Tailoring the properties of g-C3N4 with CuO for enhanced photoelectrocatalytic CO2 reduction to methanol

In the present work, the physico-chemical and photoelectrocatalytic (PEC) carbon dioxide (CO2) reduction to methanol properties of graphitic carbon nitride (g-C3N4) were enhanced by the incorporation of CuO. The XRD, XPS, TEM, FESEM, UV-vis and photoluminescence (PL) spectroscopy techniques were used to characterize the synthesized g-C3N4 and CuO/g-C3N4 photocatalysts. The fabricated CuO/g-C3N4/carbon paper photocathode showed similar to 10.0 times enhanced photocurrent response and 5.3 times enhanced incident photon to current efficiency (IPCE) than the g-C3N4/carbon paper photocathode under CO2 atmosphere in aqueous NaHCO3 electrolyte solution on 470 nm light irradiation. The higher IPCE of CuO/g-C3N4/carbon paper photocathode was attributed to the higher absorption of the incident visible light which results in efficient electron (e(-)-hole (h(+)) pair generation and charge transfer for the PEC conversion of CO2. The production of methanol in aqueous phases was analysed and found to be 4.1 and 2.6 times higher by CuO/g-C3N4/carbon paper photocathode than g-C3N4/carbon paper and CuO/carbon paper photocathodes, respectively. The CuO/g-C3N4/carbon paper photocathode showed Faradaic efficiency and quantum efficiency of 75 % and 8.9 %, respectively for the production of methanol. The plausible mechanism for the production of methanol by CuO/g-C3N4/carbon paper photocathode by PEC reaction was also discussed.