Z-scheme CoAl-layered double hydroxide/indium vanadate heterojunction for enhanced and highly selective photocatalytic reduction of carbon dioxide to carbon monoxide

Development of efficient photocatalysts is essential for carbon dioxide (CO2) photocatalytic reduction. In this study, Z-scheme CoAl-layered double hydroxide (LDH)/indium vanadate (InVO4) heterojunction photocatalysts were synthesized using hydrothermal method, and their performance toward CO2 reduction and mechanism were determined. Results of characterizations showed that the CoAl-LDH/InVO4-30 exhibited desired morphology, the most efficient photogenerated carriers separation and charge transfer, and the highest photocurrent response. X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) manifested that charge transfer of the CoAl-LDH/InVO4 conformed to Z-scheme mechanism. The CoAl-LDH/InVO4-30 exhibited the highest carbon monoxide (CO) yield of 174.4 μmol g-1 within 2 h of reaction, which was 2.46 and 9.79 times of pure CoAl-LDH and InVO4, respectively. The CO selectivity was up to nearly 100%. Moreover, in-situ fourier transform infrared spectroscopy (ISFT-IR) demonstrated that bicarbonate (HCO3*) and carboxylate (COOH*) were the main intermediates during the CO2 reduction process, and possible CO2 reduction pathways were proposed. This work provides a reference for construction of Z-scheme LDH-based heterojunctions for efficient CO2 photoreduction.