Delaminated CoAl-Layered Double Hydroxide at TiO2 Heterojunction Nanocomposites for Photocatalytic Reduction of CO2

Photocatalytic reduction offers an attractive route for CO2 utilization as a chemical feedstock for solar fuels production but remains challenging due to the poor efficiency, instability, and/or toxicity of current catalyst systems. Delaminated CoAl-layered double hydroxide nanosheets (LDH-DS) combined with TiO2 nanotubes (NTs) or nanoparticles (NPs) are promising nanocomposite photocatalysts for CO2 reduction. Heterojunction formation between visible light absorbing delaminated CoAl nanosheets and UV light absorbing TiO2 nanotubes greatly enhances interfacial contact between both high aspect ratio components relative to their bulk counterparts. The resulting synergic interaction confers a significant improvement in photoinduced charge carrier separation, and concomitant aqueous phase CO2 photocatalytic reduction, in the absence of a sacrificial hole acceptor. CO productivity for a 3 wt% LDH-DS at TiO2-NT nanocomposite of 4.57 μmol gcat -1 h-1 exhibits a tenfold and fivefold increase over that obtained for individual TiO2 NT and delaminated CoAl-LDH components respectively and is double that obtained for 3 wt% bulk-LDH at TiO2-NT and 3 wt% LDH-DS at TiO2-NP catalysts. Synthesis of delaminated LDH and metal oxide nanocomposites represents a cost-effective strategy for aqueous phase CO2 reduction.