N-doped vertical graphene arrays/carbon quantum dots derived from vinegar residue as efficient water-splitting catalyst in a wide pH range

Tailoring vinegar residue-derived all-carbon electrodes for efficient electrocatalytic carbon dioxide reduction to formate through heteroatom doping and defect enrichment

Electrocatalytic carbon dioxide reduction (ECO2R) to formate is the most technically and economically feasible approach to achieve electrochemical CO2 value addition. Here, a few-layer graphene is prepared from vinegar residue. Then a series of heteroatom-doped vertical graphene electrodes (X-rGO, X=P/S/N/B/, NS/NP/NB, NSP/NSB/NPB/NSPB) are prepared. The NS-rGO has improved ECO2R to formate selectivity (Faraday Efficiency (FEHCOO-) = 78.7 %) thanks to the synergistic effect between N and S. Carbon quantum dots (CQDs) are introduced into the electrode, the doped heteroatoms are further removed by high-temperature to form the defects-rich electrode (NS-CQDs-rGO-1100), which has better catalytic performance (FEHCOO-=90 %, stability over 10 h) with electrochemical double layer capacitance of 12.5 mF cm-2. The intrinsic effect of heteroatom doping and defects on the ECO2R activity of the electrodes are explored by density functional theory calculation. This work broadens the field of preparation of graphene and opens the door to the development of cost-effective electrocatalysts for efficient ECO2R.