Activating Fe activity and improving Ni activity via C3N4 substrate in alkaline oxygen evolution catalyzed by Ni-Fe phosphide

Ni phosphides have recently attracted considerable attention as promising catalysts for the oxygen evolution reaction (OER) and are generally promoted by Fe incorporation. However, the catalytic performance of nickel phosphide still does not meet the desired expectations. Additionally, the catalytic activity of iron (Fe) is insignificant and can be disregarded. In this study, we used C3N4 as a carbon substrate to modulate the 3d electron configurations and adsorption properties of Ni and Fe. Density functional theory (DFT) analysis reveals that the catalytic performance of Ni sites can be enhanced by utilizing the C3N4 substrate. Surprisingly, the Fe sites can also be activated to catalyze OER through a direct O2 mechanism and the catalytic activity of Fe is found to surpass that of Ni. As a result, the FeNi-C3N4-P catalyst demonstrated remarkable catalytic performance for OER. It exhibited a Tafel slope of 40.4 mV dec-1, an overpotential of 235 mV at 100 mA cm-2, and exhibited exceptional stability. This study highlights the activation of Fe and the enhancement of Ni by utilizing nitrogen-containing carbon substrates. This strategy offers promising prospects for the development of efficient Ni/Fe-based OER catalysts.