Enhanced photocatalytic CO2 valorization over TiO2 hollow microspheres by synergetic surface tailoring and Au decoration

Abstract

The photocatalytic reduction of CO₂ with H₂O into valuable solar fuels is a sustainable solution for addressing the fossil energy crisis and mitigating the greenhouse effect. The exploitation of an efficient TiO₂ photocatalyst for photocatalytic CO₂ reduction is still urgently desirable but quite challenging. In this work, highly porous fluorinated TiO₂ hollow microspheres with abundant exposed {001} facets and abundant surface defects (including Ti³⁺ and oxygen vacancies (V_o)) were fabricated via a fluoride-mediated self-transformation pathway, which were then decorated with multifunctional Au nanoparticles via in situ photochemical deposition. The photocatalytic CO₂ reduction activity and selectivity were significantly enhanced over the as-prepared Au-modified TiO₂ hollow microspheres under both full-spectrum and visible light illumination, because of the multiple synergetic effects of host–guest modifications in tuning light harvesting, charge separation, and CO₂ adsorption and activation. First, the light harvesting capacity was enhanced because of the light trapping effect of hollow cavities together with the surface plasmon resonance (SPR) effect of surface decorated Au nanoparticles. Second, the charge transfer efficiency was significantly enhanced by simultaneously introducing {001}/{101} facet junctions and introducing Au/TiO₂ Schottky junctions. In addition, surface CO₂ adsorption and activation were enhanced owing to the strong affinity of decorated Au nanoparticles to CO₂ molecules and abundant surface Ti³⁺ and V_o defect sites, significantly dominating the photocatalytic CO₂ reduction reaction dynamics and pathway. This study not only demonstrates that synergetic host–guest engineering is a novel feasible avenue to design high-performance photocatalysts for photocatalytic CO₂ reduction, but also offers new insights into integrated tuning of multiple photocatalytic processes.