Enhanced bezafibrate degradation and power generation via the simultaneous PMS activation in visible light photocatalytic fuel cell

A collaborative system including peroxymonosulfate (PMS) activation in a photocatalytic fuel cell (PFC) with an BiOI/TiO2 nanotube arrays p-n type heterojunction as photoanode under visible light (PFC(BiOI/TNA)/PMS/vis system) was established. Xenon lamp was used as the light source of visible light. A 4.6 times higher pseudo-first order bezafibrate (BZF) degradation rate constant was achieved in this system compared with the single PFC (BiOI/TNA)/vis system. The radical quenching experiments revealed that the contribution of reactive oxidative species (ROS) followed the order of O-1(2) approximate to h(+) >> center dot OH > SO4 center dot- >>O-2(center dot-). The EPR tests demonstrated that PMS addition enlarged the formation of O-1(2), center dot OH and SO4 center dot-, but suppressed O-2(center dot-) yield. Interestingly, O-1(2) was further proved to dominantly originated from the priority reaction between positive photoinduced holes (h+) and negatively charged PMS. Besides, N2-purging tests and density functional theory calculation indicated that PMS probably reacted with residual photoinduced electron (e-) on the more negative conduction band (CB) of BiOI to form center dot OH and SO4 center dot-, but competed with dissolved oxygen. Other e- transferred to the less negative CB of TNA through p-n junction will efficiently move to cathode through the external circuit. The greatly promoted power generation of PFC system was observed after PMS addition due to extra h+ consumption and efficient e- separation and transfer. Besides, three possible pathways for BZF degradation were proposed including hydroxylation, fibrate chain substituent and amino bond fracture. This study can provide new insights into the mechanisms of PMS assisted photocatalysis and accompanying energy recovery.