Effect of nonmetals (B, O, P, and S) doped with porous g-C3N4 for improved electron transfer towards photocatalytic CO2 reduction with water into CH4

Photocatalytic conversion of carbon dioxide (CO2) into gaseous hydrocarbon fuels is an auspicious way to produce renewable fuels in addition to greenhouse gas emission mitigation. In this work, non-metals (B, O, P, and S) doped graphitic carbon nitride (g-C3N4) was prepared via solid-state polycondensation of urea for photocatalytic CO2 reduction into highly needed methane (CH4) with water under UV light irradiation. The various physicochemical characterization results reveal the successful incorporation of B, O, P, and S elements in the g-C3N4 matrix. The maximum CH4 yield of 55.10 nmol/(mLH2O.gcat) over S-doped g-C3N4 has been obtained for CO2 reduction after 7 h of irradiation. This amount of CH4 production was 1.9, 1.4, 1.7, and 2.4-folds higher than B, O, P and bare g-C3N4 samples. The doping of S did not enlarge the surface area and photon absorption ability of the g-C3N4 sample, but this significant improvement was evidently due to effective charge separation and migration. The observed results imply that the doping of non-metal elements provides improved charge separation and is an effective way to boost photocatalyst performance. This work offers an auspicious approach to design non-metal doped g-C3N4 photocatalysts for renewable fuel production and would be promising for other energy application.