Boosting Nitrate-to-Ammonia Conversion over Copper-Based Electrocatalysts by Facilitating Hydrogenation and Product Desorption

Abstract

Electrocatalytic nitrate reduction reaction (NitRR) in neutral condition offers a sustainable route for ammonia (NH₃) production and water purification. For the most extensively investigated Cu-based electrocatalysts that favor NO₃⁻ adsorption, insufficient hydrogenation capability and sluggish NH₃ desorption hinder the ultimate performance. Herein, we report Ca-doped Cu₂O co-modified by oxalate (Ca─Cu₂O─OA) as a novel and high-performance NitRR electrocatalyst. Experimental and theoretical results demonstrate that the Ca dopant with strong hydration effect facilitates the hydrogenation steps of adsorbed NO₃⁻ on the adjacent Cu active sites. The hydrogen-bonding interaction between OA and adsorbed NH₃ promotes the product desorption. Together with the strong NO₃⁻ adsorption capability and inhibited hydrogen evolution as a side reaction, excellent NitRR performance with a high Faraday efficiency (FE) of 97.49% and a high NH₃ yield of 15.02 mg h⁻¹ cm⁻² is achieved in neutral condition, outperforming most reported electrocatalysts. This work has provided new insights into the rational design of advanced NitRR electrocatalysts.