Fast Interfacial Carrier Dynamics Modulated by Bidirectional Charge Transport Channels in ZnIn2S4-based Composite Photoanodes Probed by Scanning Photoelectrochemical Microscopy

Limited charge separation/transport efficiency remains the primary obstacle of achieving satisfying photoelectrochemical (PEC) water splitting performance. Therefore, it is essential to develop diverse interfacial engineering strategies to mitigate charge recombination. Despite obvious progress having been made, most works only considered a single-side modulation in either the electrons of conduction band or the holes of valence band in a semiconductor photoanode, leading to a limited PEC performance enhancement. Beyond this conventional thinking, we developed a novel coupling modification strategy to achieve a composite electrode with bidirectional carrier transport for a better charge separation, in which Ti(2)C(3)Tx MXene quantum dots (MQDs) and alpha-Fe2O3 nanodots (FO) are anchored on the surface of ZnIn2S4 (ZIS) nanoplates, resulting in markedly improved PEC water splitting of pure ZIS photoanode. Systematic studies indicated that the bidirectional charge transfer pathways were stimulated due to MQDs as electron extractor and S-O bonds as carriers transport channels, which synergistically favors significantly enhanced charge separation. The enhanced kinetic behavior at the FO/MQDs/ZIS interfaces was systematically and quantitatively evaluated by a series of methods, especially scanning photoelectrochemical microscopy. This work may deepen our understanding of interfacial charge separation, and provide valuable guidance for the rational design and fabrication of high-performance composite electrodes.

Automated summary

Limited charge separation/transport efficiency is still a major challenge in achieving high-performance photoelectrochemical (PEC) water splitting. In this study, a novel coupling modification strategy was developed to achieve bidirectional carrier transport on a composite electrode, resulting in significantly improved PEC water splitting performance of a pure ZnIn2S4 photoanode. The enhanced charge separation was attributed to the stimulated bidirectional charge transfer pathways through MXene quantum dots (MQDs) as electron extractors and S-O bonds as carriers transport channels. This research enhances our understanding of interfacial charge separation and provides valuable guidance for the design and fabrication of high-performance composite electrodes.