Theoretical study of Cu-IIIA binary alloy catalysts for electrochemical nitrate reduction to ammonia

Abstract

Electrocatalytic reduction of nitrate to ammonia (NO₃RR) has emerged as a promising approach for wastewater purification and NH₃ electrosynthesis. Unfortunately, the catalytic performance of electrocatalysts is hindered by poor activity and selectivity for practical applications. Herein, three types of Cu-based alloys, composed of post-transition metals (Al, Ga and In), were investigated for the NO₃RR process. Using density functional theory (DFT) calculations, the reaction pathways for three catalysts along with Gibbs free energy evolution were identified, where enhanced activity was observed in the sequence of Al, Ga and In with limiting potentials of −0.77 V, −0.21 V and −0.18 V, respectively. The favourable nitrate reduction is due to enhanced electronic distribution and conductivity. The relationship between nitrate adsorption and limiting potential demonstrated that moderate nitrate adsorption is associated with higher activity. In addition, the proton adsorption and by-product formation (N₂O) on Ga₂Cu(100) was found to be difficult, and Ga₂Cu is identified as a highly efficient alloy catalyst for the e-NO₃RR. Cu-based bimetallic systems with excellent NO₃RR performance were proposed as promising candidates, thus providing insights into the rational design of novel catalytic materials through the p-block alloying strategy.