Enhanced CO2 Photoreduction by Ni(OH)2‐x/WO3 Nanofibers with Efficient CO2 Activation and Charge Separation

Abstract Electrospun WO 3 nanofibers show great potential in solar‐powered CO 2 reduction, but they still suffer from rapid charge recombination and difficult CO 2 activation. Here, WO 3 nanofibers are modified by in situ growth of freestanding oxygen‐vacancy Ni(OH) 2‐ x nanosheets, and explored their charge separation and CO 2 reduction mechanisms by using in situ characterization techniques and density functional theory (DFT) calculations. Some electrons of Ni(OH) 2‐ x transferred to WO 3 nanofibers upon hybridization owing to their remarkable different work function, which induces a built‐in electric field (BIEF) at interfaces with directions pointing from Ni(OH) 2‐ x to WO 3 . Driven by the electric field, the photogenerated electrons flow to Ni(OH) 2‐ x , while the holes remain at WO 3 , achieving spatial charge separation. Further, CO 2 adsorbed on Ni(OH) 2‐ x shows apparent molecular activation, as suggested by its bent and elongated OCO bonds. The Ni(OH) 2‐ x /WO 3 nanofibers exhibit an enhanced CO production rate with respect to WO 3 (54.4 vs 8.1 µmol g −1 h −1 ). The 13 CO 2 isotope tracing experiment confirms that the CO product originated from the input CO 2 . This work may inspire the development of more advanced photocatalysts for CO 2 activation and photoreduction by defect engineering.