Unveiling the Metal Incorporation Effect of Steady-Active FeP Hydrogen Evolution Nanocatalysts for Water Electrolyzer

Graphical This work reports the homogeneous incorporation of Co into the FeP host to promote both activity and stability of HER for the PEMWE application and demonstrates the probable origin of the high performance by ex situ experiments. Metal phosphides are promising noble metal-free electrocatalysts for hydrogen evolution reaction (HER), but they usually suffer from inferior stability and thus are far from the device applications. We reported a facile and controllable synthetic method to prepare metal-incorporated M-FeP nanoparticles (M=Cr, Mn, Co, Fe, Ni, Cu, and Mo) with the guide of the density functional theory (DFT). The evaluated HER activity sequence was consistent with the DFT predictions, and cobalt was revealed to be the appropriate dopant. With the optimization of the Co/Fe ratio, the Fe 0.67 Co 0.33 P/C only required overpotentials of 67 mV and 129 mV to obtain the cathodic current density of 10 and 100 mA cm −2, respectively. It maintained the initial activity in the 10 h stability test, surpassing the other Co-FeP/C catalysts. Ex situ experiments demonstrated that the decreased element leaching and the increased surface phosphide content contributed to the high stability of the Fe 0.67 Co 0.33 P/C. A proton exchange membrane water electrolyzer was assembled using the Fe 0.67 Co 0.33 P/C as the cathodic catalyst. It showed a current density of 0.8 A cm −2 at the applied voltage of 2.0 V and retained the initial activity in the 1000 cycles’ stability test, suggesting the potential application of the catalysts.