Rational design of bifunctional OER/ORR metal-free catalysts based on boron-doped graphene by strain engineering

Designing high-activity and durable bifunctional catalysts for the oxygen reduction reaction and oxygen evolution reaction is crucial for advancing fuel cells. However, the development of electrocatalysts is usually based on transition metal materials in previous literature. Herein, we explore a group of single boron atoms doped on graphene with different N coordinations as promising bifunctional OER/ORR metal-free catalysts by density functional theory calculations. By constructing a volcano-shaped relationship between the OER/ORR activity and both Δ<i>E</i>_*O and Bader charge (<i>δ</i>), the B-C₂N structure is identified as a superior catalyst, with an overpotential of 0.38 V and 0.36 V for the OER and ORR, respectively. Although the thermodynamic barrier of the ORR is lower than that of the ORR in the same catalyst, the reaction rate of the ORR is only one-hundred-and-fiftieth that of the OER. Moreover, the catalytic activity is further enhanced in the presence of tensile strain, which can be attributed to the shift of the p-band center and charge accumulation.