Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao, 066004, China.
Nanoscale. 2018 Jun 7;10(22):10459-10466. doi: 10.1039/c8nr02402b.
Developing an efficient non-noble bifunctional electrocatalyst for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in the same electrolyte is significant for lowering the cost of electrochemical water splitting. Herein, a phase-pure pentlandite Ni4.3Co4.7S8 bifunctional electrocatalyst was synthesized via a hydrothermal process using a commercial nickel foam as the nickel source. The active metallic nickel source and the chelating agent ethylenediamine play important roles in the formation of phase-pure pentlandite Ni4.3Co4.7S8 binary sulfide. Physicochemical characterizations, electrochemical measurements and density functional theory (DFT) computations illustrate that the material has an exposed high-indexed (022) surface with a biomimetic hydrogenase-like structure, and that the pentlandite phase has metallic characteristics, with next-nearest neighbor metal-metal bonds, as well as there being a high overlap of density of state (DOS) at the Fermi-level due to the synergistic effect between Ni and Co ions. In addition, there is an elevation of the d-state center (from -2.84 to -1.52 eV) with high occupation of the anti-bonding eg (dx2-y2 and dz2) d-orbitals. These properties endow the Ni4.3Co4.7S8 bifunctional electrocatalyst with higher catalytic activity for OER than RuO2, with comparative activity for HER to commercial Pt/C and with a low over-potential for all water splitting in an alkaline electrolyte. The studies here provide a novel strategy to synthesise phase-pure pentlandite nickel cobalt binary sulfides and boost their applications in electrochemical water splitting.
开发一种高效的非贵金属双功能电催化剂，使其能够在同一电解质中同时进行析氧反应（OER）和析氢反应（HER），对于降低电化学水分解的成本具有重要意义。在此，通过水热法使用商业镍泡沫作为镍源合成了相纯的镍钴硫化物 Ni4.3Co4.7S8 双功能电催化剂。活性金属镍源和螯合剂乙二胺在相纯的镍钴硫化物 Ni4.3Co4.7S8 二元硫化物的形成中起着重要作用。物理化学特性、电化学测量和密度泛函理论（DFT）计算表明，该材料具有暴露的高指数（022）表面，具有仿生氢化酶样结构，并且镍钴硫化物相具有金属特性，具有最近邻金属-金属键，并且在费米能级处由于 Ni 和 Co 离子的协同作用，态密度（DOS）有很高的重叠。此外，d 态中心（从-2.84 到-1.52 eV）升高，反键 eg（dx2-y2 和 dz2）d 轨道的占据率很高。这些特性使 Ni4.3Co4.7S8 双功能电催化剂对 OER 的催化活性高于 RuO2，对 HER 的活性与商业 Pt/C 相当，并且在碱性电解质中对所有水分解的过电位都很低。本研究为合成相纯的镍钴二元硫化物提供了一种新策略，并推动了它们在电化学水分解中的应用。
