Photoelectrochemical Oxidation of Amines to Imines and Production of Hydrogen through Mo-Doped BiVO4 Photoanode

Imines are important multifunctional intermediates for the synthesis of pesticides, pharmaceuticals, biologics, and fine chemicals. The direct photoelectrochemical (PEC) oxidation of amines to imines is a highly selective, efficient, green, and gentle method. Interestingly, the constructive merging of the PEC oxidation of amines with the production of hydrogen can accelerate hydrogen evolution due to the less challenging oxidation of amines such as benzylamine (BN) in comparison to sluggish water oxidation. Herein, Mo-doped BiVO4 photoanodes were prepared and first applied to simultaneously oxide benzylamine (BN) to N-benzylidenebenzylamine (BI) and produce hydrogen in a closed two-chamber, three-electrode PEC cell After illumination at a bias of 1.3 V vs SCE for 3 h, the 3% Mo-doped BiVO4 photoanode achieved a maximum yield of similar to 94 mu mol h(-1) at a 1 x 1 cm(2) area with a BN to BI selectivity of almost 100% and a Faradaic efficiency of 98.4%. Our electrode presented enhanced photocorrosion resistance in acetonitrile solvent. Additionally, the PEC oxidations of benzylamine derivatives with different substituents (-F, -Cl, -Br, -CH3, -OCH3) to the corresponding imines were also investigated. The results indicated that the Mo-doped BiVO4 photoanode exhibited an excellent performance in the oxidation of these benzylamine derivatives with corresponding amine to imine selectivities of almost 100% and Faradaic efficiencies of >95%.

Automated summary

This study presents a method for direct photoelectrochemical oxidation of amines to imines using Mo-doped BiVO4 photoanodes. The method demonstrates high selectivity, efficiency, environmental friendliness, and mild reaction conditions. Under illumination, the photoanode achieves efficient oxidation of benzylamine with almost 100% selectivity. Additionally, the photoanode exhibits excellent performance in the oxidation of various benzylamine derivatives.