hydrogen with a turnover number (TON) of
138 mol H
per mol of catalyst (mol of cat 1) during 48 h irradiation. The highest apparent quantum yield
AQY) is about 16.5% at 469 nm.
2
/mol catalyst/h). Moreover, under blue light (λ = 469 nm), a
2
ꢀ
8
2
(
1
. Introduction
complex, Ni-SAO that has a good activity for hydrogen evolution.
Herein, we present the synthesis, characterization and catalytic activ-
ities for electrochemical and photochemical driven hydrogen evolution
of Ni-SAO.
The global demand for cost-effective and user-friendly energy has
sparked considerable interest in carbon-free renewable energy resources
1-3]. Hydrogen, a promising fuel, based on the photoelectric and
photocatalytic H O splitting, will be at the vanguard of this revolution
4]. In nature, hydrogenases surviving in anaerobic organisms can be
[
2
2. Experimental
[
divided into [NiFe]and [FeFe] hydrogenases according to the different
metal active center, which can catalyze reduction of protons efficiently
2.1. Materials and experimental methods
[
5]. Considering that hydrogenases are assembled by organic species
Reagent-grade chemicals were commercially purchased and used
with metal active sites, researchers focus their works on the design and
study of molecular catalysts based on transition metal complexes for
HER, and several complexes containing iron [6], cobalt [7], copper [8,9]
and nickel [10,11] have been developed as catalysts for hydrogen gen-
eration. It is apparent that cobalt complexes with oxime can serve as
catalysts for electrochemical or photochemical driven hydrogen evolu-
tion [12-14]. However, phenolic oxime nickel complexes used for
electro- and photocatalytic hydrogen production have rarely been re-
ported, although the Robertson group reported magnetic and electronic
performances of several nickel complexes with phenolic oxime species
without further purification. Tetra-butylammonium perchlorate ([(n-
4 4
Bu) N]ClO ) was used after secondary recrystallization. CdS NRs were
synthesized with a simple solvothermal method [16]. According to the
reported method [17], salicylketoxime (SAOH) was obtained by the
reaction of hydroxylamine hydrochloride with 2-hydroxybenzaldehyde.
Electrochemical measurements were performed using a CHI-660E
electrochemical workstation. Cyclic voltammograms (CVs) were recor-
2
ded by using a single-compartment cell possessing a 0.00785 cm glassy
carbon electrode as a working electrode, Pt counter electrode and Ag/
3
AgNO as a reference electrode. Controlled potential electrolysis (CPE)
[
15]. Moreover, the complex with a square-planar coordination geom-
were carried out in a two-compartment cell possessing the glassy carbon
electrode as the working electrode, Pt auxiliary electrode, and Ag/
etry is always selected as a proper candidate for HER. To this end, a new
phenolic oxime, salicylketoxime (SAOH) was designed in our Lab. The
reaction of the ligand, SAOH and nickel salt affords a new nickel
AgNO
3
or Ag/AgCl reference electrode.
In a photocatalytic experiment, a tube containing 5 mL aqueous
*
Corresponding author.
E-mail address: shzhzhan@scut.edu.cn (S.-Z. Zhan).
https://doi.org/10.1016/j.inoche.2021.108780
Received 24 April 2021; Received in revised form 25 June 2021; Accepted 29 June 2021
Available online 5 July 2021
1
387-7003/© 2021 Elsevier B.V. All rights reserved.

C.-L. Wang et al.
Inorganic Chemistry Communications 131 (2021) 108780
1
4 h, the precipitate was formed. The product was collected by filtration,
washed with ethanol, and dried in vacuo (0.15 g, 45% yield). Single
crystals suitable for X-ray analysis were obtained by slow evaporation of
12 2 4
an acetonitrile solution of Ni-SAO. Calc for C14H N NiO : C 50.76, H
3
.62, N 8.5. Found: C 50.2, H 3.40, N 8.9.
2
.3. Crystallographic structure determinations
The X-ray crystallographic data collections were carried out on a
Bruker Smart Apex II DUO area detector using graphite monochromated
Mo-K
α
radiation (λ = 0.71073 Å) at room temperature. The structure
was solved by SHElXT [20] in the OLEX2 crystallographic software
2
package [21] and refined by full-matrix least squares on F using
SHElXL-2018 [22]. All non-hydrogen atoms were refined anisotropi-
cally, and hydrogen atoms were treated as idealized contributions and
refined isotropically. A summary of crystallographic data for Ni-SAO
was given in Table S1.
Scheme 1. Synthesis of the ligand, SAOH and the nickel complex, Ni-SAO.
