Halogen-Tuned BiOI-Cl Solid Solutions with Enhanced Built-In Electric Field for Superior Piezo-Photocatalytic Performance

The piezo-photocatalytic performance of BiOI_(1-<i>x</i>)Cl_<i>x</i> solid solutions was systematically investigated to unravel the role of built-in electric field regulation in charge carrier dynamics and to explore the potential of multifield coupled catalysis for environmental remediation. Comprehensive characterization confirmed halogen substitution modulates piezoelectricity, optical absorption, and charge separation efficiency. Using rhodamine B (RhB) as a model pollutant, the BiOI_0.25Cl_0.75 solid solution achieved 99.9% degradation within 16 min, with a rate constant 1.53 times higher than piezocatalysis and 3.18 times that of photocatalysis alone, distinctly outperforming pristine BiOI and BiOCl. This superior activity arises from the synergistic effects of halogen-induced band structure tuning and the amplified piezoelectric field under mechanical stress, accelerating charge transfer and suppressing recombination. These findings highlight BiOI_0.25Cl_0.75 solid solutions as efficient multifunctional catalysts and demonstrate piezo-photocatalysis as a sustainable pathway for harnessing solar and mechanical energy toward environmental purification.