Excellent stability of molecular catalyst/BiVO4 photoanode in borate buffer solution

Abstract

Solar-driven photoelectrochemical water splitting is a promising solution to energy problem. However, not-yet-available long-term stability of photoelectrodes inhibits their practical application. Introducing structure tunable, highly active and easily prepared molecular catalysts is an efficient approach to improve their stability and has recently attracted great attention. Nonetheless, the long-term stability is still challenged due to regeneration of molecular catalyst during stability test. Herein, tannic acid coordinated with Ni and Fe ions (TANF) molecular catalyst is immobilized on BiVO4 photoanode for oxygen evolution reaction (OER). Taking advantage of the regeneration of molecular catalyst, effects of buffer species on activity, stability and regeneration of TANF/BiVO4 photoanodes are investigated. In an optimal borate electrolyte, the TANF/BiVO4 photoanode shows nearly no-decay after operating at harsh conditions (at 1.2 VRHE with continuous light illumination) for 62 h. The long-term stability profits from the regenerated catalyst, which is composed of a carbon conductive network with metal oxides/hydroxides as OER-active sites. This excellent stability of the integrated photoanode surpasses most of existing OEC/BiVO4 photoanodes, and the stabilized catalyst is comparable with the state-of-the-art FeOOH/NiOOH dual-cocatalyst and ferrihydrite catalyst.