An efficient screening strategy towards multifunctional catalysts for the simultaneous electroreduction of NO₃⁻, NO₂⁻ and NO to NH₃

Multifunctional electrocatalysts that simultaneously reduce all NO_x species (NO₃⁻, NO₂⁻ and NO) to NH₃ can deliver superior efficiency compared with that for individual species. Herein, by using the first-principles method, an efficient strategy was proposed to screen NO_xRR multifunctional electrocatalysts, which focuses on the key protonation process of the essential NORR for the NO_xRR. Taking double-atom catalysts (DACs) with transition-metal dimer (M1/M2 = V, Cr, Mn, Fe, Co, Ni, and Cu) embedded N-doped graphene as examples, we showed that the proposed strategy was effective for electrocatalyst screening, and we identified Cu₂@NG as the best one, with rather low limiting potentials of −0.36, −0.32, and −0.30 V for the NO₃RR, NO₂RR, and NORR, respectively. Furthermore, a simple descriptor for evaluating electrocatalytic activity was established. And the physical mechanism in terms of the electronic structures was analyzed for the Cu₂ DAC case in view of NO activation. Finally, from the screening test in some 4d and 5d late transition-metal based DACs, the proposed strategy was confirmed to be feasible to find another NO_xRR multifunctional electrocatalyst. Our work provides a procedure for efficiently screening multifunctional electrocatalysts to simultaneously reduce all NO_x species to synthesize NH₃ and sheds light on the atomic mechanisms for NO_x electroreduction as well.