Selective Activation of Benzyl Alcohol Coupled with Photoelectrochemical Water Oxidation via a Radical Relay Strategy

Selective oxidation to produce target chemicals usually need activation of O-2 at high temperature and/or pressure, which have largely restricted its practical operation and application. Here, we put forward a radical relay strategy coupling photoelectrochemical (PEC) water oxidation toward efficiently selective conversion of benzyl alcohol (BA) to benzaldehyde (BAD). An illuminated BiVO4 (BVO) photoanode covered with an ultrathin (similar to 3 nm) hydrothermally synthesized layered double hydroxide (U-LDH) catalyst and graphene (G) exhibited >99% selectivity to BAD (1.2 V vs. RHE). Mechanistic studies and DFT calculation verified that the hydroxyl radicals (center dot OH) generated from the oxidation of water are bound to the surface of U-LDH through hydrogen-bonding interactions and the energy is lowered. Fourier transform infrared spectroscopy showed that BA is adsorbed to the U-LDH catalyst, but BAD is not. Thus, the selectivity is favored not only by the controlled oxidation capacity of center dot OH radicals but the desorption of the desired product from the catalyst before further oxidation occurs. This work introduces an alternative PEC way to achieve mild and selective oxidation of BA derivatives based on ternary G@U-LDH@BVO catalysts.