A Cobalt@Cucurbit[5]uril Complex as a Highly Efficient Supramolecular Catalyst for Electrochemical and Photoelectrochemical Water Splitting

A host-guest complex self-assembled through Co2+ and cucurbit[5]uril (Co@CB[5]) is used as a supramolecular catalyst on the surface of metal oxides including porous indium tin oxide (ITO) and porous BiVO4 for efficient electrochemical and photoelectrochemical water oxidation. When immobilized on ITO, Co@CB[5] exhibited a turnover frequency (TOF) of 9.9 s(-1) at overpotential eta=550 mV in a pH 9.2 borate buffer. Meanwhile, when Co@CB[5] complex was immobilized onto the surface of BiVO4 semiconductor, the assembled Co@CB[5]/BiVO4 photoanode exhibited a low onset potential of 0.15 V (vs. RHE) and a high photocurrent of 4.8 mA cm(-2) at 1.23 V (vs. RHE) under 100 mW cm(-2) (AM 1.5) light illumination. Kinetic studies confirmed that Co@CB[5] acts as a supramolecular water oxidation catalyst, and can effectively accelerate interfacial charge transfer between BiVO4 and electrolyte. Surface charge recombination of BiVO4 can be also significantly suppressed by Co@CB[5].

Automated summary

A host-guest complex assembled from Co2+ and cucurbit[5]uril (Co@CB[5]) is utilized as a supramolecular catalyst for efficient electrochemical and photoelectrochemical water oxidation on metal oxide surfaces such as porous indium tin oxide (ITO) and porous BiVO4. The complex exhibits high catalytic activity and accelerates charge transfer between BiVO4 and electrolyte, while suppressing surface charge recombination.