Alkaline Co(OH)₂-Decorated 2D Monolayer Titanic Acid Nanosheets for Enhanced Photocatalytic Syngas Production from CO₂

The difficulty of adsorption and activation of CO2 at the catalytic site and rapid recombination of photogenerated charge carriers severely restrict the CO2 conversion efficiency. Here, we fabricate a novel alkaline Co(OH)2-decorated ultrathin 2D titanic acid nanosheet (H2Ti6O13) catalyst, which rationally couples the structural and functional merits of ultrathin 2D supports with catalytically active Co species. Alkaline Co(OH)2 beneficially binds and activates CO2 molecules, while monolayer H2Ti6O13 acts as an electron relay that bridges a photosensitizer with Co(OH)2 catalytic sites. As such, photoexcited charges can be efficiently channeled from light absorbers to activated CO2 molecules through the ultrathin hybrid Co(OH)2/H2Ti6O13 composite, thereby producing syngas (CO/H2 mixture) from photoreduction of CO2. High evolution rates of 56.5 μmol h–1 for CO and 59.3 μmol h–1 for H2 are achieved over optimal Co(OH)2/H2Ti6O13 by visible light illumination. In addition, the CO/H2 ratio can be facilely tuned from 1:1 to 1:2.4 by changing the Co(OH)2 content, thus presenting a feasible approach to controllably synthesize different H2/CO mixtures for target applications.