Rational design of Bifunctional OER/ORR Metal-free Catalysts based on Boron-doped Graphene by Strain Engineering

Abstract

Designing high-activity and durability bifunctional oxygen reduction and oxygen evolution reduction catalysts is an important factor for 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 coordination as promising bifunctional OER/ORR metal-free catalysts by density functional theory calculations. By constructing the volcano-shaped relationship between the OER/ORR activity with 𝛥E*O and Bader charge, the B-C2N structure is identified as a superior catalyst, with an overpotential of 0.38 eV and 0.36 eV for OER and ORR, respectively. Although the thermodynamic barrier of ORR is lower than the ORR in the same catalyst, the reaction rate of ORR is only one hundred and fifty of 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 charger accumulation.