Electrically driven phosphorus dissolution from iron-nickel phosphate surfaces exposing highly active sites for oxygen evolution reaction.

The enhancement of catalytic activity can be achieved by removing non-active components from the surface of catalyst materials, thereby increasing the accessibility of active sites. In this study, an electrically driven method is described for the removal of non-active phosphorus (P) to optimize the surface composition of iron-nickel phosphide (denoted as P-O-NFF), resulting in the exposure of more active Fe-Ni sites for oxygen evolution reaction (OER). The optimized P-O-NFF electrode exhibits exceptional OER catalytic activity, with an overpotential of 217 mV at 10 mA cm^-2. Furthermore, it demonstrates significant stability, maintaining a 100 % voltage retention rate after 300 h at a high current density of 200 mA cm^-2. The superior performance can be attributed to the disruption of the original crystalline lattice during the electrically driven P dissolution, which leads to the formation of amorphous Fe-Ni hydroxide/oxyhydroxide that enhances active sites exposure. This work offers a simple and effective method for controlling the surface component of catalysts to enhance their catalytic performance, which has the potential to advance industrial water electrolysis technology.