Performance analysis of rGO-bridged g-C₃N₄/ZnV₂O₆ S-scheme heterojunction for CO₂ photoreduction with H₂O in an externally reflected photoreactor

The photocatalytic conversion of CO₂ with H₂O over rGO-bridged g-C₃N₄/ZnV₂O₆ S-scheme heterojunction using an externally reflected photoreactor has been investigated. The structure and properties of photocatalysts, prepared via the one-pot solvothermal method, were characterized by XRD, RAMAN, FESEM, EDX, HRTEM, UV–vis and PL spectrophotometry. The 4 % rGO-bridged g-C₃N₄/ZnV₂O₆ (1:1) nanocomposite registered the highest CH₃OH yield. The maximum yield of CH₃OH over 4 % rGO-bridged g-C₃N₄/ZnV₂O₆ (1:1) nanocomposite was 6246.1 μmol/g-cat; 1.34 and 1.51 folds higher than g-C₃N₄/ZnV₂O₆ (1:1) and ZnV₂O₆ photocatalysts, respectively. Significant enhancement in quantum efficiency of an externally reflected photoreactor over 4 % rGO-bridged g-C₃N₄/ZnV₂O₆ (1:1) nanocomposite was observed compared to the slurry photoreactor. This is obviously because of the greater mobility of charges with hindered recombination rate and higher photonic efficiency. The stability of 4 % rGO-bridged g-C₃N₄/ZnV₂O₆ (1:1) nanocomposite was partially reduced after several cyclic runs. It is believed that the photocatalyst consisting of three components has demonstrated improved photocatalytic activity through a S-scheme mechanism, utilizing rGO as an electron mediator to enhance the overall performance of the S-scheme heterojunction.