Piezo-Photocatalytic and Photocatalytic Bismuth Vanadate Nanorods with Antibacterial Property

Piezo-photocatalysis, which combines the piezoelectric and photoresponsive behavior of materials, is considered a promising strategy for water treatment. As an established piezomaterial, herein, we report the photocatalytic, piezocatalytic, and piezo-photocatalytic responses of bismuth vanadate (BiVO4) nanorods under ultrasonic frequency (35 kHz) and selected visible light excitation. We used a facile hydrothermal method to produce BiVO4 nanorods. The as-synthesized (B180) and calcined (C300, C500, and C700) BiVO4 crystallizes in the monoclinic scheelite phase. The essential traits shown by BiVO4 nanorods are extended visible-near-infrared absorption and high Bi5+/Bi3+ and V4+/V5+ ratios, inferring a high content of oxygen defects. The photo and piezo responsive behavior are tested with Methylene Blue (MB) as a standard organic pollutant. The piezocatalytic and piezo-photocatalytic processes are activated in BiVO4 through feeding ultrasonic mechanical vibrations, which elicit polarization and separation of charges in BiVO4 nanorods. The photocatalytic and piezo-photocatalytic methods led to 97.63 and 97.13% MB degradation in 40 min. It is found that piezo-photocatalysis is dominant for a short period, but eventually, it slows with time. It can be ascribed to sonication's fracturing effect, which further exacerbates the catalytic process due to the damage to the catalytic sites. Additionally, the photocatalytic inactivation of Gram-positive Staphylococcus aureus) and Gram-negative Escherichia coli K12) bacteria was investigated under visible light irradiation using C300 and C500 samples. Within 120 min, C500 exhibited 97.24 and 90.44% mortality rates compared to C300, exhibiting 72.83 and 71.16% against S. aureus and E. coli K12, respectively.