Redirecting surface reconstruction of CoP-Cu heterojunction to promote ammonia synthesis at industrial-level current density

The electrochemical reduction of nitrate (NO₃⁻RR) represents a compelling approach for the treatment of wastewater, serving as both a sustainable substitute to the energy-intensive Haber-Bosch process and a viable alternative to direct electroreduction of N₂. However, the process involves multiple electron and proton transfer steps and a complex reaction pathway, leading to low Faraday efficiency and selectivity. Herein, we demonstrated a directional surface reconstruction to generate CoP-Cu/Co(OH)₂ heterojunction for synergistic catalysis of NO₃⁻RR. Impressively, a high ammonia generation rate of 9.91 mmol h⁻¹cm⁻² and a Faraday efficiency of 99.2 % can be achieved at an industrial-relevant current density of 2 A cm⁻². Moreover, the catalyst exhibited exceptional durability, maintaining the activity for 110 h under industrial current density. Such outstanding NO₃⁻RR performance can be ascribed to the synergistic catalytic effect among the active sites of Cu, CoP and Co(OH)₂, as well as the excellent stability of self-supported catalyst. Specifically, Cu and CoP sites synergistically promote the conversion of NO₃⁻ to NO₂⁻ and NO₂⁻ to NH₃. Meanwhile, the partial reconstructed Co(OH)₂ from CoP enhances water dissociation, thereby supplying active hydrogen (*H) essential for NO₃⁻RR. When applied to a membrane electrode assembly (MEA) system, CoP-Cu/Co(OH)₂ can deliver satisfactory ammonia production rate with appreciable economic benefits at industrial-level current densities, highlighting its potential for industrial applications.