Preparation And Properties Of Photoanodes For Photoelectrochemical Oxidation Of Organic Substrates

The splitting of water into O₂and H₂ using photoelectrochemical cells（PECs）is an promising method for solar fuel production.However,from the perspective of practical applications,the efficiency of PEC catalytic water splitting is still low at present owing to the sluggish water oxidation reaction which involvs four-electron and four-proton transfer processes.Apart from the slow kinetics,the O₂ produced by the photoanode has little economic value.Therefore,the water oxidation reaction on the anode can be replaced by a thermodynamically and kinetically more favorable organic substrate oxidation reaction to generate organic chemicals with higher added value than O₂.In pursuit of sustainable and clean production methods,water can be used as an oxygen source for photoelectric organic synthesis,in coupled with cathode hydrogen production.In this paper,a series of porphyrin-manganese molecular catalysts were immobilized on a terpyridine ruthenium functionalized Ti O₂ photoanode to construct dye-sensitized photoanodes（Ti O₂|Ru P,Mn TPP）for organic substrate oxidation.Under visible light irradiation,benzyl alcohol（Bn OH）oxidation was performed with a bias of 0 V（vs.Ag/Ag Cl）to obtain a current density of 1.25 m A/cm².The product was analyzed by high performance liquid chromatography and liquid chromatography-mass spectrometry.The selectivity and Faradaic efficiency of the target product benzaldehyde were 99%,and the turnover number（TON）was 1110.Furthermore,the Mn TPP catalyst was decomposed into a catalytically active Mn O_x transparent films at low substrate concentrations,which was evidenced by electrochemistry,ultraviolet–visible spectroscopy（UV–Vis）,and scanning electron microscopy（SEM）.In addition,we developed an environment benign method for photoelectrocatalytic olefin epoxidation.We report the bromide-mediated photoelectrochemical epoxidation of alkenes at a mesoporous BiVO₄ photoanode and the simultaneous hydrogen evolution at the anode using water as an oxygen source.With this system,the highly efficient epoxidation of water-soluble olefins including sodium p-styrene sulfonate（Na SS）,sodium methallyl sulfonate（Na MAS）,allyl alcohol（AAL）and 3-methyl-3-buten-1-ol（MBL）was achieved with 100%yield and 100%selectivity.The H₂¹⁸O isotope labeling experiment proved that water is the sole source of oxygen for the oxidation reaction.The experimental results show that the Na Br redox mediator not only promotes the oxidation of olefinic"C=C"bonds,but also inhibits the photocorrosion of BiVO₄ electrodes in water.