Stable Ni-decorated CaTiO3/WO3/BiVO4 multi-layered photoanodes for improved solar-driven water oxidation at high current densities

Abstract

Conventional electrochemical systems involving the oxygen evolution reaction (OER) in the anodic compartment suffer from low efficiency and high energy consumption, accounting for over 90 % of the total energy input, thereby hindering the practical application of this technology. The reliance on external energy can be decreased by coupling external renewable energy sources, such as solar energy, through a sustainable photoelectrochemical (PEC) approach driven by efficient photoanodes. In this study, we present the automated fabrication and optimization of multi-layered Ni-decorated CaTiO3/WO3/BiVO4 photoanodes, supported onto FTO substrates, for enhanced PEC water oxidation under visible-light illumination. Different photoanode configurations are fabricated via layer-by-layer deposition, with the top layer consisting of either sequentially deposited Ni and BiVO4 layers or a physical mixture of the two materials. The mixed Ni-BiVO4 top layer configuration strengthens the synergistic interaction between components, resulting in enhanced PEC performance with a cathodic potential as low as −1.17 V vs. Ag/AgCl at a practically relevant current density of 100 mA cm−2. Furthermore, the applied bias photon-to-current efficiency (ABPE) for this optimized photoanode configuration reaches a maximum of 0.52 %, corresponding to an O2 production rate of 2 μmol cm−2 h−1 under visible light (100 mW cm−2). Overall, this work demonstrates how optimizing multi-layered photoanodes enables operation at current densities relevant for practical applications, paving the way for their integration in PEC systems.