Rational design of bifunctional ORR/OER catalysts based on Pt/Pd-doped Nb2CT2 MXene by first-principles calculations

Abstract

Developing highly active, stable, and conductive bifunctional oxygen reduction (ORR) and oxygen evolution (OER) catalysts is a key step for fuel cells and metal–air batteries. Herein, an effective idea for designing bifunctional catalysts is presented by regulating the surface electronic structures of Nb₂CT₂ (T = O, F, and OH) using Pt/Pd single atoms. The results indicated that Pt-doped systems (Nb₂CO₂–V_O–Pt, Nb₂CF₂–V_F–Pt) were the most promising bifunctional ORR/OER catalysts. In particular, Nb₂CF₂–V_F–Pt was even better than landmark Pt(111) and IrO₂(110) catalysts, with relatively low overpotentials of 0.40 V and 0.37 V for ORR and OER, respectively. The high catalytic nature of Nb₂CF₂–V_F–Pt was explained by electronic structures, volcano plots, and charge transfer mechanisms, which mainly depended on the electron donor capacity and synergistic effects from F-terminated groups and Pt noble metals. Moreover, 100% utilization of Pt was achieved for the designed bifunctional catalysts with a minimum radius between two adjacent active centers. This was the first design of a bifunctional ORR/OER catalyst based on Nb₂CT₂ and highlighted a new perspective on the application of MXenes.