Ultrathin BiOCl-OV/CoAl-LDH S-scheme heterojunction for efficient photocatalytic peroxymonosulfate activation to boost Co (IV)=O generation

•2D/2D ultrathin S-scheme BiOCl-OV/CoAl-LDH heterojunction were constructed.•OV reduced electron occupation of the Co 3d-orbital.•S-scheme heterojunction accelerates the photogenerated electrons transfer.•The designed system shows high removal capability for the actual wastewater. Sustainable and rapid production of high-valent cobalt-oxo (Co(IV)=O) species for efficiently removing organic pollutants is challenging in permoxymonosulfate (PMS) based advanced-oxidation-processes (AOPs) due to the limitation of the high 3d-orbital electronic occupancy of Co and slow conversion from Co(III) to Co(II). Herein, S-scheme BiOCl-OV/CoAl-LDH heterojunction were constructed by ultrathin BiOCl with the oxygen-vacancy (OV) self-assembled with ultrathin CoAl-LDH. OV promoted the formation of charge transfer channel (Bi-O-Co bonds) at the interface of the heterojunction and reduced electron occupation of the Co 3d-orbital to facilitate the generation of Co(IV)=O in the BiOCl-OV/CoAl-LDH/PMS/Visible-light system. S-scheme heterojunction accelerated the photogenerated electrons to allow rapid conversion of Co(III) to Co(II), promoting the fast two-electron transfer from Co(II) to Co(IV)=O. Consequently, the developed BiOCl-OV/CoAl-LDH/PMS/Visible-light system showed excellent degradation efficiency for most of organic pollutions, and exhibited very high removal capability for the actual industrial wastewater. This study provides a new insight into the evolution of Co(IV)=O and the coordinative mechanism for photocatalysis and PMS activation. This study finding that the introduction of oxygen-vacancy (OV) significantly promotes the formation of chemical bonds (Bi-O-Co) at the heterointerface of 2D/2D ultrathin S-scheme BiOCl-OV/CoAl-LDH heterojunctions, leading to the electronic delocalization around Co sites and reducing the occupancy of the Co 3d-orbital. Additionally, the ultrathin S-scheme heterojunction facilitates the migration of photogenerated electrons from BiOCl-OV to Co sites in the CoAl-LDH, accelerating conversion of Co(III) to Co(II) and realizing a smooth cycle of Co(II)-Co(IV)-Co(II). [Display omitted]