Rational design of efficient silver-based homonuclear dual-atom alloys for electrochemical nitrate reduction to ammonia via first-principles calculation and machine learning

Abstract

Electrochemical nitrate reduction reaction (eNO₃RR) offers a promising route for simultaneous NO₃⁻ remediation and sustainable ammonia (NH₃) production, yet its practical application is hindered by the lack of efficient and stable electrocatalysts. Herein, we systematically investigate a series of homonuclear dual-atom alloy (DAA) catalysts by embedding transition-metal (TM) dimers into an inert Ag (111) surface using density functional theory calculations. Among these candidates, Ru₂Ag and Os₂Ag exhibit outstanding eNO₃RR activity, with low limiting potentials of −0.37 and −0.21 V, respectively, together with high NH₃ selectivity and favorable formation feasibility. Constant-potential thermodynamic simulations further demonstrate their robust catalytic performance across different pH levels and applied potentials. Moreover, constant-potential slow-growth simulations based on equilibrated AIMD configurations reveal a low kinetic barrier for the potential-determining *NO hydrogenation step on representative Os₂Ag under acidic conditions. Electronic structure analyses reveal that the embedded TM dimers induce pronounced local charge redistribution and electron enrichment at the active sites. This modulation facilitates electron injection into the antibonding orbitals of *NO₃, thereby promoting *NO₃ activation through an “acceptance-donation” mechanism. Furthermore, by integrating Pearson correlation analysis with the Sure Independence Screening and Sparsifying Operator (SISSO) method, we identify a two-dimensional descriptor based on the cohesive energy and valence electron number of the TM species. Within the present dataset of Ag-based homonuclear DAAs, this descriptor captures the electron-energy coupling associated with eNO₃RR activity. Nevertheless, its universality to heteronuclear DAAs, other host metals, or different reaction environments remains to be further validated. These findings offer mechanistic insights into electronic-structure modulation in DAA catalysts and provide a focused theoretical basis for the rational exploration of Ag-based DAA catalysts for eNO₃RR to NH₃.