Electronic structure regulation of NiO_xvia partial phosphorization for efficient oxygen evolution

Electrocatalytic water splitting is a promising approach for sustainable hydrogen production, but its efficiency is hindered by the sluggish kinetics of the oxygen evolution reaction (OER). To develop highly active and durable OER electrocatalysts, we developed a partial phosphorization strategy to reconstruct the electronic structure of NiO_x through the in situ formation of a small amount of Ni₂P. Specifically, with iron foam (IF) as the substrate, the partially phosphorized NiO_x/Ni₂P heterostructure was constructed by phosphorizing the NiO_x precursor (NiO_x/Ni₂P@IF). The introduction of a small amount of Ni₂P reconstructs the electronic structure of the NiO_x phase, leading to a higher electron density of Ni sites in NiO_x, which substantially weakens the adsorption of oxygenated species on NiO_x/Ni₂P@IF, thereby enhancing the OER performance. As a result, NiO_x/Ni₂P@IF exhibits significantly superior OER activity compared with NiO_x on IF (NiO_x@IF) and the commercial RuO₂, requiring a low overpotential of only 345 mV at 100 mA cm^-2 while maintaining stable operation for 1000 h. Furthermore, when employed as the anode for overall water splitting, NiO_x/Ni₂P@IF requires a low cell voltage of only 1.89 V to deliver 100 mA cm^-2 and operates continuously for over 100 h with negligible activity decay. This work provides an effective strategy for regulating the electronic structure of oxide precursors through partial phosphorization, offering new insights into the design of high-performance OER electrocatalysts.