Improving performance of water oxidation photoanodes with nanoparticle-polymer hybrid films: Enhanced light-harvesting and catalytic efficiency

Abstract

Solar water oxidation has received great attention as an efficient way to convert unlimited solar energy into chemical energy for sustainable development. Theoretically, it can be achieved by using a semiconducting material with a suitable bandgap and band-edge positions. Despite considerable efforts for several decades, most semiconducting materials have low photocatalytic performance due to their inherent limitations such as narrow absorption band with a low absorption coefficient, fast recombination of photogenerated excitons, sluggish water oxidation kinetics, and photocorrosion. To address these problems, it is important to develop a comprehensive strategy to modify them with proper functional materials. In this study, we report the development of an efficient water oxidation photoanode (e.g., Fe O and BiVO ) through the integration of various functional substances on their surface using layer-by-layer (LbL) assembly techniques. Various polyelectrolytes were used as an electrostatic adhesive to integrate the following functional materials: plasmonic Ag nanoparticles (NPs), upconversion (UCN) NPs, and polyoxometalate (POM) water oxidation catalysts (WOCs). After the modification with these components, the performance of water oxidation photoanodes was significantly enhanced due to their respective roles: (1) improved light harvesting by effective electron extraction in the band absorption region by Ag NPs, (2) utilization of infrared light by UCN NPs, (3) suppression of surface recombination with polyelectrolyte passivation layers, and (4) increased catalytic activity by POM WOCs. We believe that our approach can provide insights to design and application of LBL-assembled novel electrochemical and otoelectrochemical devices.