ABSTRACT
Atomically precise alloy nanoclusters (NCs) inherit the advantages of homometal NC counterparts such as atomic stacking fashion, quantum confinement effect, and enriched catalytic active sites and simultaneously possess the advantageous physicochemical properties such as significantly enhanced photostability, ideal photosensitization efficiency, and favorable energy band structure. Nevertheless, elucidation of the roles of alloy NCs and alloy nanocrystals (NYs) in boosting solar water oxidation has so far not yet been reported owing to the deficiency of applicable alloy NC photosystems. Herein, utilizing the generic thermal-induced self-transformation of alloy NCs to alloy NYs, we comprehensively explore the photosensitization properties of glutathione (GSH)-capped alloy NCs (AgxAu1-x@GSH and CuxAu1-x@GSH) and the corresponding alloy NY (AgAu and CuAu) counterparts in solar water oxidation reaction. The results imply that photoelectrons of alloy NCs surpass the hot electrons over plasmonic alloy NYs in stimulating the PEC water oxidation reaction. The photoelectrons of alloy NCs demonstrate lower interfacial charge-transfer resistance, longer carrier lifetime, and a more enhanced photosensitization effect with respect to the plasmonic alloy NYs, contributing to the significantly boosted photoelectrochemical water oxidation activities. Moreover, we found that our result is universal.
ABSTRACT
Transition-metal chalcogenide quantum dots (TMC QDs) show great promise in artificial photosynthesis for excellent light-harvesting capability. Nonetheless, TMC QDs have limitations of ultrafast charge recombination rate, sluggish carrier migration kinetics, and generic photocorrosion, retarding their widespread applications. To solve these obstacles, herein, we demonstrate the stimulation of charge migration over TMC QDs with the aid of nonconjugated insulating polymer and graphene (GR) for a versatile photoredox selective organic transformation. To this end, an ultrathin insulating polymer layer, i.e., poly(allylamine hydrochloride) (PAH), grafted on the GR framework, is electrostatically intercalated at the interface of TMCs QDs and the GR framework via a self-assembly for constructing TMC QDs/PAH/GR three-dimensional spatially multilayered heterostructures. In this well-defined nanoarchitecture, TMC QDs function as a light-harvesting antenna, GR as a terminal electron reservoir, and PAH as an intermediate interfacial charge relay mediator. We ascertain that the ultrathin PAH interim layer unexpectedly fosters the photoelectron migration from TMCs QDs to the GR framework in a tunable fashion, boosting the charge separation of TMCs QDs and resulting in significantly improved photoactivities toward anaerobic reduction of aromatic nitro compounds to amino derivatives and oxidation of alcohols to aldehydes under visible light. Photoredox catalysis mechanisms of such TMC QDs/PAH/GR photosystems are elucidated, and the active species in these photoredox organic conversion reactions are comprehensively determined. Our work would open new frontiers to finely modulate the charge transport of TMCs QDs via nonconjugated insulating polymers for solar energy conversion.
