Enhancement of Solar‐Driven Photocatalytic Activity of BiOI Nanosheets through Predominant Exposed High Energy Facets and Vacancy Engineering

The increasing application of exposed high energy facet is an effective strategy to improve the photocatalytic performance of photocatalysts because the vacancies are beneficial to photocatalytic reaction. Vacancy dominates numerous distinct properties of semiconductor materials and thus plays a conclusive role in the photocatalysis applications. In this work, two kinds of BiOI nanomaterials with different vacancies are synthesized via a facile solvothermal method. The positron annihilation analysis shows that the thinner BiOI nanosheets possess larger‐sized vacancy than BiOI nanoplates. Thus, BiOI nanosheets show the enhanced separation efficiency of electron–hole pairs and adsorption ability for contaminants under visible light. The results are also validated with the first‐principle computation. Therefore, higher photocatalytic activity to the photodegradation of tetracycline is observed from the nanosheets than that obtained from BiOI nanoplates. This work not only arouses attention to vacancies, but also opens up an avenue for precision design of vacancies to prepare novel photocatalytic materials driven under solar light. The exposed high energy facet is identified as an effective measure to improve the photocatalytic performance of photocatalysts. The existence of vacancy defects is also beneficial to extend region of light absorption, photogenerated carrier transfer, and modulate electrical band structure. BiOI nanosheets exhibit excellent photocatalytic performance due to the combination of high energy facet and large‐sized vacancy defect.