“…In this regard, the development of catalysts for NRA is of great value. Many metallic catalysts with appreciable catalytic activity, such as Cu, Fe, Co, Ni, Bi, Ru, Ag, Pt, and Pd, have been developed to catalyze the electroreduction of nitrate. − Among them, Pd has fast NO 3 – reduction kinetics due to a lower *NO 3 dissociation barrier. , Meanwhile, PdO could serve as an active center for the adsorption of hydrogen species by surface oxygen atoms with a high adsorption energy (−3.22 eV). , Therefore, the combination of Pd and PdO can promote the selective hydrogenation of nitrate to ammonia. − In addition, increasing oxygen vacancies in metal oxide-based catalysts can adsorb nitrates, weaken the oxygen–nitrogen bond, and prevent the formation of by-products. , …”