Oxygen reduction reactions from boron-doped graphene quantum dot catalyst electrodes in acidic and alkaline electrolytes

Abstract

Background: Boron- and nitrogen-codoped graphene quantum dots (GQDs) were synthesized and served as metal-free electrocatalyst for oxygen reduction reaction (ORR) in acidic and alkaline electrolytes. Methods: The GQD catalysts were prepared using an efficient solvothermal technique based on the pyrolysis of 1,3,6-trinitropyrene and boric acid at 180°C for 12 h. The as-prepared GQDs with an average particle size of ∼4 nm contain a high B/C and N/C level (B/C and N/C atomic ratio: 14.6 and 6.5 at.%) with a large amount of O-rich functionalities. Significant Findings: The B- and N-codoped GQD catalytic electrodes provide ultra-high electrochemically active surface area for ORR with exceptional durability. Indeed, the ORR catalytic activity in both acidic and alkaline electrolytes is significantly enhanced via B- and N-doping into the GQDs lattices. Highly improved ORR activity was majorly due to the synergistic effect of the B- and N-codoped GQD catalysts, where the N functionalities facilitate the formation of C*–O2(ads) sites, whereas the B dopants regenerate the occupied and poisoned sites for the subsequent catalytic cycle. The solvothermal synthesis technique developed in this study sets the stage for developing high-performance metal-free catalytic nanomaterials for ORR.