Hierarchical Nanostructured Co-Doped AgP2/CoP Nanoelectrocatalyst for Low-Overpotential Urea Electrooxidation

Abstract

Urea oxidation reaction (UOR) represents a promising route for sustainable hydrogen generation and wastewater purification, serving as an energy-saving alternative to the oxygen evolution reaction. Here, we develop a Co-doped AgP2/CoP nanoelectrocatalyst (denoted as CoAgP2/CoP), which forms a hierarchical nanostructure. The nanoelectrocatalyst demonstrates excellent UOR performance, requiring a low onset potential of 1.23 V vs RHE to deliver 10 mA cm–2, exhibiting a small Tafel slope of 23.36 mV dec–1, and maintaining remarkable stability for over 240 h in alkaline urea electrolyte. Experimental characterization confirms that Co species are oxidized into catalytically active Co3+ species, while phosphorus is transformed into oxidized P–O species that stabilize the active interface, and Ag facilitates electron transfer. Mechanistic investigations reveal that, within the composite hierarchical framework, urea undergoes sequential N–H and C–N bond cleavage at the P-assisted Co3+ active sites. The addition of Ag further reduces the energy barrier for generating high-valence active species. The hierarchical nanoarchitecture enlarges the electrochemically active surface area and enhances mass transport. This work highlights the synergistic effects arising from the multielement composition and hierarchical nanostructure in promoting urea electrooxidation, providing a feasible strategy toward energy-efficient hydrogen production and environmental remediation.