Structural Monitoring of NiBi Modified BiVO4 Photoanodes Using in Situ Soft and Hard X-ray Absorption Spectroscopies

Abstract

Photoelectrochemical (PEC) water splitting, a process using solar light and a semiconductor to split water, is proposed as a potentially scalable method to store solar energy through renewable H2 fuels. Obtaining the electronic structure information on co-catalyst is a crucial step toward gaining a mechanistic understanding of the water oxidation reaction of this catalyst. In the present work, we show that the PEC performance of BiVO4 photoanodes can be enhanced by the deposition of a nickel–borate co-catalyst layer (NiBi). We investigate the electronic structure of the NiBi by in situ soft and hard X-ray absorption spectroscopies (XAS) at the Ni L- and K-edges as well as at the O K-edge under different potential and illumination conditions. We discuss the involvement of the active oxygen species related to the hybridized O 2p Ni 3dt2g orbitals in the oxygen evolution reaction (OER) and further correlate the changes at the O K-edge with that of at the Ni L-edge. In situ soft XAS measurements show that Ni ...