Fig. 1. (a) X-ray crystal structure of the nickel complex, Ni-SAO. (b) 2D layered
diagram of Ni-SAO along ac plane.
solution of CdS NRs, Ni-SAO and ascorbic acid was irradiated by using a
LED light (λ = 469 nm) as a light source. The generated gas samples were
analyzed by gas chromatograph (Agilent 7890A, with argon as a carrier
gas) equipped with a thermal conductivity detector (TCD) and 5 Å
molecular sieve column. Turnover numbers (TONs) for H
were calculated by using Equation (1) [18,19]:
2
production
num berofproductm olecules
num berofevolvedH
2
m olecules
TON =
=
(1)
num berofcocatalystm olecules num berofcocatalystm olecules
Fig. 2. (a) cyclic voltammogram (CV) of a solution of 6.0
acetonitrile. (b) CVs of a solution of 6.0 M Ni-SAO with varying amounts of
acetic acid in acetonitrile. Conditions: 0.10 M [n-Bu N]ClO as supporting
μ
M Ni-SAO in
μ
2
.2. Synthesis of the nickel complex, Ni-SAO
4
4
electrolyte, scan rate: 100 mV/s, glassy carbon working electrode (1 mm
diameter), Pt counter electrode, Ag/AgNO3 reference electrode, Fc internal
standard (*).
The ligand, SAOH (0.2 mmol) was added to a solution of Ni
CH COO) O (0.10 mmol) in ethanol (20 mL) with stirring. After
⋅4H
(
3
2
2
2

C.-L. Wang et al.
Inorganic Chemistry Communications 131 (2021) 108780
3
. Results and discussion
3
.1. Characterization for the nickel complex, Ni-SAO
3 2
As shown in Scheme 1, the reaction of SAOH and Ni(CH COO)
afforded a new nickel complex, Ni-SAO, which is agreement with the
following measurements and analysis. Ni-SAO exhibited one ion at a
mass-to-charge ratio (m/z) of 311.0223 (Fig. S1), with mass and isotope
+
distribution pattern corresponding to [Ni-SAO-H] .
Crystal structure of Ni-SAO was determined by X-ray crystallog-
raphy, giving the results shown in Tables S1-S3 and Fig. 1. As shown in
Fig. 1, the nickel center is four-coordinated by two N atoms and two O
atoms from phenolic oxime ligand, with a square planar geometry. From
the data listed in Table S1, both bond lengths of the Ni-N1 and Ni-N1a
are 1.873(3) Å. And the bond length of Ni-O2 (1.8412(19) Å) is the
same as that of Ni-O2a. The bond angle of N1 ꢀ Ni ꢀ O2 angle (92.84
◦
(
10) ) is the same as that of the O2a ꢀ Ni ꢀ N1a angle. Both bond angles
Fig. 3. Hydrogen evolution kinetics obtained upon continuous visible irradia-
tion (λ = 469 nm) of a pH 4.5 solution containing 0.16 mg mLꢀ CdS NRs, 0.16
M ascorbic acid, and 0.01 mM Ni-SAO.
1
◦
of O2 ꢀ Ni ꢀ N1a and O2a ꢀ Ni ꢀ N1 are 87.17(10) . Moreover, the
ligand O ꢀ H hydrogen atom is involved in hydrogen bond with oxygen
atom of another ligand (Fig. 1). Distances between the O ꢀ H hydrogen
and the oxygen are in the range 1.90–2.55 Å (Table S2).
aqueous buffer. Under ꢀ 1.45 V versus Ag/AgCl, only 39 mC of charge
was obtained from a neutral buffer during 2 min of electrolysis (Fig. S8).
Surprisingly, the introduction of Ni-SAO led to the formation of 2794 mC
of charge under the same conditions (Fig. S8). Together the data listed in
Fig. S9 with Equations (2) and (3) [29,30], the turnover frequency (TOF)
and overpotential (OP) were estimated, respectively. As depicted in
Fig. S10, when an OP was 837.6 mV, the TOF for hydrogen generation
Power X-ray diffraction (PXRD) was used to check the purity of Ni-
SAO, giving the result shown in Fig. S2. The theoretical patterns were
consistent with the experimental ones, indicating that a single phase of
Ni-SAO is formed.
To further characterize Ni-SAO, infrared spectra of the nickel com-
plex, Ni-SAO and the ligand, SAOH were measured, with the results
ꢀ
1
shown in Fig. S3. Compared with the ligand, SAOH (
ν
O-H = 3400 cm ),
was 1428 mol of hydrogen per mole of catalyst per hour (mol H
catalyst/h).
