Concentrated photothermal-assisted CO2 reduction over NiO/ZnO p–n heterojunction nanoflower spheres

Photothermal-assisted photocatalysis, which couples localized thermal energy with photogenerated charge carriers to overcome thermodynamic and kinetic limitations, has emerged as an effective strategy for solar-driven CO2 reduction. Herein, nanoflower-like NiO/ZnO p–n heterojunction spheres were rationally constructed via a simple hydrothermal calcination method to achieve efficient concentrated photothermal-assisted CO2 reduction. The unique nanoflower morphology provides abundant interfacial contact between NiO and ZnO, while the formation of the p–n heterojunction establishes an internal electric field that suppresses electron-hole recombination. Under concentrated irradiation (4.31 W·cm−2), the photothermal coupling effect reduces the apparent activation energy and enables the NiO/ZnO photocatalyst to deliver CO and CH4 production rates of 51.78 and 15.96 μmol·g−1·h−1, which are 7.92 and 9.61 times higher, respectively, than those obtained under nonconcentrated illumination. Photoelectrochemical measurements and in situ DRIFTS further reveal that the built-in electric field facilitates directional charge transfer from ZnO to NiO, thereby promoting CO2 adsorption and activation. We demonstrate an efficient photothermal-coupling strategy to construct high-performance catalysts for artificial photosynthesis and solar-to-fuel conversion.