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

Abstract

Here, we describe the fabrication of surface oxygen vacancy-enriched ZnFe₂O₄@TiO₂ double-shell hollow heterostructure nanospheres (ZnFe₂O₄@H-TiO_2-x) coupled with spatially separated CoO_x 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 CoO_x/ZnFe₂O₄/Au-Cu and ZnFe₂O₄@H-TiO_2-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.

Keywords: Dual cocatalysts; Heterojunction; Hollow dual-shell nanosphere; Photocatalytic CO(2) reduction.