Engineering Interfacial Energetics: A Novel Hybrid System of Metal Oxide Quantum Dots and Cobalt Complex for Photocatalytic Water Oxidation

Here we reported a novel hybrid photocatalytic water oxidation system, containing metal oxide (n-Fe₂O₃ or p-Co₃O₄) quantum dots (QDs) as light harvester, a salophen cobalt(II) complex (CoSlp) as redox catalyst and persulfate (S₂O₈²⁻) as sacrificial electron acceptor, for oxygen generation from fully aqueous solution. The n-Fe₂O₃ QDs/CoSlp and p-Co₃O₄ QDs/CoSlp systems exhibited good O₂ evolution performances, giving turnover numbers (TONs) of ca. 33 and ca. 35 over CoSlp after visible light irradiation for 72 h, respectively. The excellent photocatalytic performance could be ascribed to the efficient hole transfer from QDs to CoSlp catalyst, leading to reduced photogenerated charge recombination, as well as the CoSlp engineered interfacial band bending of QDs, increasing the driving force or decreasing the energy barrier for hole transfer and then benefiting the following O₂ generation at the QDs/electrolyte interface. The present work successfully demonstrated a novel hybrid system for photocatalytic O₂ evolution from fully aqueous solution; and the essential role of cobalt complexes in engineering the interfacial energetics of semiconductors (n- or p-type) and electrolytes could be informative for designing efficient systems for solar water splitting.