An assembled ternary photocatalyst CoPh/CdSe@TiO2 for simultaneous photocatalytic CO2 and proton reduction

Abstract

The utilization of solar energy to produce solar fuels, namely hydrogen (H₂) and carbon-based fuels, represents a sustainable and clean method for fuel production. The state-of-the-art photocatalysts realized H₂ production or CO₂ reduction, separately, with high activity and stability. Syngas, a gaseous mixture of carbon monoxide (CO) and H₂ is an important feedstock in petrochemical industries. Syngas with a reasonable CO : H₂ ratio satisfies different product requirements in Fischer–Tropsch (F–T) synthesis. The production of syngas via photocatalysis through protons and CO₂ reduction reactions is a promising strategy to obtain syngas through solar-to-chemical energy conversion. Herein, we report a novel ternary photocatalyst, CoPh/CdSe@TiO₂, by assembling a molecular CO₂ reduction catalyst CoPh, CdSe quantum dots (QDs), and TiO₂ nanoparticles (NPs) together via facile self-assembly. The CoPh/CdSe@TiO₂ photocatalyst enables the catalysis of proton and CO₂ reduction reactions and produces syngas under visible light irradiation. The CoPh/CdSe@TiO₂ photocatalyst simultaneously produces CO and H₂ for over 140 hours under visible light irradiation. The efficiencies of CO and H₂ production are 571 μmol g⁻¹ and 1554 μmol g⁻¹, respectively. The CO : H₂ ratio maintains in the range of 1 : 0.6–1 : 2.7, satisfying syngas ratio requirements for F–T synthesis. Mechanism studies revealed that CdSe QD, TiO₂ NP, and CoPh function mainly as a visible light harvester, a H₂ production catalyst, and a CO₂ reduction catalyst, respectively. Photoinduced electron transfers from CdSe QD to CoPh or TiO₂, separately, occur in the ternary photocatalyst. A robust photocatalytic syngas production has been achieved based on the successful assembly of three functional components in one photocatalyst.