Promoting multielectron CO2 reduction using a direct Z-scheme WO3/ZnS photocatalyst

In this study, the WO 3 /ZnS Z-scheme-heterojunction photocatalyst was evaluated for the photocatalytic reduction of CO 2 in the presence of water vapor. The results demonstrated that the quantity of WO 3 (5–20 wt%) significantly affects the growth of crystallite size of ZnS, the modulation of the conduction band (CB) potential, and ultimately, the production of light hydrocarbons. The influences of temperature, volumetric flow, and WO 3 wt% in the heterostructured photocatalyst were analyzed in a continuous reaction system. The highest production rate of hydrocarbons at the lowest volumetric flow was achieved using a photocatalyst with 5 wt% WO 3 with respect to ZnS (W 5% Z), with propane (C 3 H 8 ) and propylene (C 3 H 6 ) as the main products. The observed effect was rationalized by the synergy between the crystallite size, CB potential, and formation of the heterojunction, which led to enhanced electron transfer on the active surface sites of the W 5% Z photocatalyst than on those of either ZnS or WO 3 . The remarkable performance of W 5% Z was attributed to the high production of charge carriers and their fast transfer from the direct Z-scheme photocatalyst surface to the reactants, which promoted the reduction of CO 2 molecules into C1-C3 hydrocarbons. The results indicate that the WO 3 /ZnS system is a good candidate for the chemical transformation of CO 2 into valuable products and must be considered for further studies. • A multielectron CO 2 reduction was achieved by using the direct Z-scheme WO 3 /ZnS photocatalyst. • Significant conversion of CO 2 to C 3 H 8 was attained at 80 °C and low volumetric flow rate. • The high activity of WO 3 /ZnS is due to improved transfer of charge carriers and surface features.