Charge modulation over atomically precise metal nanoclusters via non-conjugated polymers for photoelectrochemical water oxidation

Abstract

Atomically precise metal nanoclusters (NCs) have emerged as a pivotal sector of metal nanomaterials due to their unique atomic stacking mode, quantum confinement effect and abundant active sites. In particular, the discrete energy band structure of metal NCs renders them emerging photosensitizers. Nonetheless, atomically precise metal NCs suffer from ultrashort charge lifetime and poor stability, impeding the construction of robust and stable metal NC-based photosystems. Herein, we designed multilayered metal oxide (MO)/(metal NCs/insulating polymer)_n (metal NCs: Au_x@GSH, Ag_x@GSH, and Au₂₅@GSH₁₈ NCs) heterostructured photoanodes, wherein glutathione (GSH)-capped metal NCs and an ultra-thin non-conjugated insulating poly(allylamine hydrochloride) (PAH) layer are electrostatically layer-by-layer self-assembled on MO substrates in a periodic face-to-face stacking mode. We infer that electrons photoexcited over metal NCs in MOs/(metal NCs/PAH)_n photosystems can be effectively extracted and tunneled to the adjoining MO substrates through the insulating polymer interim layer by engendering the tandem charge transfer pathway, thus significantly boosting the visible-light-driven photoelectrochemical water oxidation. This work opens up a new frontier for strategically mediating tunable charge transport over atomically precise metal NCs towards solar-to-hydrogen conversion.