High-Throughput Discovery of Earth-Abundant Cu-TiO2 Photocatalysts for Visible-Light Carbohydrate Reforming

Abstract

Using a developed parallelized solid-dispensing platform, we screened in situ modified TiO₂ photocatalysts for visible-light-driven carbohydrate reforming coupled with hydrogen evolution. Across eleven monometallic and eighteen bimetallic catalyst combinations, Cu-TiO₂ emerged as the most promising earth-abundant system. Expanded screening of Cu-TiO₂ across seven simple carbohydrates, three polysaccharides, three fruit juices, and two forms of cotton revealed strong donor-dependent reactivity, with maltose and cellulose yielding the highest hydrogen evolution among the soluble sugars and complex carbohydrates, respectively. Photon-normalized and mass-normalized activity metrics derived from ferrioxalate actinometry contextualize donor performance under visible-light irradiation. Glycerol was used to probe the oxidation half-reaction, and post-illumination analysis identified several established oxidation products, supporting coupled substrate oxidation during H₂ formation. XPS and Auger spectroscopy revealed that photodeposition yields a mixed-valence copper surface layer (Cu⁰/Cu⁺/Cu²⁺). UV–vis-NIR extinction and Tauc analysis demonstrated that Cu incorporation narrows the indirect band gap to enhance visible-light absorption. These results establish Cu-TiO₂ as a promising earth-abundant photocatalyst for biomass-coupled hydrogen evolution and show how parallelized screening can accelerate catalyst discovery and reveal structure-reactivity relationships in heterogeneous photocatalysis.