Solar photocatalytic reduction of carbon dioxide (CO₂) to valuable products such as carbon monoxide, methane, and methanol has become an appealing approach to mitigate the deleterious impact of the combustion of fossil fuels. Quantum dots (QDs), visible light-sensitive nanomaterials, have been widely studied for converting solar energy into chemical energy due to their light-harvesting properties, compositional tunability, and size-dependent energetics. However, bare QDs suffer from photoanodic corrosion and low selectivity toward the reduction of CO₂. To improve their catalytic activity, we have doped CdS QDs with nickel(II) cations and interfaced them with ternary metal-intercalated vanadium oxide (M_xV₂O₅) nanowires (NWs) with intercalative mid-gap electronic states. Within the resulting heterostructures, QDs act as charge donors, and the NWs exhibit functioning as charge acceptors. With the assistance of a solvated Ni(II) co-catalyst, these heterostructures have been proven to produce hydrogen. To expand their potential applications, we are exploring the introduction of Ni(II) into the core of our CdS QDs for CO₂ photoreduction selectivity. This is based on electronic structure considerations to reduce energetic offsets and improve interfacial charge transfer. This presentation will describe the synthesis of photocatalytic heterostructures by interfacing cysteinate-capped nickel(II)-doped CdS QDs (cys-Ni:CdS QDs) with β-Pb_0.33V₂O₅ NWs, the spectroscopic characterization of their excited-state charge-transfer reactivity, and the application of the heterostructures in redox photocatalysis. Transient absorption spectroscopy further evaluates the interfacial charge transfer kinetics of cys-Ni:CdS/β-Pb_0.33V₂O₅ heterostructures to measure excited-state charge-transfer dynamics. The successful doping of QDs slows down the undesirable transfer of photogenerated electrons to NWs, enabling tunability of thermodynamics and kinetics of excited-state electron transfer. Having established that doping the CdS QDs promotes enhanced charge separation, we explored their photocatalytic reactivity. It was discovered that Ni(II) doping boosts the migration of photogenerated charge carriers and narrows the band gap of CdS QDs due to the creation of energy states, resulting in successful CO, CH₄, and H₂ photocatalytic generation.

Jaime Ayala

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