A Suspended Molecular Assembly of Mimicking PSII for Overall Water Splitting Initiated by One-Step Excitation

Photocatalytic water splitting is a promising approach to storing solar energy into chemical bonds. It is significantly challenging to design a photocatalytic system capable of driving overall water splitting into hydrogen and oxygen in only a single junction with one-step excitation under visible-light irradiation. Here, we present an artificial photosystem based on a layer-by-layer assembly to deposit a molecular triad on HCa2Nb3O10 (HCNO) nanosheets. The photocatalyst triad was formed on the oxide nanosheet surface, incorporating a sensitizer, an electron donor, and a water oxidation catalyst, mimicking the essential components of photosystem II to produce oxygen. For hydrogen evolution, the HCNO nanosheets and introduced Pt particles serve as electron acceptors and H2 evolution sites, respectively. This system, supported by transient absorption spectroscopy (TAS) and steady-state photoluminescence (PL) emission spectra, promoted efficient charge separation and ultrafast photogenerated carrier transport to the active sites on the nanosheet with appropriate thermodynamics to perform water splitting. Under visible-light (λ = 420 nm) irradiation, the suspended molecular ‘leaves’ obtained a maximum 0.18% apparent quantum yield (AQY) without degradation during 25 h measurement. This photocatalysis system has good tunability, laying out a promising path for developing photocatalytic overall water splitting under visible-light irradiation on a single junction molecular leaf.