Unleashing Insulating Polymer as Charge Transport Cascade Mediator

Abstract 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 Ti₃C₂ 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 Ti₃C₂ MQDs, while Ti₃C₂ 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 Ti₃C₂ 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.