Atomically precise metal nanoclusters (NCs)-based photocatalytic systems have garnered enormous attention owing to the fascinating merits including unique physicochemical properties, quantum confinement effect, and photosensitization effect, which are distinct from conventional metal nanocrystals (NYs). Nevertheless, a systematic comparison between electrons photoexcited from metal NCs and hot electrons from surface plasmonic resonance (SPR) effect of metal NYs in boosting photoelectrochemical water splitting reaction remains blank. Here, we report the strict and comprehensive comparison on the capability of electrons photoexcited from glutathione-capped gold nanoclusters (Au x @GSH) and hot electrons from plasmonic excitation of gold nanoparticles (Au NYs) self-transformed from Au x @GSH to trigger the photoelectrochemical (PEC) water splitting reaction under visible light irradiation. The results indicate that photoelectrons of Au x NCs trigger a more efficient charge transport rate than hot electrons of plasmonic Au NYs in terms of light-harvesting and conversion efficiency under identical conditions. Moreover, charge transfer characteristics in Au x NC- and Au NY-based PEC systems were established. This work would reinforce our deep understanding of these two pivotal sectors of metal nanomaterials for solar energy conversion.

Conjugated polymers are deemed as conductive carrier mediators for engendering the π electrons along the molecular framework, while the role of nonconjugated insulated polymers has been generally overlooked without the capability to participate in the solar-powered oxidation–reduction kinetics and charge-transfer process. Alternatively, considering the ultrashort charge lifetime and significant deficiency of metal nanocluster (NC)-based photosystems, the fine tuning of charge migration over atomically precise ultrasmall metal NCs as novel light-harvesting antennas has so far not yet been unleashed. Here, we unlock the charge-transfer capability of a nonconjugated polymer to modulate the charge flow over metal NCs (Au x and Au25) by such a solid-state nonconductive polymer via a conceptually new chemistry strategy by which l-glutathione (GSH)-capped gold (Au x @GSH) NCs and poly­(diallyl-di­methyl­ammonium chloride) (PDDA) were alternately self-assembled on the metal oxide (MO: WO3, Fe2O3, and TiO2) substrates. The ultrathin nonconjugated PDDA interim layer periodically intercalated in-between Au x (Au25) NC layers concurrently serves as an unexpected charge-transfer mediator to foster the unidirectional electron flow from Au x (Au25) NCs to MOs by forming a tandem charge-transfer chain, hence endowing the multilayered MO/(PDDA-Au x ) n heterostructures with significantly boosted photoelectrochemical water oxidation performance under light irradiation. The unanticipated role of PDDA as a cascade charge mediator is demonstrated to be universal. Our work would unlock the potential charge-transport capability of nonconjugated polymers as a novel charge mediator for solar-to-chemical conversion.

Two unidirectional electron and hole transfer channels were simultaneously constructed in a multilayered heterostructured photoanode via an efficient layer-by-layer assembly for solar-driven water oxidation.

Finely tuning the charge transfer constitutes a central challenge in photocatalysis, yet exquisite control of the directional charge transfer to the target reactive sites is hindered by the rapid charge recombination. Herein, dual separated charge transport channels were fabricated in a one-dimensional transition-metal chalcogenide (TMC)-based system via an elaborate layer-by-layer (LbL) self-assembly approach, for which oppositely charged metal-ion-coordinated branched polyethylenimine (BPEI) and MoS2 quantum dots (QDs) were alternately integrated to fabricate the multilayered TMC@(BPEI/MoS2 QDs) n heterostructures with controllable interfaces. Photocatalytic hydrogen generation performances of such ternary heterostructures under visible light irradiation were evaluated, which unravels that the BPEI layer not only behaves as “molecule glue” to enable the electrostatic LbL assembly with MoS2 QDs in an alternate stacking fashion on the TMC frameworks but also acts as a unidirectional hole-transfer channel. More significantly, transition-metal ions (Fe2+, Co2+, Ni2+, Cu2+, and Zn2+) coordinated on the outmost BPEI layer are able to function as interfacial electron transfer mediators for accelerating the interfacial cascade electron transport efficiency. These simultaneously constructed dual high-speed electron and hole-transfer channels are beneficial for boosting the charge separation and enhancing the photocatalytic hydrogen evolution performances.

Precise tuning of photoinduced charge separation and transport has been an enduringly central issue in photocatalysis but meets with limited success. In particular, controllable, accurate and simultaneous modulation on the...

Crafting spatially controllable charge transfer channels at the nanoscale level remains an enduring challenge in solar-to-chemical conversion technology. Despite the advancements, it still suffers from sluggish interfacial charge transport kinetics and scarcity of strategies to finely modulate charge transport pathways. Herein, this article demonstrates the unexpected charge modulation property of non-conjugated insulating polymer assisted by a universal layer-by-layer self-assembly tactic. Oppositely charged poly(dimethyl diallyl ammonium chloride) (PDDA) and Ti 3 C 2 MXene quantum dots (MQDs) are periodically attached to the wide bandgap metal oxides (WMOs) to design multilayered heterostructured photoanodes. The intermediate PDDA layer acts as an efficacious charge relay medium to access directional electron flow from WMOs to Ti 3 C 2 MQDs, while Ti 3 C 2 MQDs serve as the electron extractor. Charge transfer cascade is thus stimulated on account of the simultaneous electron-trapping capabilities of interim PDDA layer and Ti 3 C 2 MQDs, which synergistically favors the conspicuously boosted charge separation over WMOs, affording the WMOs/(PDDA/MQDs) n photoanodes with considerably enhanced photoelectrochemical (PEC) water oxidation performances. Moreover, PEC performances of such photoanodes can be tuned by interface configuration via assembly number and sequence. This work will provide an insightful perspective to craft a directional charge transfer pathway through insulating polymer for solar energy conversion.

Two spatially separated charge transfer channels were constructed in multilayered photoanodes for efficient solar water oxidation under both simulated and visible light irradiation.

Atomically precise metal nanoclusters (NCs) have recently been unleashed as novel photosensitizers but inevitably suffer from light-induced self-transformation to metal nanocrystals (NYs), leading to substantially reduced photoredox activities. Herein, we conceptually demonstrate how to manipulate the intrinsic instability of metal NCs for smartly crafting long-range cascade charge transfer chain assisted by an ultrathin poly­(dialyldimethylammonium chloride) (PDDA) layer that was intercalated at the interface of metal NCs and semiconductor. The unidirectional electron flow endowed by Schottky-type self-transformed metal NYs and unexpected electron-withdrawing capability of PDDA layer concurrently foster the charge transfer cascade, resulting in the markedly enhanced net efficiency of photocatalytic hydrogen evolution performances under visible light irradiation. Our work opens new frontiers for judiciously harnessing the inherent detrimental instability of metal NCs for boosted charge transfer toward solar-to-hydrogen conversion.