Hole Polaron-Mediated Suppression of Electron-Hole Recombination Triggers Efficient Photocatalytic Nitrogen Fixation

In the pursuit of successful photocatalytic transformations, challenges persist due to limitations in charge carrier utilization and transfer efficiency, which stemming from rapid recombination. Overcoming these limitations necessitates the exploration of novel mechanisms that enhance the effective separation of photogenerated electron-hole pairs. Herein, deviating from the conventional approach of enhancing carrier migration to separate photogenerated charges and extend their lifetime, the proposal is to directly prevent the recombination of photogenerated electrons and holes by forming hole polarons. Specifically, disordered pores are introduced on the surface of KTaO₃ ultrathin sheets, and the clear-cut evidences in electron paramagnetic resonance, photoluminescence, and ultrafast spectroscopy unambiguously confirm the enhanced carrier-phonon coupling, which results in the formation of hole polarons to impede the recombination of photogenerated electron-hole pairs. Taking the challenging nitrogen oxidation reaction as an example, it is found that the hole polarons in atomic-disordered pore KTaO₃ ultrathin nanosheets trigger outstanding photo-oxidation performance of  nitrogen (N₂)to nitrate, with a nitrate-producing rate of 2.1 mg g^-1 h^-1. This scenario is undoubtedly applicable to a wide variety of photocatalytic reactions due to the common challenge of charge carrier recombination in all photocatalytic processes, manifesting broad implications for promoting photocatalysis performance.