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 BiVO 4 photoanode for efficient photoelectrochemical (PEC) water oxidation. In order to overcome this issue, we introduce Co@β-cyclodextrin (Co@β-CD) supramolecule as oxidation evolution catalyst (OEC) into BiVO 4 photoanode for the first time via a facile two-step immersion method. The optimal Co@β-CD/BiVO 4 photoanode displays a remarkable photocurrent density of 5.3 mA cm −2 at 1.23 V RHE , which is ca. 3.5 times as high as that of pristine BiVO 4 photoanode. Further analyses indicate that photogenerated holes could quickly transfer from BiVO 4 to Co sites through β-CD, thereby suppressing charge recombination. Moreover, due to the spatial confinement effect of β-CD, the dispersed Co sites in Co@β-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.