Crystal-Facet-Dependent Piezocatalytic Activity of BiFeO3 Nanosheets for H2 Evolution and Environmental Remediation

Reasonable adjustment of the exposed crystal facets has been proven to be an effective strategy to improve the activity of the catalyst. However, the crystal-facet-dependent piezoactivity is rarely investigated. In this work, BiFeO3 with highly exposed (012) or (110) crystal facets were synthesized by adjusting the volume ratio of solvent and reaction time. Ethylene glycol was used as a structure-directing agent for the synthesis of BiFeO3 nanosheets (BiFeO3–NS) with highly exposed (012) facets. BiFeO3–NS shows an obvious higher piezoelectric catalytic hydrogen evolution rate than that of BiFeO3 nanoparticles (BiFeO3–NP) with highly exposed (110) facets. In addition, the rate constant of BiFeO3–NS for the piezocatalytic degradation of rhodamine B (RhB) shows a 2-fold increase than that of BiFeO3–NP. A variety of controlled experiments have been performed. It is revealed that these two nanomaterials exhibit comparable specific surface areas and adsorption capacity. BiFeO3–NS possesses narrowed bandgap as compared to that of BiFeO3–NP. The enhanced piezocatalytic activity of BiFeO3–NS can be attributed to its built-in electric field, strong carrier mobility, and effective charge separation efficiency. This study provides an alternative perspective for piezoelectric catalysis in surface engineering.