Theoretical exploration of a single-atom catalyst anchored on β ₁₂ -borophene for electrochemical nitrate reduction: catalyst screening and mechanistic insight

The electrochemical nitrate reduction reaction (NO₃RR) presents a viable approach for mitigating nitrate pollution and serves as a promising alternative for low-temperature ammonia synthesis, potentially replacing the traditional Haber-Bosch process. However, the development of high-performance NO₃RR catalysts is impeded by a limited understanding of the catalytic mechanisms involved in metal-based surface catalysts. In this study, we employed density functional theory (DFT) to explore the catalytic potential of various single metal atoms anchored on β₁₂ borophene (denoted as M@β₁₂) for NO₃RR leading to ammonia production. Through extensive computational screening and systematic assessment of the activity and selectivity of different M@β₁₂ candidates, Mn@β₁₂ was identified as a highly efficient single-atom catalyst for NO₃RR, exhibiting a low limiting potential of -0.33 V. Furthermore, Mn@β₁₂ effectively suppresses the competitive hydrogen evolution reaction and the formation of undesired by-products, including NO₂, NO and N₂. We further rationalized the superior catalytic performance of Mn@β₁₂ by analyzing the adsorption strengths of key intermediates associated with the potential-determining step (PDS) as a descriptor. Our findings not only provide novel strategies for enhancing ammonia production <i>via</i> M@β₁₂ electrocatalysts under ambient conditions but also contribute to a deeper understanding of the NO₃RR mechanism.