(Invited) A New Strategy to Enhance Long-Term Photostability of BiVO4 Photoanodes for Solar Water Splitting

Abstract

As the performance of photoelectrodes used in in a photoelectrochemical cell (PEC) for water splitting continues to improve, concurrently improving their photostabilities has become an important issue. In this presentation, we report a new strategy to suppress photocorrosion of photoelectrodes using a BiVO4 photoanode as an example. BiVO4 has been recently identified as a promising oxide-based photoanodes for solar water splitting owing to many of its uniquely advantageous features. Anodic photocorrosion of BiVO4 photoanodes involves the loss of V5+ from the BiVO4 lattice by dissolution. Any composition change caused by the anodic photocorrosion of BiVO4 must be coupled with the oxidation of one or more of the elements present in BiVO4. Since V5+ in the BiVO4 lattice cannot be further oxidized, the dissolution of V5+ must be linked with the photooxidation of Bi3+ and/or lattice O2- ions. We show that the use of a V5+-saturated electrolyte, which inhibits the photooxidation-coupled dissolution of BiVO4, can slow down the rate of photocorrosion considerably and serve as a simple yet effective method to suppress anodic photocorrosion of BiVO4. We also discovered that the V5+ species in the solution can incorporate into the oxygen evolution catalyst (OEC) layer present on the BiVO4 surface during water oxidation, further enhancing water oxidation kinetics. The effect of the V5+ species in the electrolyte on both the long-term photostability of BiVO4 and the performance of the OEC layer will be discussed in detail.