Polar Layered Bismuth-Rich Oxyhalide Piezoelectrics Bi_4O_5X_2 (X=Br, I): Efficient Piezocatalytic Pure Water Splitting and Interlayer Anion-Dependent Activity

摘要

Piezocatalytic pure water splitting for H2 evolution carries the virtuesof efficacious utilization of mechanical energy, easy operation, andhigh value-added products, while lacking desirable piezoelectrics forhigh chemical energy production. Here, two polar layered bismuth-richoxyhalides Bi_4O_5X_2 (X=Br, I) thin nanosheets (≈4 nm) are first exploitedas efficient piezocatalysts to be capable of dissociating pure water. Theunique asymmetrical layered structures of Bi_4O_5X_2 (X=Br, I) composed ofthe interleaved Bi_4O_5~（2+） layer and double X? ions slabs along the 1 0 1_orientation cause large intrinsic dipole moment, excellent piezoelectricityand easy deformation. Without any cocatalyst and sacrificial agent, Bi_4O_5Br_2and Bi_4O_5I_2 thin nanosheets display remarkable piezocatalytic H_2 productionrate of 1149.0 and 764.5 μmol g~(?1) h~(?1), respectively, standing among thebest piezocatalysts, accompanied by H_2O_2 and hydroxyl radicals (·OH)as oxidative products. The smaller radius and higher electronegativityof interleaved Br than I cause a more strongly polar crystal structure inBi_4O_5Br_2, contributing to the higher piezocatalytic activity compared toBi_4O_5I_2. This study broadens the scope of piezoelectric materials appliedto sustainable energy catalysis by efficiently converting mechanical energyand illustrates the importance of crystal configuration and composition infabricating efficient piezocatalytic systems.