Steering bi-directional charge transfer via non-conjugated insulating polymer

Abstract

Exquisite tuning of spatial charge transfer and separation has been an enduringly core issue in heterogeneous photocatalysis. Nevertheless, precise modulation of directional charge transfer to the ideal catalytically active sites remains challenging owing to rapid recombination rate of photoinduced charge carriers and sluggish charge transfer kinetics. Herein, bi-directional spatially separated electron and hole transport channels were simultaneously constructed over transition metal chalcogenides (TMCs)-based heterostructures via an efficient and facile electrostatic self-assembly strategy. Tailor-made positively charged non-conjugated polymer of branched polyethyleneimine (BPEI) and negatively charged metal nanocrystals (NCs) building blocks were controllably anchored on the TMCs substrate. We found that electrons photoexcited over TMCs substrate can migrate spontaneously, smoothly and unidirectionally to the tightly integrated neighboring metal NCs, wherein metal NCs function as Schottky-type electron-trapping reservoirs and the ultra-thin intermediate BPEI layer serves as a directional hole transport mediator, thus synergistically contributing to the significantly enhanced charge separation and prolonged charge lifetime. Benefiting from these merits, such self-assembled TMC@BPEI/metal heterostructure exhibits the markedly enhanced photoreduction catalysis toward photocatalytic hydrogen generation and anaerobic selective reduction of nitroaromatics to amino derivatives under visible light irradiation. Our work would provide inspiring idea for fine modulation of charge separation and transfer toward solar-to-chemical energy conversion.