Dual p-block atoms anchored on N-doped graphene: Efficient transition-metal-free catalysts for nitrate reduction to ammonia

• All the catalysts are thermodynamically stable and electrochemically favourable, with great potential for experimental synthesis. • NO 3 - is strongly adsorbed and activated on the catalyst surfaces. • BAl@N 6 -G, BIn@N 6 -G, AlGa@N 6 -G, AlIn@N 6 -G, GaGa@N 6 -G and GaIn@N 6 -G possess low limiting potentials of -0.50, -0.25, -0.47, -0.23, -0.38, and -0.18 V, respectively. • HER and undesired NO2, NO, N2 and N2O reduction can be suppressed. Nitrate reduction reaction (NO 3 RR) is an efficient strategy to mitigate the nitrate-induced pollution and generate high-value product as a substitute for Haber-Bosch process. However, this process face challenges due to the lack of effective electrocatalysts and the limited understanding of the mechanism that drives NO 3 RR. Owing to more active sites, high selectivity and stability, double atom catalysts (DACs) outperform the single-atom counterparts. Herein, the catalytic performance of double p -block atoms embedded in nitrogen-doped graphene for the nitrate reduction reaction is investigated using density functional theory (DFT). A four-step screening process were conducted to evaluate stability, NO 3 - adsorption strength, selectivity and catalytic efficiency. Among the 10 candidates, BAl, BIn, AlGa, AlIn, GaGa and GaIn@N 6 -G stood out with low limiting potentials of -0.50, -0.25, -0.47, -0.23, -0.38, and -0.18 V, respectively. Furthermore, the hydrogen evolution reaction, and the formation of the by-products were effectively inhibited due to high energy barrier, validating outstanding selectivity. This study provides a fundamental insight into screening efficient novel catalysts and offers the theoretical guidance for the experimental design of the transition-metal free DACs for NO 3 RR.