Boosting photoelectrochemical water oxidation by self-assembled Co@β-cyclodextrin supramolecules modified on BiVO4 photoanode

Severe charge recombination and poor surface water oxidation kinetics are key restrictions of BiVO4 photoanode for efficient photoelectrochemical (PEC) water oxidation. In order to overcome this issue, we introduce Co@beta- cyclodextrin (Co@beta-CD) supramolecule as oxidation evolution catalyst (OEC) into BiVO4 photoanode for the first time via a facile two-step immersion method. The optimal Co@beta-CD/BiVO4 photoanode displays a remarkable photocurrent density of 5.3 mA cm -2 at 1.23 VRHE, which is ca. 3.5 times as high as that of pristine BiVO4 photoanode. Further analyses indicate that photogenerated holes could quickly transfer from BiVO4 to Co sites through beta-CD, thereby suppressing charge recombination. Moreover, due to the spatial confinement effect of beta-CD, the dispersed Co sites in Co@beta-CD are considered to possess the high catalytic activity in similar with single -atom catalyst, which accelerates the surface water oxidation kinetics. This work not only demonstrates the superiority of supramolecule/semiconductor composite photoanode, but also provides a facile preparation route for the large-scale preparation of high -performance photoanodes.