State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University , Xi'an, Shaanxi 710049, People's Republic of China.
Institute of Materials Research and Engineering (IMRE), A*STAR (Agency for Science Technology and Research) , 2 Fusionopolis Way, Innovis #08-03, Singapore 138634.
ACS Nano. 2017 Nov 28;11(11):11031-11040. doi: 10.1021/acsnano.7b05050. Epub 2017 Oct 31.
The rational design and synthesis of nonprecious, efficient, and stable electrocatalysts to replace precious noble metals are crucial to the future of hydrogen economy. Herein, a partial sulfurization/phosphorization strategy is proposed to synthesize a nonstoichiometric pyrrhotite-type cobalt monophosphosulfide material (CoSP) with a hexagonal close-packed phase for electrocatalytic water splitting. By regulating the degree of sulfurization, the P/S atomic ratio in the cobalt monophosphosulfide can be tuned to activate the Co/Co couples. The synergy between the nonstoichiometric nature and the tunable P/S ratio results in the strengthened Co/Co couples and tunable electronic structure and thus efficiently promotes the oxygen/hydrogen evolution reaction (OER/HER) processes toward overall water splitting. Especially for OER, the CoSP material, featured with a uniform yolk-shell spherical morphology, shows a low overpotential of 266 mV at 10 mA cm (η) with a low Tafel slope of 48 mV dec as well as high stability, which is comparable to that of the reported promising OER electrocatalysts. Coupled with the high HER activity of CoSP, the overall water splitting is demonstrated with a low η at 1.59 V and good stability. This study shows that phase engineering and composition control can be the elegant strategy to realize the Co/Co couple activation and electronic structure tuning to promote the electrocatalytic process. The proposed strategy and approaches allow the rational design and synthesis of transition metal monophosphosulfides toward advanced electrochemical applications.
合理设计和合成非贵金属、高效、稳定的电催化剂来替代贵金属对于未来的氢能经济至关重要。在此，提出了一种部分硫化/磷化策略，用于合成具有六方密堆积相的非化学计量型磁黄铁矿型钴单磷硫化物（CoSP）材料，用于电催化水分解。通过调节硫化程度，可以调节钴单磷硫化物中的 P/S 原子比来激活 Co/Co 偶联。非化学计量性质和可调 P/S 比的协同作用导致增强的 Co/Co 偶联和可调谐的电子结构，从而有效地促进整体水分解的氧/氢析出反应（OER/HER）过程。特别是对于 OER，具有均匀的蛋黄壳球形形态的 CoSP 材料在 10 mA cm（η）时表现出低过电位 266 mV，具有低的 48 mV dec 的 Tafel 斜率以及高稳定性，可与报道的有前途的 OER 电催化剂相媲美。与 CoSP 的高 HER 活性相结合，整体水分解在 1.59 V 时表现出低 η 和良好的稳定性。本研究表明，通过相工程和组成控制可以实现 Co/Co 偶联的激活和电子结构的调谐，以促进电催化过程。所提出的策略和方法允许对过渡金属单磷硫化物进行合理的设计和合成，以实现先进的电化学应用。
