Boosting Electrocatalytic Nitrate-to-Ammonia via Tuning of N-Intermediate Adsorption on a Zn-Cu Catalyst

The renewable-energy-powered electroreduction of nitrate (NO3-) to ammonia (NH3) has garnered significant interest as an eco-friendly and promising substitute for the Haber-Bosch process. However, the sluggish kinetics hinders its application at a large scale. Herein, we first calculated the N-containing species (*NO3 and *NO2) binding energy and the free energy of the hydrogen evolution reaction over Cu with different metal dopants, and it was shown that Zn was a promising candidate. Based on the theoretical study, we designed and synthesized Zn-doped Cu nanosheets, and the as-prepared catalysts demonstrated excellent performance in NO3--to-NH3. The maximum Faradaic efficiency (FE) of NH3 could reach 98.4 % with an outstanding yield rate of 5.8 mol g-1 h-1, which is among the best results up to date. The catalyst also had excellent cycling stability. Meanwhile, it also presented a FE exceeding 90 % across a wide potential range and NO3- concentration range. Detailed experimental and theoretical studies revealed that the Zn doping could modulate intermediates adsorption strength, enhance NO2- conversion, change the *NO adsorption configuration to a bridge adsorption, and decrease the energy barrier, leading to the excellent catalytic performance for NO3--to-NH3. Zn-doped Cu catalyst is used for electrocatalytic NO3- reduction. The Faradaic efficiency of NH3 can reach 98.4 % with a yield rate of 5.8 mol h-1 gcat.-1. The Zn dopants play a key role in modulating the adsorption strength of intermediates, enhancing the conversion of nitrite, altering the configuration of adsorbed *NO species to bridge adsorption, and reducing the energy barrier, leading to the high catalytic performance in NO3--to-NH3.image

Automated summary

Zn-doped Cu nanosheets were designed and synthesized for the electroreduction of NO3- to NH3. The catalyst showed excellent performance with a maximum Faradaic efficiency of 98.4% and a high yield rate of 5.8 mol g-1 h-1.