Subsurface Defect Engineering in Single-Unit-Cell Bi2WO6 Monolayers Boosts Solar-Driven Photocatalytic Performance

Defect engineering in photocatalysts represents a fundamental method toward tailoring their solar-to-chemical energy conversion performance, although determining the nature and impact of subsurface defects remains challenging. Single-unit-cell Bi2WO6 monolayers, forming a sandwich-like structure, [BiO](+)-[WO4](2-)-[BiO](+), exhibit promising photocatalytic performance and are an ideal system for isolating subsurface defects. We report the single-step synthesis of Bi2WO6 monolayers rich in stable interior W vacancies and characterize their influence on the physical properties necessary for effective photocatalytic surface reactions. Defect-rich monolayers benefit from enhanced visible-light absorption and photocarrier transport, boosting the solar photocatalytic oxidation of benzylic alcohols by 140% at no cost to selectivity or stability. This work highlights the importance of subsurface defects within surface-driven photocatalytic applications and prescribes a general strategy for their isolated study via 2D compounds exhibiting symmetric surface termination.