Tuning graphene for energy and environmental applications: Oxygen reduction reaction and greenhouse gas mitigation

Porous nitrogen-doped graphene samples were synthesized and tuned via pyrolysis of solid nitrogen precursor dimethyl-aminoterephthalate with graphene oxide as template. Our investigations show that the extent of thermal treatment, total concentration of nitrogen and the nature of nitrogen moieties play important roles in enhancing oxygen reduction reaction (ORR) and CO2 uptake. N-doped graphene synthesized at 650 °C (NG-650) with specific BET surface area of 278 m2/g, exhibits enhanced CO2 sorption capacity of 4.43 mmol/g (at 298 K, 1 bar) with exceptional selectivity (CO2:N2 = 42) and cyclic regeneration stability. In contrast, nitrogen-doped graphene synthesized at 750 °C (NG-750) demonstrated excellent catalytic activity for ORR via favourable 4e− transfer, performance stability with tests conducted up to 5000 cycles, and is unaffected by methanol cross-over effect. Thus, NG-750 shows potential to replace metal-based electrodes for fuel cell application. The comparative results for ORR with non-doped and nitrogen-doped graphene electrodes showed that graphitic nitrogen sites play vital role in enhancing catalytic activity.