Crafting Insulating Polymer Mediated and Atomically Precise Metal Nanoclusters Photosensitized Photosystems Towards Solar Water Oxidization

Atomically precise metal nanoclusters (NCs) have been deemed as a new generation of metal nanomaterials because of their characteristic atomic stacking fashion, quantum confinement effect, and multitude of active sites. The discrete molecular-like energy band structure of metal NCs endows them with photosensitization capability for light harvesting and conversion. However, applications of metal NCs in photoelectrocatalysis are limited by the ultrafast charge recombination and unfavorable stability, impeding the construction of metal NC-based photosystems. In this work, we elaborately crafted multilayered metal oxide (MO)/(metal NCs/insulating polymer)(n) photoanodes by a facile layer-by-layer (LbL) assembly technique. In these well-defined heterostructured photoanodes, glutathione (GSH)-wrapped metal NCs (Ag-x@GSH, Ag-9@GSH(6), Ag-16@GSH(9), and Ag-31@GSH(19)) and an insulating poly(allylamine hydrochloride) (PAH) layer are alternately deposited on the MO substrate in a highly ordered integration mode. We found that photoelectrons of metal NCs can be tunneled into the MO substrate via the intermediate ultrathin insulating polymer layer by stimulating the tandem charge transfer route, thus facilitating charge separation and boosting photoelectrochemical water oxidation performances. Our work would open a new frontier for judiciously regulating directional charge transport over atomically precise metal NCs for solar-to-hydrogen conversion.