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

Abstract

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.