Co₂P-NiMoN/NF Heterostructure Nanorod Arrays as Efficient Bifunctional Electrocatalysts for Urea Electrolysis

Electrolysis of water represents an effective method for the generation of high-purity hydrogen. Nevertheless, the anodic oxygen evolution reaction (OER) exhibits slow kinetics, which leads to a high electrolytic potential and induces excessive energy consumption. In this work, nickel foam-supported 3D phosphide/bimetal nitride (Co₂P-NiMoN/NF) nanorod array catalyst is prepared by calcination of NiMoO₄, followed by phosphatization of Co(OH)₂. The heterostructure catalyst exhibits excellent catalytic activity for cathodic hydrogen evolution reaction (HER: <i>η</i>₁₀₀ = 98 mV, <i>η</i>₁₀₀₀ = 297 mV) and anodic OER (<i>η</i>₁₀₀ = 277 mV, <i>η</i>₁₀₀₀ = 382 mV) of water electrolysis in alkaline electrolyte, indicating its feasibility as a bifunctional catalyst for overall water splitting (OWS). Additionally, at a current density of 100 mA cm^-2, the associated oxidation potential is decreased by roughly 160 mV when the anodic OER is replaced with the urea oxidation process (UOR), which has a far lower thermodynamic equilibrium potential. Density functional theory (DFT) calculations reveal that the heterointerface between Co₂P and NiMoN enriches the density of electronic states near the Fermi level, thereby enhancing electron transfer and promoting charge redistribution. This modulation precisely tunes the adsorption strengths of reactants during the reaction process, ultimately boosting the electrocatalytic performance. A current density of 100 mA cm^-2 can be attained at a cell voltage of 1.51 V when Co₂P-NiMoN/NF is used as the anode and cathode in the urea electrolysis cell. Notably, this cell potential is significantly lower compared to that of the water electrolysis cell (1.65 V), as well as the previously published values. The findings demonstrate that the Co₂P-NiMoN/NF heterostructure can be used as a bifunctional catalyst for water and urea electrolysis and demonstrate an efficient strategy for the energy-efficient production of hydrogen through substituting UOR for OER at the anode of water electrolysis.