Enhancing photocatalytic degradation of organics: synergistic insights from piezo-assisted KNbO3/BiOCl S-scheme heterojunction.

This study elucidates the piezo-photocatalytic degradation of methylene blue (MB) and perfluorooctane sulfonic acid (PFOS) using 50-KNbO₃/BiOCl (50-KNO/BOC) heterojunction. Under artificial lighting (four UV C lamps, 8 W each) and magnetic stirring-induced piezo-assistance (stirring rate ~ 1000 rpm), the Maximum removal reached 90.1% (rate constant, k = 0.0193 min^-1) for MB and 81.1% (k = 0.018 min^-1) for PFOS within 120 min. The degradation mechanism can be illustrated as (1) the increase in the carrier Lifetime to 24.6 ns in 50-KNO/BOC by forming an S-scheme heterojunction, and (2) the induced additional piezo-assistance reduced charge recombination. Furthermore, the scavenging studies have revealed dominance of ^.OH, h⁺, and ^.O₂^- in MB removal. The degradation pathway begins with the demethylation of MB, eventually producing other metabolites and products of degradation. MB removal remained at 83.5% after four cycles of reusing 50-KNO/BOC, evidencing heterojunction's stability. MB was completely removed within 120 min under sunlight-induced piezo-photocatalysis. The energy consumption (EEO) was reduced to 213.43 kWh/m³/order compared with artificial Lighting conditions with EEO of 3715.33 kWh/m³/order.