2
/mol
ꢀ 1
Ni-SAO showed the O-H stretching at 3000 cm . This can be attributed
to the formation of intramolecular hydrogen bond among oximino hy-
droxyl groups.
TOF = ΔC/(F*n
1
*n
2
*t)
(2)
To determine oxidation state of the nickel center, X-ray photoelec-
tron spectroscopy (XPS) spectra of Ni-SAO were measured. From Fig. S4
Overpotential = Applied potential ꢀ E(pH) =
Applied potential ꢀ ( ꢀ 0.059pH)
(
3)
(
a), the sample contains C, N, O, and Ni elements. As shown in Fig S4(b),
According to Fig. S11, 11.51 mL of H
2
was generated during 1 h
the main characteristic peaks at 855.5 eV and 872.8 eV can be assigned
to Ni 2p3/2 and Ni 2p1/2, respectively. The peaks centered at 860.7 eV
and 877.2 eV are the satellite peaks of Ni 2p3/2 and Ni 2p1/2, respec-
tively, a typical characteristic of Ni(II) oxidation state. These are
consistent with the results reported in the literature [23].
electrolysis using Ni-SAO as an electrocatalyst, with 31C charge accu-
mulation (Fig. S12). To evaluate Faraday efficiency (FE) of Ni-SAO for
hydrogen evolution, the CPE experiment was conducted in a 1.0 M po-
tassium chloride solution [31]. Based on the data shown in Fig. S13, the
Faraday efficiency was estimated to be 99%.
3
.2. Electrochemical investigation
3
.4. Photocatalytic behavior of Ni-SAO for hydrogen evolution
Electrochemical properties of Ni-SAO and the related components
were studied by cyclic voltammetry (CV) under N
on that no reduction waves were found for the ligand (SAOH) or Ni
CH COO)
(Fig. S5), Ni-SAO had three redox waves at ꢀ 1.16 V, ꢀ 1.43
and ꢀ 1.74 V (versus Ag/AgNO
2
atmosphere. Based
It is apparent that CdS, which has a narrow band gap (Eg = 2.4 eV),
can act as a photocatalyst for hydrogen evolution under blue light
conditions, however, the photocatalytic activity is very low due to the
high-rate charge recombination of photogenerated electron [32-34]. To
suppress this recombination and improve the photocatalytic activity, we
tried to introduce Ni-SAO as a cocatalyst on CdS. The photocatalytic
activity of Ni-SAO for hydrogen generation was investigated under blue
light using CdS NRs (Fig. S14(a)) as a photosensitizer, ascorbic acid as an
electron donor and Ni-SAO as a co-catalyst (Fig. S14(b)).
(
3
2
III/II
3
), which can be assigned to the Ni
,
II/I
I/0
Ni and Ni couples, respectively (Fig. 2(a)). Moreover, according to
1
/2
Figs. S6(a) and S6(b), the linear fitting plot of i
d
vs
ν
for Ni-SAO in-
dicates that the reduction is in a diffusion-controlled regime [24].
To research catalytic activity of Ni-SAO for proton reduction,
CH
3
COOH (AcOH) was introduced as a proton source (pKa = 23.51)
[
25]. As can be seen from Fig. 2(b), upon addition of AcOH, catalytic
To optimize the conditions for hydrogen production, a series of ex-
periments were conducted with varying pH, ascorbic acid concentration,
or amounts of photosensitizer. To explore the dependent activity of H2
production on the effect of pH, we performed photolysis experiments
with varying pH values. As shown in Fig. S15, an optimum pH for
photocatalytic H2 generation mediated by Ni-SAO (0.01 mM) was
II/I
I/0
current dramatically enhanced at the Ni
and Ni
redox couples,
suggesting that an electro-catalytic proton reduction occurred at the
II/I
I/0
Ni and Ni couples [26,27].
Next, the electrochemical properties of Ni-SAO were investigated an
aqueous medium. It was observed that catalytic current increases with
an increase in the concentration of Ni-SAO (Fig. S7(a)). Moreover, with
the decrease of pHs, the catalytic current increased (Fig. S7(b)), which
were consistent with a catalytic process [28].
ꢀ 1
observed at pH 4.5, with a TON of 2500 mol of H (mol of cat) during
2
3 h of irradiation. Next, we examined the dependence of amounts of
photosensitizer on H production with varying amounts of CdS NRs from
2
ꢀ 1
0
to 0.2 mg⋅mL , while maintaining the concentration of Ni-SAO (0.01
3
.3. Electrocatalytic hydrogen evolution by Ni-SAO
mM) and keeping all other reaction conditions constant. As shown in
Fig. S16, with the increase of CdS NRs, the activity for hydrogen evo-
ꢀ
1
To assess the electrocatalytic activity of Ni-SAO for H
2
evolution,
lution increased until a highest TON of 2777 mol of H
2
(mol of cat)
ꢀ
1
controlled potential electrolysis (CPE) experiments were conducted in
was reached at 0.16 mg⋅mL . Moreover, similar experiments were
3

C.-L. Wang et al.
