Reduced Cu/Pt–HCa₂Ta₃O₁₀ Perovskite Nanosheets for Sunlight‐Driven Conversion of CO₂ into Valuable Fuels

Reduced perovskite HCa₂Ta₃O₁₀ nanosheets loaded with Pt and Cu are synthesized for sunlight‐driven conversion of CO₂ with water vapor into valuable fuels. Perovskite nanosheets are prepared by exfoliating layered perovskite CsCa₂Ta₃O₁₀ via tetra butyl ammonium ion exchange, followed by liquid ultrasonic exfoliation. The obtained nanosheets exhibits a high specific surface area (>200 m² g⁻¹). The photocatalytic performance of the resulting reduced perovskite nanosheets is evaluated for CO₂ photoreduction under sunlight in the presence of saturated water vapor. The reduced nanosheets exhibit much higher photoactivity than the nonreduced ones. This can be ascribed to their unique structure. The hydrogen treatment in the presence of platinum induces a considerable amount of Ta⁺⁴ and oxygen vacancies, which apparently improves the visible light absorption of perovskite nanosheets. Moreover, the introduction of CuO nanoparticles significantly improves the electron–hole separation through the formation of a p–n junction. It also enhances the adsorption of CO₂ and stabilizes C1 intermediates which are favorable for CC coupling to form C2 products (e.g., ethanol). The formation rates of ethanol and methanol are 113 and 7.4 µmol g⁻¹ h⁻¹, respectively, while only methanol is obtained at the rate of 125.9 µmol g⁻¹ h⁻¹ in the absence of CuO nanoparticles.