High-entropy-driven kinetic steering of urea electrooxidation enables coupled nitrite reduction for rapid urea-to-nitrogen conversion.
Yu Chunmu C, Li Xin X, Zhang Hao H, Fan Qingjuan Q et al.
The electrochemical urea oxidation reaction (UOR) is thermodynamically favorable toward N2 formation. However, achieving selective N2 production is kinetically challenged due to the underlying multistep mechanism involving bond cleavage and N-N bond formation. Herein, we report a high-entropy-driven kinetic steering strategy that accelerates the intrinsically favored "cyanate" pathway and couples it with selective NO2- reduction to achieve rapid urea-to-nitrogen conversion. A high-entropy oxide, CeMoCuFeCoOx (CMCFCO), steers UOR toward fast C-N cleavage and NO2- formation via entropy-induced site isolation. Coupled with a S-CuFe cathode in a flowing single-chamber membrane-free electrochemical cell (EC), the generated NO2- is selectively reduced to N2, preventing NO2- accumulation. Without iR compensation, CMCFCO delivers 300 mA cm-2 at 1.69 VRHE, and exhibits a pseudo-first-order rate constant of 0.068 min-1, 2.6-4.0 times higher than low-entropy oxides. S-CuFe reaches 1.48 A cm-2 at -1.3 VRHE. At 300 mA cm-2 in 1.5 M KOH + 0.33 M urea, 92.7% urea removal is achieved within 40 min with 93.8% Faradaic efficiency toward N2 products. In situ spectroscopy and DFT reveal that high-entropy-induced site isolation accelerates cyanate formation, while interfacial *N coupling on S-CuFe promotes selective N2 generation. This reaction-coupling framework reconciles kinetic accessibility with thermodynamic selectivity in UOR.