Inorganic Chemistry Communications 131 (2021) 108780
Table 1
2
Photocatalytic activities of some reported nickel-based catalysts for H evolution.
ꢀ
1
Catalysts
Photosensitizer
Electron donor
Light source
TONmol H
2
(mol of cat)
Ref.
Ni-SAO
CdS nanorods
CdS nanorods
CdS nanorods
CdS nanorods
Ascorbic acid
Ascorbic acid
Ascorbic acid
Lactic acid
Blue light
Blue light
Blue light
λ = 420 nm
8138
This work
[35]
Ni-ATSM
11,500
24,900
9710
[
(bpte)NiCl
2
]
[36]
Nickel nanoparticles
[18]
2
H ATSM: Diacetyl-2-(4-N-methyl-3-thiosemicarbazone)-3-(4-N-amino-3-thiosemicarbazone); bpte: S,S-bis(2-pyridylmethyl)-1,2-thioethane.
-1
-2
-3
-4
-5
-6
-
1.88eV
LUMO
-5.43eV
HOMO
Fig. 5. HOMO-LUMO energy level diagram of Ni-SAO.
Fig. 4. Photocatalytic H
and an apparent quantum yield (AQY) of Ni-SAO under monochromatic light (λ
469 nm). Conditions: 0.16 mg CdS NRs, 0.010 mM Ni-SAO and 0.16 M
2
production of NiSAO under visible light (λ = 469 nm)
2
5
CdS NRs
CdS NRs/Ni-SAO
=
ascorbic acid (pH 4.5).
20
15
performed on varying contents of ascorbic acid, with the results listed in
Fig. S17. The highest value of TON of 2918 mol H
obtained by using 0.16 M ascorbic acid.
2
(mol cat.)-1 was
On the basis of the above observed results, an optimal three-
component photocatalytic system (pH 4.5) containing 0.01 mM Ni-
1
0
ꢀ
1
SAO, 0.16 mg⋅mL CdS NRs and 0.16 M ascorbic acid was provided.
The time courses of observed products under this optimal photocatalytic
5
0
system are shown in Fig. 3. The H
2
evolution process was ceased after 50
-
1
h irradiation, with a TON of 8138 mol H
2
(mol cat) .
Making a comparison for the photocatalytic activity among different
catalytic systems in term of TON values is not easy, because of possible
differences in the experimental conditions conducted and calculated
methods, etc. The activities for hydrogen evolution of some reported
photocatalytic systems [18,35,36] were listed in Table 1.
5
0
100
150
200
250
300
350
Time (s)
Fig. 6. The transient photocurrent responses of CdS NRs with or without
Ni-SAO.
The apparent quantum yields (AQYs) were measured under mono-
chromic light with a band-pass filter (λ = 469 nm). Based on the data
listed in Fig. 4 and Equation (4) [19], the AQYs of the photocatalytic
high resolution XPS spectrum of Ni 2p in the mixture of CdS NRs and Ni-
SAO is shown in Fig. S19(d). Before irradiation, two appreciable Ni 2p
peaks are observed at 855.43 eV and 872.76 eV, indicating the presence
system for H
Fig. 4. The average of AQY was about 10.24% during 10 h of irradiation.
AQY (%) = (2⋅nH2 ⋅N ⋅h⋅c)/(tirr ⋅λ⋅I⋅A)⋅100 (4)
2
generation were calculated, with the results listed in
2+
of a Ni ion. In contrast, no apparent Ni 2p peaks can be seen in the
A
sample after irradiation, further confirming no metallic nickel formation
during 50 h photocatalysis.
3
.5. Stability of the photocatalytic system
3
.6. Investigation for photocatalytic reaction mechanism
Powder X-ray diffraction (XRD) technology was used to examine the
stability of the photocatalytic system during irradiation. As shown in
Fig. S18, after 50 h irradiation, the peaks were agreement with the ones
before irradiation, indicating that both CdS NRs and Ni-SAO are stable
during 50 h of photolysis.
