One-step engineering Co8FeS8 electrocatalyst based on Co-Fe bimetal foam for a highly-efficient oxygen evolution reaction

The sluggish oxygen evolution reaction (OER) is still the bottleneck problem for a highly efficient hydrogen generation by water splitting. Herein, the CoFe bimetallic foam (CFF) is used for the one-step hydrothermalvulcanization to engineer the special crystal structure of CoFe sulfide (Co8FeS8/CFF), and the resulting electrocatalyst of Co8FeS8/CFF demonstrates a remarkable OER performance in 1 M KOH electrolyte, which only requires 73 mV to drive a current density of 10 mA cm-2 (j10). Meanwhile, the chronoamperometry curve further demonstrates the good electrocatalytic stability of Co8FeS8/CFF, and the I-t curve maintains for 20 h at a current density of j15. Furthermore, the theoretical calculations reveal that the (311) facet of Co8FeS8 serves a crucial role in the OER process, and the Fe site is more conducive to transfer electrons, facilitating the OER process. Noticeably, the reported one-step hydrothermal-vulcanization method successfully synthesized the Co8FeS8/CFF electrocatalyst at a low cost. The significance of Fe sites on the Co8FeS8/CFF (311) plane for the OER process was confirmed through DFT calculations, further enhancing the application potential of transition-metal-based sulfides in the field of water splitting.