Unraveling the Performance Descriptors for Designing Single‐Atom Catalysts on Defective MXenes for Exclusive Nitrate‐To‐Ammonia Electrocatalytic Upcycling

Abstract

AbstractElectrocatalytic nitrate reduction reaction (NO3RR) is a promising approach for converting nitrate into environmentally benign or even value‐added products such as ammonia (NH3) using renewable electricity. However, the poor understanding of the catalytic mechanism on metal‐based surface catalysts hinders the development of high‐performance NO3RR catalysts. In this study, the NO3RR mechanism of single‐atom catalysts (SACs) is systematically explored by constructing single transition metal atoms supported on MXene with oxygen vacancies (Ov‐MXene) using density functional theory (DFT) calculations. The results indicate that Ag/Ov‐MXene (for precious metal) and Cu/Ov‐MXene (for non‐precious metal) are highly efficient SACs for NO3RR toward NH3, with low limiting potentials of −0.24 and −0.34 V, respectively. Furthermore, these catalysts show excellent selectivity toward ammonia due to the high energy barriers associated to the formation of byproducts such as NO2, NO, N2O, and N2 on Ag/Ov‐MXene and Cu/Ov‐MXene, effectively suppressing the competitive hydrogen evolution reaction (HER). The findings not only offer new strategies for promoting NH3 production by MXene‐based SACs electrocatalysts under ambient conditions but also provide insights for the development of next‐generation NO3RR electrocatalysts.