To explore more insights into the photocatalytic reaction mecha-
nism, several measurements and analysis were performed. According to
the data listed in Fig. S20(a), the band gaps of CdS NRs and CdS NRs/Ni-
SAO were estimated to be 2.38 and 2.26 eV, respectively (Fig. S20(b)),
suggesting that light absorption range of CdS NRs is extended. Next, the
photoluminescence (PL) spectra were employed to investigate the pho-
tocatalytic mechanism for hydrogen generation [38]. As shown in
Fig. S21, CdS NRs had a strong PL emission peak at 675 nm, which can
be attributed to the band-band PL phenomenon of the photoinduced
charge carriers. Compared with CdS NRs, the addition of Ni-SAO led to a
Furthermore, XPS spectra of the related components were measured,
giving the results shown in Fig. S19. As shown in Fig. S19(a), both
survey spectra are quite similar, with the presence of Cd, S, Ni, O, and C
elements. Two main peaks at 405.02 eV and 411.69 eV are attributed to
Cd 3d of CdS NRs (Fig. S19(b)). And Two obvious peaks at 161.32 eV
and 162.53 eV can be assigned to S 2p of CdS NRs (Fig. S19(c)) [37]. The
4

C.-L. Wang et al.
Inorganic Chemistry Communications 131 (2021) 108780
CRediT authorship contribution statement
Chun-Li Wang: Data curation, Formal analysis, Investigation,
Writing – original draft. Hao Yang: Formal analysis, Investigation. Juan
Du: Formal analysis, Investigation. Shu-Zhong Zhan: Funding acqui-
sition, Project administration, Supervision, Writing – review & editing.
Declaration of Competing Interest
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
2
Scheme 2. Possible mechanism for H production by the photocatalytic system
This work was financially supported by the National Science Foun-
dation of China (No. 21271073 and 21875074), and the Student
Research Program (SRP) of South China University of Technology.
with Ni-SAO.
decrease on the emission peak intensity of CdS NRs. This result suggests
that the recombination of photogenerated electron is suppressed, and
the efficient separation of charge carriers is accelerated, letting more
free electrons transfer from CdS NRs to Ni-SAO [39]. This result is also
consistent with the following orbital calculation.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.inoche.2021.108780.
The orbital calculation for Ni-SAO was conducted using “Gaussian
B3LYP/6-31G”, giving the results shown in Fig. 5. The highest occupied
molecular orbital (HOMO) of Ni-SAO was ꢀ 5.43 eV and lowest unoc-
cupied molecular orbital (LUMO) was ꢀ 1.88 eV [40]. Based on that the
energy of the gap of Ni-SAO (3.55 eV) is higher than that of CdS (2.4 eV)
References
[
1] T.T. Yao, X.R. An, H.X. Han, J.Q.J. Chen, C. Li, Photoelectrocatalytic materials for
solar water splitting, Adv. Energy Mater. 8 (2018) 1800210.
[
32-34], the photogenerated electrons transfer from CdS NRs to Ni-SAO
[2] M.Z. Jacobson, Review of solutions to global warming, air pollution, and energy
security, Energy Environ. Sci. 2 (2009) 148–173.
is favorable. Moreover, the transient photocurrent responses of CdS
NRs/Ni-SAO exhibited much higher transient photocurrent than that of
CdS NRs (Fig. 6), indicating the higher electron-hole pairs separation in
CdS NRs/Ni-SAO. The electrochemical impedance spectroscopy (EIS)
was also used to check the electron transfer efficiencies of CdS NRs and
the mixture of CdS NRs and Ni-SAO, with the results shown in Fig. S22.
The mixture of CdS NRs/Ni-SAO exhibited a much smaller arc radius
than the CdS NRs, suggesting that CdS NRs/Ni-SAO has a lower electron
transfer resistance and higher electrical conductivity. Additionally,
based on the mixture of CdS NRs/Ni-SAO has lager surface area than Ni-
SAO (Fig. S23), more active sites for the catalytic hydrogen evolution
reactions are provided [41].
[
[
3] S. Cao, C.J. Wang, W.F. Fu, Y. Chen, Metal phosphides as Co-catalysts for
photocatalytic and photoelectrocatalytic water splitting, ChemSusChem. 10 (2017)
4306–4323.
4] F.J. Niu, D.G. Wang, F. Li, Y.M. Liu, S.H. Shen, T.J. Meyer, Hybrid
photoelectrochemical water splitting systems: from interface design to system
assembly, Adv. Energy Mater. 10 (2020) 1900399.
[5] W. Lubitz, H. Ogata, O. Rüdig er, E. Reijerse, Hydrogenases, Chem. Rev. 114
(2014) 4081–4148.
[
6] C.V. Popescu, S.D. Ding, P. Ghosh, M.B. Hall, M. Cohara, M o¨ ssbauer spectroscopy
and theoretical studies of iron bimetallic complexes showing electrocatalytic
hydrogen evolution, Inorg. Chem. 58 (2019) 7069–7077.
