Promoting active hydrogen supply for kinetically matched tandem electrocatalytic nitrate reduction to ammonia

Electrocatalytic nitrate reduction (NORR) shows admirable potential for environmental remediation and producing valuable NH. However, the catalyst is restricted by the kinetic mismatch between NO-to-NO and NO-to-NH, which results in excess NO and poor NH selectivity. Herein, a kinetically matched tandem electrocatalytic strategy with tunable active hydrogen(*H) supply is designed. The combination of CuO and Co(HPO)(OH) (CoPO) playing key roles in NORR by i) on-demand supply of *H from CoPO; ii) the electronically coupled interface between CuO and CoPO enhance *H transfer kinetics. The CuO-CoPO-2 exhibits high NH yield of 22 mg cm h with Faradaic efficiency of 95 % at −0.37 V vs. RHE. In situ characterizations indicate the dynamic equilibrium between *H production and consumption contributes to high NORR performance. The techno-economic analyses reveal the system is economically viable compared to Haber-Bosch (H-B) process, which benefits from industrial current densities and superior energy efficiency at low potentials.