Titanium Oxide Thin Films With Metal Nanodisks as Plasmonic Metamaterial Photocatalyst Sheets for IPA‐Assisted CO 2 Reduction

Plasmonic metals are considered a promising approach for enhancing the reactivity of solar‐driven photocatalysts when used as co‐catalytic nanostructures. However, optimizing the energy conversion efficiency is challenging because it requires precise control of the light‐matter interactions at the nanoscale. In this work, we present metamaterial photocatalyst sheets that combine titanium dioxide (TiO 2 ) thin films and plasmonic metal nanodisks arranged in periodic arrays. Silver (Ag), gold (Au), platinum (Pt), and palladium (Pd) were used as nanodisk metals. We tested our photocatalyst sheets for generating solar fuels hydrogen (H 2 ) and methane (CH 4 ) from carbon dioxide (CO 2 ) using steamed water (H 2 O) mixed with isopropyl alcohol (IPA) as a sacrificial agent under broadband (UV–vis–NIR) light exposure. Our Pt/TiO 2 and Pd/TiO 2 photocatalysts achieved gas product rates of 4.37 µmol cm −2 h −1 for H 2 and 0.42 µmol cm −2 h −1 for CH 4 . The fabrication process flow is based on standard semiconductor fabrication methods, showing its potential for large‐scale applications.