2
[7] D. Dolui, S. Ghorai, A. Dutta, Tuning the reactivity of cobalt-based H production
electrocatalysts via the incorporation of the peripheral basic functionalities, Coord.
Chem. Rev. 416 (2020), 213335.
[
[
8] A.Z. Haddad, S.P. Cronin, M.S. Mashuta, R.M. Buchanan, C.A. Grapperhaus, Metal-
Assisted ligand-centered electrocatalytic hydrogen evolution upon reduction of a
bis(thiosemicarbazonato)Cu(II) complex, Inorg. Chem. 56 (2017) 11254–11265.
9] C.L. Wang, H. Yang, J. Du, S.Z. Zhan, Effects of halogen ligands of complexes
supported by bis(methylthioether)pyridine on catalytic activities for
electrochemical and photochemical driven hydrogen evolution, Appl. Organomet.
Chem. 34 (2021), e6201.
Together the above observation, analysis, with the reported pro-
2
cedures [42-44], a possible photocatalytic mechanism for H production
is presented in Scheme 2. Under visible light, the electrons are excited
from the valance band to the conduction band (CB) of CdS in the process
of photocatalytic hydrogen production [45], and the electron transfer
from CdS to Ni-SAO is workable from the thermodynamic point [46].
This is like that the electron in the CB of a semiconductor is transferred
to a metal [47-49]. Then, the electrons generated from CdS are trans-
[
[
10] G.G. Luo, Y.H. Wang, J.H. Wang, J.H. Wu, R.B. Wu, A square-planar nickel
dithiolate complex as an efficient molecular catalyst for the electro- and
photoreduction of protons, Chem. Commun. 53 (2017) 7007–7010.
11] Z.H. Pan, Y.W. Tao, Q.F. He, Q.Y. Wu, L.P. Cheng, Z.H. Wei, J.H. Wu, J.Q. Lin,
D. Sun, Q.C. Zhang, D. Tian, G.G. Luo, The difference se makes: a bio-inspired dppf-
supported nickel selenolate complex boosts dihydrogen evolution with high oxygen
tolerance, Chem. Eur. J. 24 (2018) 8275–8280.
+
ferred to Ni-SAO and directly react with the adsorbed water/H to yield
H
2
. Meanwhile, ascorbic acid (sacrificial reagent) can provide electrons
for the valance band of CdS, and photogenerated holes are trapped.
[12] D. Basu, S. Mazumder, J. Niklas, H. Baydoun, D. Wanniarachchi, X.T. Shi, R.
J. Staples, O. Poluektov, H.B. Schlegel, C.N. Verani, Determination of enantiomeric
excess of carboxylates by fluorescent macrocyclic sensors, Chem. Sci. 7 (2016)
4
. Conclusions
3
264–3278.
[
[
13] T.W. Lyons, Q. Huanga, Effects of cyclohexane-monoxime and dioxime on the
electrodeposition of cobalt, Electrochim. Acta. 245 (2017) 309–317.
14] Z. Shaghaghi, M. Aligholivand, R. Mohammad-Rezaei, Enhanced water splitting
through different substituted cobalt-salophen electrocatalysts, Int. J. Hydrogen
Energy 46 (2021) 389–402.
In summary, we demonstrate the synthesis of a square plane nickel
complex, Ni-SAO, which has been fully characterized. Ni-SAO exhibits
good photocatalytic and electrocatalytic activity for H production.
2
[
[
15] A.M. Whyte, B. Roach, D.K. Henderson, P.A. Tasker, M.M. Matsushita, K. Awaga, F.
J. White, P. Richardson, N. Robertson, Structural, magnetic, and electronic
properties of phenolic oxime complexes of Cu and Ni, Inorg. Chem. 50 (2011)
12867–12876.
Based on that Ni-SAO can effectively extend the visible light absorption
region of CdS NRs and reduce the recombination rate of photoinduced
electrons in CdS NRs, as a co-catalyst, Ni-SAO can photo-catalyze
hydrogen evolution. Moreover, DFT calculation of Ni-SAO also in-
dicates that the electrons in the CB of CdS can be transferred to the nickel
center of Ni-SAO. This finding may afford a new method for the design of
catalyst for hydrogen evolution.
16] J.S. Jang, U.A. Joshi, J.S. Lee, Solvothermal synthesis of CdS nanowires for
photocatalytic hydrogen and electricity production, J. Phys. Chem. C. 111 (2007)
1
3280–13287.
[17] S.R. Joshi, S.P. Pachling, S.I. Habib, Metal complexes of salisylaldoxime:
Preparation characterisation and biological activity, Inorganic chemistry. 9 (2014)
1
02–108.
