Photocatalytic reduction of <scp>CO<sub>2</sub></scp> to methanol over <scp>ZnFe<sub>2</sub>O<sub>4</sub></scp>/<scp>TiO<sub>2</sub></scp> (p–n) heterojunctions under visible light irradiation
Farukh Iqbal, Asad Mumtaz, Syed Shahabuddin, M.I. Abdul Mutalib, Maizatul Shima Shaharun, Trinh Duy Nguyen, Md. Maksudur Rahman Khan, Bawadi Abdullah
Abstract
Abstract BACKGROUND The development of visible light photocatalysts for CO 2 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 CO 2 towards methanol are currently two significant drawbacks limiting the practical application of CO 2 reduction into methanol. RESULTS A ZnFe 2 O 4 /TiO 2 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 m 2 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 ZnFe 2 O 4 /TiO 2 (1:1) heterojunction photocatalyst in the pre‐annealing treatment of ZnFe 2 O 4 at 900 °C and post‐annealing treatment of ZnFe 2 O 4 /TiO 2 (1:1) composite at 500 °C revealed that there was an enhancement in the interfacial interaction, and subsequently an efficient photoreduction of CO 2 into methanol. CONCLUSIONS This study demonstrates facile fabrication of p–n heterostructured phototcatalysts for reduction of CO 2 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 CO 2 conversion in solar fuel‐based devices.