Enhanced Water Splitting Electrocatalysis with Heterointerfacial Cobalt Phosphide In Situ Supported on a...

The active site density, intrinsic activity, and supporting substrate of cobalt phosphide catalysts are vital to their performance in alkaline water electrolysis. In this work, a CoP/Co₂P loaded on cellulose nanofiber-derived carbon aerogels (CP/CCAs) bifunctional electrocatalyst with a three-dimensional network and heterostructure is illustrated through sequential facile hydrothermal, freeze-drying, and phosphorylation processes. The three-dimensional network of carbon aerogels derived from cellulose nanofibers reveals a specific surface area of 183.41 m²/g, greatly enriching the active sites and facilitating the electron and mass transportation. Besides, interactions between CoP/Co₂P with a heterogeneous structure and carbon aerogels modulate the electronic structure to enhance the intrinsic activity of the catalysts. Benefiting from these advantages, CP/CCAs-2 demonstrates a superior oxygen evolution reaction activity (η10 mA cm^-2 = 277 mV) over the benchmark RuO₂ and a moderate hydrogen evolution reaction performance (η10 mA cm^-2 = 63 mV). Density functional theory calculations further reveal that the coupling of CoP/Co₂P and cellulose-derived carbon aerogels promotes the water adsorption and activates the H-O bond. As a result, the alkaline electrolyzer assembled with CP/CCAs-2 both as a cathode and an anode shows a low cell voltage of 1.59 V at a current density of 10 mA cm^-2 and good stability. This work provides a strategy for phosphide electrocatalysts composited with green carbon carriers for overall water splitting.