5

C.-L. Wang et al.
Inorganic Chemistry Communications 131 (2021) 108780
[35] W.X. Jiang, Z.L. Xie, S.Z. Zhan, A photocatalytic system with a bis
[
H
18] S. Cao, C.J. Wang, X.J. Lv, Y. Chen, W.F. Fu, A highly efficient photocatalytic 2
evolution system using colloidal CdS nanorods and nickel nanoparticles in water
under visible light irradiation, Appl. Cata. B: Environ. 162 (2015) 381–391.
19] D.J. Martin, K.P. Qiu, S.A. Shevlin, A.D. Handoko, X.W. Chen, Z.X. Guo, J.W. Tang,
(thiosemicarbazonato)-nickel over CdS nanorods for hydrogen evolution from
water under visible light, Inorg. Chem. Commun. 102 (2019) 5–9.
[36] J.M. Lei, S.P. Luo, S. Zhan, Photocatalytic system with water soluble nickel
complex of S, S’-bis(2-pyridylmethyl)-1,2-thioethane over CdS nanorods for
hydrogen evolution from water under visible light, Int. J. Hydrogen Energy 43
(2018) 19047–19056.
[
Highly efficient photocatalytic
H
2 evolution from water using visible light and
structure-controlled graphitic carbon nitride, Angew. Chem. Int. Ed. 53 (2014)
9
240–9245.
[
[
20] G.M. Sheldrick, SHELXT-integrated space-group and crystal-structure
determination, Acta Cryst, A 71 (2015) 3–8.
[37] Y.T. Chen, J.B. Ding, Y. Guo, L.B. Kong, H.L. Li, A facile route to preparation of CdS
nanorods, Mater. Chem. Phys. 77 (2003) 734–737.
21] O.V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H. Puschmann, OLEX2:
a complete structure solution, refinement and analysis program, J. Appl. Cryst. 42
[38] X. Lin, Y.S. Wang, J. Zheng, C. Liu, Y. Yang, G.B. Che, Graphene quantum dot
sensitized leaf-like InVO
4 4
/BiVO nanostructure: a novel ternary heterostructured
(
2009) 339–341.
QD-RGO/InVO /BiVO composite with enhanced visible-light photocatalytic
activity, Dalton Trans. 44 (2015) 19185–19193.
4
4
[
[
22] G.M. Sheldrick, Crystal structure refinement with SHELXL, Acta Cryst, C 71 (2015)
3
–8.
[39] R.M. Irfan, D.C. Jiang, Z.J. Sun, L. Zhang, S.S. Cui, P.W. Du, Incorporating a
molecular co-catalyst with a heterogeneous semiconductor heterojunction
photocatalyst: Novel mechanism with two electron-transfer pathways for enhanced
solar hydrogen production, J. Catalysis 353 (2017) 274–285.
23] B. Sarkara, W. Kweka, D. Verma, J. Kima, Effective vacuum residue upgrading
using sacrificial nickel(II)dimethylglyoxime complex in supercritical methanol,
Appl. Catal. A. Gener. 545 (2017) 148–158.
[
24] D. Hong, Y. Tsukakoshi, H. Kotani, T. Ishizuka, K. Ohkubo, Y. Shiota, K. Yoshizawa,
S. Fukuzumi, T. Kojima, Mechanistic insights into homogeneous electrocatalytic
and photocatalytic hydrogen evolution catalyzed by high-spin Ni(II) complexes
[40] I.B. Obot, N.O. Obi-Egbedi, Theoretical study of benzimidazole and its derivatives
and their potential activity as corrosion inhibitors, Corrosion Sci. 52 (2010)
657–660.
with S
N
2 2
-type tetradentate ligands, Inorg. Chem. 57 (2018) 7180–7190.
[41] S. Wang, B.C. Zhu, M.J. Liu, L.Y. Zhang, J.G. Yu, M.H. Zhou, Direct Z-scheme ZnO/
[
[
[
25] E. Raamat, K. Kaupmees, G. Ovsjannikov, A. Trummal, A. Kütt, J. Saame, I. Koppel,
I. Kaljurand, L. Lipping, T. Rodima, V. Pihl, I.A. Koppel, I. Leito, Acidities of strong
neutral Brønsted acids in different media, J. Phys. Org. Chem. 26 (2013) 162–170.
26] A.M. Appel, D.L. DuBois, M.R. DuBois, Molybdenum-Sulfur dimers as
electrocatalysts for the production of hydrogen at low overpotentials, J. Am. Chem.
Soc. 127 (2005) 12717–12726.
