Theoretical prediction of efficient Cu-based dual-atom alloy catalysts for electrocatalytic nitrate reduction to ammonia via high-throughput first-principles calculations

Abstract

The electrocatalytic nitrate (NO₃⁻) reduction reaction (eNO₃RR) to produce valuable ammonia (NH₃) is a promising strategy for achieving wastewater treatment and energy conversion. Very recently, dual-atom alloy (DAA) catalysts, featuring active metal dimers embedded in the surface of an inert host metal, have garnered initial research interests owing to the unique geometric and electronic structures of the active metal dimers. The Cu(111) surface shows promising eNO₃RR performance, but it still suffers from insufficient activity and selectivity. Herein, stimulated by the concept of DAA, we extensively investigated the potential of Cu-based homonuclear DAAs (TM₂Cu, TM = 3d, 4d, 5d) for eNO₃RR through high-throughput first-principles calculations. The Mn₂Cu, Fe₂Cu, and Co₂Cu DAAs are found to have excellent eNO₃RR performance with lower limiting potentials (U_L) of −0.18, −0.30, and −0.28 V, respectively, as well as enhanced selectivity, compared with the pristine Cu(111) (U_L = −0.38 V). The influence of pH and applied potential was further investigated using constant-potential density functional theory (DFT) calculations. Notably, compared to Cu(111), the Mn₂Cu and Co₂Cu DAAs demonstrate superior activity and selectivity under varying applied potentials and pH conditions. The origin of the activity is attributed to the charge “acceptance–donation” mechanism, which results in continuous d–σ and d–π* interactions between the TM dimer and *NO₃, leading to more bonding states near the E_f, and thus stimulating the adsorption and activation of NO₃⁻. The selective enhancement of TM₂Cu is due to the fact that NO₃⁻ gains more electrons from TM dimers compared to H atoms, which helps inhibit the HER. This work not only proposes a new approach for the rational design of efficient eNO₃RR catalysts for NH₃ production by regulating metal active centers, but also provides in-depth insights into the underlying mechanism for the enhanced performance of DAA catalysts.