Precise Tuning of Coordination Positions for Transition-Metal Ions via Layer-by-Layer Assembly To Enhance Solar Hydrogen Production

Abstract

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.

Unexpected Boosted Solar Water Oxidation by Nonconjugated Polymer-Mediated Tandem Charge Transfer

“…To evaluate the interfacial charge-transport dynamics of photoelectrodes, electrochemical impedance spectroscopy (EIS) results under light irradiation (AM 1.5 G) were probed. The semicircular arc radius of the EIS curve is closely associated with the charge-transport behavior at the electrode/electrolyte interface, and normally the smaller semicircular arc radius causes the lower charge-transfer resistance. , As exhibited in Figure f, WO 3 -(PDDA-Au x ) 2 has the smallest semicircle arc radius compared to those of other photoelectrodes, indicating that alternate assembly of the PDDA layer and Au x @GSH NCs on the WO 3 NPAs facilitates the interfacial charge-transfer efficiency. The fitted EIS results of photoanodes are summarized in Table S3, which reveals the analogous variation trends in LSV, I – t , and OCVD results.…”

Unleashing non-conjugated polymers as charge relay mediators

“…Detailed characterization of the ZIS/ BPEI/MQD, ZIS/PAH/MQD, ZIS/AET/MQD and ZIS/APTES/MQD heterostructures is provided in Fig. S (25)(26)(27)(28), † which conrms the deposition of MQDs on the ZIS substrate from the perspectives of crystalline structure, optical properties, microscopic morphology and elemental composition. Photocatalytic performances of these heterostructures toward 4-NA reduction and hydrogen evolution are probed to evaluate the general role of such continuous charge transfer channels constructed over ZIS/MQD-based photosystems.…”

“…Polyelectrolytes (PEs), which are dened as polymers with positively or negatively charged properties in repeating monomeric units, 22,23 have been extensively utilized as surface charge modiers to fabricate spatially multilayered multi-dimensional nano-architectures in a precise, controllable and exquisite manner at the nanoscale level. [24][25][26][27] In these ways, PEs mainly play a crucial role as self-assembly initiators, by which oppositely charged building blocks are well organized into well-dened heterostructures. However, utilizing PEs that are mainly composed of non-conjugated polymers as the carrier mediator to regulate the vectorial charge transport pathways has so far not yet been reported in terms of their intrinsic insulating properties in the solid state.…”

Self-assembled transition metal chalcogenides@CoAl-LDH 2D/2D heterostructures with enhanced photoactivity for hydrogen evolution

“…), which possess desirable characteristics, such as adjustable direct band gap and wide optical absorption range, representing a family of visible light-responsive photocatalysts with promising performances for H 2 evolution. 8–12 On the other hand, their photocatalytic activity is limited by the high bulk recombination of photogenerated charge carriers and the deficiency of active sites. In this regard, the state-of-the-art approach to boost the photocatalytic performance is constructing TMC-based hybrid photocatalyst systems.…”