H
CdS hierarchical photocatalyst for enhanced photocatalytic 2-production activity,
Appl. Catal. B: Environ. 243 (2019) 19–26.
[42] L. Wang, N. Xu, X.Y. Pan, Y.S. He, X.X. Wang, W.Y. Su, Cobalt lactate complex as a
H
hole cocatalyst for significantly enhanced photocatalytic 2 production activity
over CdS nanorods, Catal. Sci. Technol. 8 (2018) 1599–1605.
[43] Z. Han, L. Shen, W.W. Brennessel, P.L. Holland, R. Eisenberg, Nickel
pyridinethiolate complexes as catalysts for the light-driven production of hydrogen
from aqueous solutions in noble-metal-free systems, J. Am. Chem. Soc. 135 (2013)
14659–14669.
27] P. Gotico, D. Moonshiram, C.M. Liu, X.Y. Zhang, R. Guillot, A. Quaranta, Z. Halime,
W. Leibl, A. Aukauloo, Spectroscopic characterisation of a bio-inspired Ni-based
N S
proton reduction catalyst bearing a pentadentate 2 3 ligand with improved
photocatalytic activity, Chem. Eur. J. 26 (2020) 2859–2868.
[44] W. Zhang, J. Hong, J. Zheng, Z. Huang, J. Zhou, R. Xu, Nickel–thiolate complex
[
28] S.K. Padhi, E. Ahmad, S. Rai, Kinetics and the potential well in electrochemical
2
catalyst assembled in one step in water for solar H production, J. Am. Chem. Soc.
2
+
hydrogen evolution by [Co(4-tolyl-tpy)
36000.
2
]
, Electrochim. Acta 340 (2020),
133 (2011) 20680–20683.
1
H
[45] T.M. Di, B.C. Zhu, J. Zhang, B. Cheng, J.G. Yu, Enhanced photocatalytic 2
[
[
29] V. Artero, J.M. Saveant, Toward the rational benchmarking of homogeneous H
2
-
production on CdS nanorod using cobalt-phosphate as oxidation cocatalyst, Appl.
Sur. Sci. 389 (2016) 775–782.
evolving catalysts, Energy Environ. Sci. 7 (2014) 3808–3814.
30] R.S. Nichloson, I. Shain, Theory of stationary electrode polarography. single scan
and cyclic methods applied to reversible, irreversible, and kinetic systems, Anal.
Chem. 36 (1964) 706–723.
[46] T.M. Di, L.Y. Zhang, B. Cheng, J.G. Yu, J.J. Fan, CdS nanosheets decorated with
H
Ni@graphene core-shell cocatalyst for superior photocatalytic 2 production,
J. Mater. Sci. Technol. 56 (2020) 170–178.
[
[
31] H.I. Karunadasa, C.J. Chang, J.R. Long, A molecular molybdenum-oxo catalyst for
generating hydrogen from water, Nature. 464 (2010) 1329–1333.
32] B. Zhang, W.F. Yao, C.P. Huang, Q.J. Xu, Q. Wu, Shape effects of CdS
photocatalysts on hydrogen production, Int. J. Hydrogen Energy 38 (2013)
[47] R. Costi, A.E. Saunders, E. Elmalem, A. Salant, U. Banin, Visible light-induced
charge retention and photocatalysis with hybrid CdSeꢀ Au nanodumbbells, Nano
Lett. 8 (2008) 637–641.
[48] S. Chen, S. Thota, G. Reggiano, J. Zhao, Generalized seeded growth of Ag-based
metal chalcogenide nanorods via controlled chalcogenization of the seeds,
J. Mater. Chem. C. 3 (2015) 11842–11849.
7
224–7231.
[
[
33] Z.J. Sun, Q.D. Yue, J.S. Li, J. Xu, H.F. Zheng, P.W. Du, Copper phosphide modified
cadmium sulfide nanorods as a novel p–n heterojunction for highly efficient
visible-light-driven hydrogen production in water, J. Mater. Chem. A. 3 (2015)
[49] B. Tahir, M. Tahir, N.S. Amin, Gold–indium modified TiO
photocatalytic CO reduction with H
Appl. Surf. Sci. 338 (2015) 1–14.
2
nanocatalysts for
as reductant in a monolith photoreactor,
2
2
1
0243–10247.
34] Q.Z. Wang, J.J. Li, Y. Bai, J.H. Lian, H.H. Huang, Z.M. Li, Z.Q. Lei, W.F. Shang,
Long-chain aliphatic polyesters from plant oils for injection molding, film extrusion
and electrospinning, Green Chem. 16 (2014) 2728–2735.
6