Photoelectrochemical Water Oxidation over Novel Semiconducting Zinc-Based Metal–Thiolate Framework

Designing an efficient catalyst for a sustainable photoelectrochemical
water oxidation reaction is very challenging in the context of renewable
energy research. Here, we have introduced a new semiconducting porous
zinc–thiolate framework via successful stitching of an “N”
donor linker with a triazine-based tristhiolate secondary building
unit in the overall architecture. The introduction of both linker
and tristhiolate ligand synergistically modifies the architecture
by making it a rigid, crystalline, three-dimensional, thermally stable,
and porous framework. Our novel zinc–thiolate framework is
used as an n-type semiconductor as revealed from the solid-state UV–vis
DRS spectroscopic analysis, ac and dc conductivity analysis, and Mott–Schottky
plot. This n-type semiconductor-based zinc–thiolate framework
is utilized in the photoelectrochemical water oxidation reaction.
It displayed a very high efficiency for a visible-light-driven oxygen
evolution reaction (OER) in a KOH medium using standard Ag/AgCl as
the reference electrode. The superiority of this material was further
revealed from the low onset potential (0.822 mV vs RHE), high photocurrent
density (0.204 mA cm–2), good stability, and high
O2 evolution rate (77 μmol g–1 of
oxygen evolution within 2 h), and a good efficiency (ABPE 0.42%, IPCE
29.6% and APCE 34.5%). Furthermore, the porosity in the overall framework
seems to be a blessing to the photoelectrochemical performance due
to better mass diffusion of the electrolyte. A detailed mechanism
for the OER reaction was analyzed through density functional theory
analysis suggesting the potential future of this Zn–thiolate
framework for achieving a high efficiency in the sustainable water
oxidation reaction.

在可再生能源研究领域，开发用于可持续光电化学水氧化反应的高效催化剂极具挑战性。本研究通过将氮给体连接体与三嗪基三硫醇次级结构单元（secondary building unit）成功组装，构筑了一种新型半导体多孔硫锌骨架。连接体与三硫醇配体的协同修饰，赋予该骨架刚性、结晶性、三维结构、热稳定性与多孔性。通过固态紫外-可见漫反射光谱（UV–vis DRS）、交流与直流电导分析以及莫特-肖特基（Mott–Schottky）曲线表征，证实该新型硫锌骨架属于n型半导体。将该n型半导体硫锌骨架应用于光电化学水氧化反应，在以标准Ag/AgCl为参比电极的KOH介质中，其展现出优异的可见光驱动氧析出反应（OER）催化性能。该材料的催化优势进一步体现为：低起始电位（0.822 mV vs RHE）、高光电流密度（0.204 mA cm⁻²）、良好的稳定性，以及高氧气析出速率（2小时内产氧量达77 μmol g⁻¹），同时具备优异的催化效率（ABPE 0.42%、IPCE 29.6%与APCE 34.5%）。此外，骨架的多孔结构可促进电解质的传质过程，从而对光电化学性能起到积极作用。本研究通过密度泛函理论（DFT）分析了OER反应的详细机理，结果表明该硫锌骨架在可持续水氧化反应中实现高效催化具有可观的应用前景。