Photocatalytic reduction of <scp>CO2</scp> to methanol over <scp>ZnFe2O4</scp>/<scp>TiO2</scp> (p–n) heterojunctions under visible light irradiation

AbstractBACKGROUNDThe development of visible light photocatalysts for CO2 reduction into methanol is a challenge, as most of the reported photocatalysts can only work in a UV light environment. Slow kinetics and poor selectivity of CO2 towards methanol are currently two significant drawbacks limiting the practical application of CO2 reduction into methanol.RESULTSA ZnFe2O4/TiO2 heterojunction with a ratio of unity was found to lead to the highest methanol yield of 693.31 μmol (g cat)−1 under a light intensity of 100 mW cm−2. This photocatalyst also possessed the highest BET surface area of 6.5211 m2 g−1 and better morphological structure, as compared with other ratios (1:2, 2:1 w/w). Interestingly, a loading of 1 g L−1 of ZnFe2O4/TiO2 (1:1) heterojunction photocatalyst in the pre‐annealing treatment of ZnFe2O4 at 900 °C and post‐annealing treatment of ZnFe2O4/TiO2 (1:1) composite at 500 °C revealed that there was an enhancement in the interfacial interaction, and subsequently an efficient photoreduction of CO2 into methanol.CONCLUSIONSThis study demonstrates facile fabrication of p–n heterostructured phototcatalysts for reduction of CO2 with marked improvement in methanol yield under visible light irradiation. It provides a viable route for exploring the effects of composition, hydrothermal treatment, and pre‐/post‐annealing treatment of hybrid semiconductor composites used to scale up photocatalytic CO2 conversion in solar fuel‐based devices.

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