Photoelectrocatalytic C-H halogenation over an oxygen vacancy-rich TiO2 photoanode

Photoelectrochemical cells are promising tools for C-H functionalisation coupled with H2 production. In this work, Duan et. al., reported the photoelectrocatalytic C-H halogenation to produce organic halides of industrial and medicinal importance with promoted H-2 production. Photoelectrochemical cells are emerging as powerful tools for organic synthesis. However, they have rarely been explored for C-H halogenation to produce organic halides of industrial and medicinal importance. Here we report a photoelectrocatalytic strategy for C-H halogenation using an oxygen-vacancy-rich TiO2 photoanode with NaX (X=Cl-, Br-, I-). Under illumination, the photogenerated holes in TiO2 oxidize the halide ions to corresponding radicals or X-2, which then react with the substrates to yield organic halides. The PEC C-H halogenation strategy exhibits broad substrate scope, including arenes, heteroarenes, nonpolar cycloalkanes, and aliphatic hydrocarbons. Experimental and theoretical data reveal that the oxygen vacancy on TiO2 facilitates the photo-induced carriers separation efficiency and more importantly, promotes halide ions adsorption with intermediary strength and hence increases the activity. Moreover, we designed a self-powered PEC system and directly utilised seawater as both the electrolyte and chloride ions source, attaining chlorocyclohexane productivity of 412 mu mol h(-1) coupled with H-2 productivity of 9.2 mL h(-1), thus achieving a promising way to use solar for upcycling halogen in ocean resource into valuable organic halides.

Automated summary

Photoelectrochemical cells have been proposed as promising tools for C-H functionalisation and H2 production. In this work, a photoelectrocatalytic strategy using an oxygen-vacancy-rich TiO2 photoanode was developed for efficient production of organic halides. This approach demonstrated broad substrate scope and high productivity using seawater as the electrolyte and chloride ions source.