Exceptionally Durable CO₂ Photoreduction Mediated by Defect-Engineered CaIn₂S₄ Nanoflowers

Abstract

Solar-driven CO₂ reduction faces major limitations due to insufficient photoabsorption, delayed electron-hole separation, and a significant CO₂ activation barrier. Defect engineering was used to optimize these vital processes. As a prototype, typical nontoxic ternary sulfide CaIn₂S₄ (CIS) nanoflowers were designed, and abundant sulfur vacancies were deliberately created on their surfaces. The charge delocalization around the sulfur vacancies contributes to CO₂ conversion into the *COOH intermediate, which was confirmed by in situ Fourier-transform infrared spectroscopy. Ultrafast transient absorption spectroscopy manifests the sulfur vacancy that allows for a ∼1.3-fold increase in average recovery lifetime, confirmed by photoelectrochemical analysis and DFT calculations, which ensure promoted carrier separation rates. Consequently, the CISv demonstrates a CO rate of 10.95 μmol g⁻¹ h⁻¹, which is about 6.5 times greater than the pristine CIS nanoflowers, and its photocatalytic activity remains almost unchanged after 120 h of photocatalysis. Our findings will stimulate further research on vacancy-containing catalyst design for CO₂ reduction to hydrocarbons.

Keywords

charge transfer / CO₂ photoreduction / ternary sulfide / vacancy

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2025 The Author(s). EcoEnergy published by John Wiley & Sons Australia, Ltd on behalf of China Chemical Safety Association.