Size-Dependent Multi-Electron Donation in Metal-Complex Quantum Dots Hybrid Catalyst for Photocatalytic Carbon Dioxide Reduction

The effective conversion of carbon dioxide (CO) into valuable chemical fuels relies significantly on the donation of multiple electrons. Its efficiency is closely linked to both the density and lifetime of excited charge carriers. In this study, a hybrid catalyst system comprising covalently bonded InP/ZnS quantum dots (QDs) and Re-complexes is showcased. The electronic band alignment between the QDs and the Re-complexes is revealed to dominate the multi-electron transfer process for photocatalytic conversion to methane (CH). Notably, the size of the QDs is found to be a determining parameter. Among the three QD sizes investigated, transient absorption spectroscopy studies unveil that rapid multi-electron transfer from the QDs to the Re-catalyst occurs in smaller QDs (2.3 nm) due to the substantial driving force. Consequently, the photocatalytic conversion of CO to CH is significantly enhanced with a turnover number of 6, corresponding to the overall apparent quantum yield of ≈1%. This research underscores the possibilities of engineering multi-electron transfer by manipulating the electronic band alignment within a catalytic system. This can serve as a guide for optimizing photocatalytic CO reduction.