Theoretical insights into oxygen reduction reaction catalyzed by phosphorus-doped divacancy C3N nanosheet.

The catalytic reduction of O2 molecule into H2O is investigated over a P-doped divacancy C3N nanosheet (P-Dv-C3N) by using density functional theory calculations. A negative formation energy is calculated for P-Dv-C3N, suggesting that the introduction of a P atom into divacancy defective C3N would be thermodynamically favorable. The oxygen reduction reaction (ORR) over P-Dv-C3N would proceed via a 4e- pathway (O2 + 4H+ + 4e-→ 2H2O) at room temperature. The rate-determining step of the ORR on P-Dv-C3N is O + H+ + e- → OH which requires an activation energy of 1.21 eV. These results provide helpful insights into design novel metal-free catalysts to improve the kinetics of ORR in fuel cells.