Highly active catalyst derived from a 3D foam of Fe(PO₃)₂/Ni₂P for extremely efficient water oxidation

Commercial hydrogen production by electrocatalytic water splitting will benefit from the realization of more efficient and less expensive catalysts compared with noble metal catalysts, especially for the oxygen evolution reaction, which requires a current density of 500 mA/cm² at an overpotential below 300 mV with long-term stability. Here we report a robust oxygen-evolving electrocatalyst consisting of ferrous metaphosphate on self-supported conductive nickel foam that is commercially available in large scale. We find that this catalyst, which may be associated with the in situ generated nickel-iron oxide/hydroxide and iron oxyhydroxide catalysts at the surface, yields current densities of 10 mA/cm² at an overpotential of 177 mV, 500 mA/cm² at only 265 mV, and 1,705 mA/cm² at 300 mV, with high durability in alkaline electrolyte of 1 M KOH even after 10,000 cycles, representing activity enhancement by a factor of 49 in boosting water oxidation at 300 mV relative to the state-of-the-art IrO₂ catalyst.