Computational Screening of High Activity and Selectivity TM/g-C 3 N 4 Single-Atom Catalysts for Electrocatalytic Reduction of Nitrates to Ammonia.

Electrocatalytic reduction of nitrates (NO ₃ RR) selectively generating ammonia (NH ₃ ) opens up a new idea for treating nitrates in wastewater, which not only reduces nitrates but also obtains the valuable product ammonia. By first-principles calculations, we explore the activity and selectivity for NO ₃ RR to NH ₃ of TM/g-C ₃ N ₄ single-atom catalysts. Six TM/g-C ₃ N ₄ catalysts (TM = Ti, Os, Ru, Cr, Mn, and Pt) are selected by a four-step screening method. Ru/g-C ₃ N ₄ is the most promising of these six TM/g-C ₃ N ₄ catalysts because of its lowest energy barrier and extraordinary selectivity. The origin of the NO ₃ RR activity of Ru/g-C ₃ N ₄ is explained from the viewpoint of NO ₃ ^- adsorption. In addition, the hydrogen evolution reaction has also been implied to be uncompetitive for the poor adsorption on H atoms. This work provides a screening mechanism for finding new catalysts for NO ₃ RR to NH ₃ , promotes the development of NO ₃ RR, and provides a stimulating impetus for further experimental exploration.