Atomically Precise Metal Nanocluster Photosystem: Electron Relay Boosts Photocatalytic Organic Transformation

Abstract

Atomically precise metal nanoclusters (NCs) demonstrate emerging potential as a new generation of photosensitizers in photoredox catalysis. However, metal NCs suffer from intrinsic poor instability, which leads to the loss of photosensitization effect and hampers their widespread applications in heterogeneous photocatalysis. Herein, we corroborate the design of a spatially directional charge transfer pathway over transition metal chalcogenide (TMC)based heterostructures by way of a facile and efficient electrostatic self-assembly approach. Positively charged solid-state nonconjugated insulating polymer of poly(allylamine hydrochloride) (PAH) and negatively charged glutathione (GSH) capped metal NCs [Ag 9 @(GSH) 6 ] as building blocks were controllably and highly ordered anchored on the TMC substrate. It was unveiled that owing to the appropriate energy level alignment and interface configuration, photogenerated electrons over metal NCs can directionally flow to the TMC substrate with the aid of PAH, which functions as an interfacial charge transfer mediator, and simultaneously holes migrate in the opposite direction, thereby collaboratively contributing to substantially boosted charge separation and prolonged charge lifetime. Benefiting from these merits, the thus self-assembled TMCs/PAH/metal NC heterostructure unfolds conspicuously enhanced photoactivity toward anaerobic selective photocatalytic reduction of nitroaromatics to amino derivatives under visible light irradiation. This work would significantly reinforce our fundamental understanding of the charge transfer characteristic of atomically precise metal NCs and the charge-withdrawing capability of solid insulating polymers for solar energy conversion.

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

“…On account of the appropriate energy-level alignment between BiVO 4 and Ag x @GSH NCs, photoelectrons in the LUMO of Ag x @GSH NCs can idiopathically migrate to the CB of BiVO 4 and then transfer to the cathode along the external circuit to participate in water reduction to hydrogen, while holes in the HOMO level of Ag x @GSH NCs actuate the water oxidation to oxygen. In view of the fact that charge transfer resistance of BP photoanode (Figure a–c) is hardly changed relative to BiVO 4 , we speculate that PAH layer indeed functions as an insulating layer and does not participate in the interfacial charge-transfer process. − Simultaneously, the holes generated by BiVO 4 photoexcitation collaborate with the holes on Agx@GSH NCs to facilitate water oxidation. In this way, electrons photoexcited over Ag x @GSH NCs are capable of smoothly transferring from Ag x @GSH NCs to BiVO 4 substrate by tunneling the ultrathin insulating PAH interim layer, fulfilling the charge separation process and boosting the PEC water oxidation performances in an insulating polymer-mediated and atomically precise metal nanoclusters-photosensitized photosystem.…”

Recent progress in atomically precise metal nanoclusters for photocatalytic application

“…6(c)). 67 In the CdSe–Au x NCs–graphene system, Au x NCs and CdSe both acted as the photosensitizer. More importantly, Au NCs were used as an intermediate charge relay mediator, and graphene provided the electron-withdrawing capability, synergistically promoting interfacial charge transfer and separation, leading to enhanced photoactivity towards the selective reduction of aromatic nitro compounds to amino derivatives (Fig.…”