Direct Z‑Scheme WO3/Graphitic Carbon Nitride Nanocomposites for the Photoreduction of CO2

In this article, we successfully prepared the WO3/g-C3N4 (WO/CN) heterojunction photocatalyst with high photocatalytic CO2 reduction performance by the simple impregnation–calcination process. Transmission electron microscopy (TEM) analysis shows that the WO3 nanoparticles (WO3 NPs) are successfully attached to the g-C3N4 nanosheets (CN). UV–vis reflectance spectrum (UV–vis DRS), photoluminescence spectrum (PL), and photoelectrochemical (PEC) results confirm that the building of a WO/CN heterojunction is beneficial to the transfer and separation processes of the photogenerated carriers in the photocatalysts. The photoreduction performances of the obtained samples are indicated by the photocatalytic CO2 reduction process under UV and visible light irradiation. These experiments prove that the 10-WO/CN photocatalyst has the best photoreduction performance compared to other obtained photocatalysts. The yields of CO and CH4 in the presence of the 10-WO/CN photocatalyst are 8.9 and 47.7 times larger than those of pure CN under UV irradiation. For the irradiation of visible light, the yield rates of CO and CH4 over 10-WO/CN are 8.6 and 7.5 times greater than those of the CN. On the basis of these photocatalytic results and electron spin resonance (ESR) results, the possible direct Z-scheme electron transfer mechanism for 10-WO/CN with the improved photoreduction CO2 activity has been discussed.