Improved charge separation and carbon dioxide photoreduction performance of surface oxygen vacancy-enriched zinc ferrite@titanium dioxide hollow nanospheres with spatially separated cocatalysts

ZnFe2O4@H-TiO2-x double-shell hollow heterostructure nanospheres anchored with spatially separated CoOx and Au-Cu dual cocatalysts were fabricated. The unique hollow spherical heterostructure and the produced surface oxygen vacancies further enhance visible light utilization and CO2 adsorption/activation ability. [Display omitted] •Double-shell hollow nanospheres with spatially separated cocatalysts are fabricated.•ZnFe2O4@H-TiO2-x heterostructure accelerate the transfer and separation of charges.•Electrons and holes can be trapped and separated by corresponding cocatalysts.•Au-Cu bimetalic cocatalyst can improve the yield and selectivity of CO2 photoreduction. Here, we describe the fabrication of surface oxygen vacancy-enriched ZnFe2O4@TiO2 double-shell hollow heterostructure nanospheres (ZnFe2O4@H-TiO2-x) coupled with spatially separated CoOx and Au-Cu bimetallic cocatalysts. The ZnFe2O4@TiO2 heterojunction and spatially separated dual cocatalysts can significantly promote the separation of photoinduced charge carriers. Combined with the unique hollow double-shell heterostructure characteristics and improved surface state properties, the hybrid nanospheres can efficiently adsorb and activate CO2 molecules. These advantages cause the optimized catalyst to exhibit remarkably higher gas-phase photocatalytic CO2 reduction activity than the control CoOx/ZnFe2O4/Au-Cu and ZnFe2O4@H-TiO2-x double-shell hollow nanospheres loaded with a single cocatalyst. Meanwhile, the Au-Cu bimetal effect boosts the CO2 conversion rate and CH4 selectivity. The optimized hybrid catalyst with a Au/Cu ratio of 1:1 provides a CH4 yield of 21.39 μmol g−1 h−1 with 93.8% selectivity. This work provides a rational photocatalyst design to improve CO2 conversion and CH4 selectivity.