P25@CoAl layered double hydroxide heterojunction nanocomposites for CO 2 photocatalytic reduction

Delaminated CoAl‐Layered Double Hydroxide@TiO2 Heterojunction Nanocomposites for Photocatalytic Reduction of CO2

“…The DRUV spectrum of CoAl‐LDH exhibited two distinct absorption bands, a broad band in the visible region centered around 558 nm, and a sharper UV band around 300 nm; delamination shifted the middle band to ≈520 nm, and resulted in the appearance of additional absorption band around 670 nm. The bands 520–558 nm are indicative of the 4T1g(F) →4T1g(P) transition of Co 2+ octahedrally coordinated by weak‐field ligands, while that at 670 nm band corresponds to a 3A2g(F)→3T1g(F) transition arising from spin–orbit coupling . The UV absorption may arise from ligand → metal charge transfer within the CoAl‐LDH layer.…”

“…The photocatalytic performance of CoAl‐LDH@TiO 2 nanocomposites was subsequently investigated for aqueous phase CO 2 reduction under UV–vis irradiation by a 300 W Xe lamp in the absence of a sacrificial hole acceptor. Control experiments were first performed in the absence of either CO 2 , water, catalyst, or light (Figure S15, Supporting Information) to confirm that CO 2 and water were the only sources of carbon and hydrogen in photocatalytic products . Only gaseous products of photocatalysis were observed, namely CO 2 , H 2 , O 2 , and (exceptionally) methane.…”

“…We therefore recently synthesized a nanocomposite photocatalyst for aqueous CO 2 photocatalytic reduction, comprising commercial P25 titania in contact with a CoAl‐LDH. This exhibited promising activity (2.2 µmol g –1 h –1 ) and >80% selectivity to CO, without requiring a sacrificial hole scavenger . The superior performance of this type‐II heterojunction photocatalyst was attributed to increased photoexcited charge carrier lifetimes relative to its individual UV and visible light absorbing semiconductor components, attributed to the spatial separation of charge carriers due to electron transfer from CoAl‐LDH → P25, and concomitant hole transfer from P25 → CoAl‐LDH, and extended utilization of the solar spectrum.…”

“…Herein, the preceding design strategy is extended through the synthesis of new heterojunction nanocomposites comprising delaminated CoAl‐LDH nanosheets dispersed within matrices of high aspect TiO 2 nanoparticles (NPs) or nanotubes (NTs). These nanocomposites enable decoupling of the relative importance of the dimensions/morphology of the visible light (hole‐driven) CoAl‐LDH and UV light (electron‐driven) TiO 2 semiconductors for CO 2 photocatalytic reduction. CoAl‐LDH thickness and titania morphology both strongly influence aqueous CO 2 reduction, with the combination of delaminated CoAl‐LDH nanosheets with TiO 2 nanotubes delivering 4.57 (2.0) µmol g cat –1 h –1 of CO and 0.41 (0.1) µmol g cat –1 h –1 of CH 4 under UV–vis (or visible) irradiation, through a stoichiometric redox process and in the absence of sacrificial agents.…”

Stability and Synergistic Effect of Polyaniline/TiO2 Photocatalysts in Degradation of Azo Dye in Wastewater

“…Furthermore, titanium dioxide (TiO 2 ) is one of the most commonly used commercial photocatalysts, as it is non-toxic, low in cost and environment friendly, due to its chemical stability [3,4,5]. However, the relatively high band gap (3.2 eV) of TiO 2 [6] restricts its photocatalytic activity under visible light (Vis), whereas its poor quantum efficiency, due to recombination of electrons (e CB − ) and holes (h VB + ) [7], is another disadvantage. …”