Emerging Oxide-Based Light Harvesters for Bias-Free Water and CO₂ Splitting

Oxides have long been investigated for solar water splitting, but generally have wide bandgaps beyond the visible wavelength range. As such, there have been efforts to tune the species at the cation and anion sites to lower the bandgap. This presentation will explore two nontoxic bismuth-based compounds part of the wider oxide-based family: bismuth oxyiodide (BiOI) and bismuth vanadate (BiVO₄). Whilst BiVO₄ is a well-established visible light absorber for photoanodes, BiOI has only had a handful of investigations as photocathodes, partly because of its degradation when used in semiconductor-electrolyte junctions. In this work, we develop inorganic charge transport layers sandwiching the BiOI light absorber, and combine with conducting encapsulants to improve the stability of BiOI photocathodes from minutes to months. By working in tandem with BiVO₄ photoanodes, we achieve photoelectrochemical tandems capable of bias-free syngas (CO + H₂) and H₂/O₂ production, which we show to be stable for hundreds of hours. Furthermore, we demonstrate that fabricating large-area devices from a combination of pre-selected pixels leads to improved performance over the use of a single large-area pixel, and is a promising route to scaling up these photoelectrochemical tandems. This talk finishes with a discussion of the potential of materials from the wider family of perovskite-inspired materials as the light harvesters for solar water splitting.<br/><br/>Andrei, Jagt, … MacManus-Driscoll,* Hoye,* Reisner,* <i>Nat. Mater.</i>, 2022, <i>21</i>, 864