Self-supporting highly branched urchin-like NiCoP/NiFeP heterostructures as efficient bifunctional electrocatalyst for overall water splitting

The development of low-cost, efficient, and stable electrocatalysts is urgent in sustainable energy devices. Bifunctional catalysts are particularly crucial because they surmount the kinetics limitations stemming from the sluggish mechanism associated with hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) in water electrolysis. Herein, self-supporting highly branched urchin-like NiCoP/NiFeP heterostructures were in situ grown on Ni foam (NF) through hydrothermal and phosphorization treatments, as examined by a set of characterizations. The role of the compositions played within the material was rigorously investigated to maximize the catalytic properties, coupled by elaborating the catalytic mechanism. The optimized NiCoP/NiFeP/NF exhibited superior performance with the boosted HER activity (overpotential of 43 mV @ 10 mA cm⁻² and 120 mV @ 100 mA cm⁻²) and high OER activity (overpotential of 261 mV @ 50 mA cm⁻² and 299 mV @ 100 mA cm⁻²). Notably, the two-electrode electrolyzer assembled with the NiCoP/NiFeP/NF achieved a cell voltage of 1.705 V at 100 mA cm⁻², integrated by keeping stable operation over 100 h. In all, this research sheds some light on preparation of advanced catalysts in electrocatalysis and energy devices, potentially paving the way for efficient and sustainable energy technologies.