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[Display omitted] • The low-cost Cu 2 O/g-C 3 N 4 heterojunction is constructed by simple hydrothermal method. • Cu 2 O/g-C 3 N 4 exhibited synergistic effects of thermalcatalysis and photocatalysis. • The overpotential reduce by 0.34 V in ILs than KHCO 3 electrolyte. • We provided strategy of CO 2 reduction to ethanol assisted by ILs under thermal field. Photocatalytic CO 2 reduction is a potential way to address simultaneously environmental pollution and energy shortage. However, the difficulties of CO 2 activation and C C coupling lead to quite low conversion efficiency of CO 2 to C2 products. In this study, we constructed Cu 2 O/g-C 3 N 4 heterojunction for photocatalytic CO 2 reduction to ethanol by coupling thermal field and ionic liquids (ILs). The ethanol rate reached 0.71 mmol·g−1·h−1 over Cu 2 O/g-C 3 N 4 under photothermalcatalysis, which is 1.89 times that of photocatalysis and 7.05 times that of thermal catalysis. The temperature enhanced thermal motion of the radical, which promotes the formation of ethanol through the ·CH 3 dimerization. The 1-aminopropyl-3-methylimidazolium bromide ILs shows superior CO 2 reduction performance with a high current density (21.3 mA·cm−2) than KHCO 3 electrolyte (12.8 mA·cm−2). The overpotential is reduced by 0.34 V, which accelerates CO 2 reduction by reducing polarization. It is found that the ILs played a key role in suppressing H 2 O reduction and increasing ethanol yield in this photothermalcatalytic strategy. [ABSTRACT FROM AUTHOR]

Ultrathin TiO 2 nanosheet with abundant Ti3+ is constructed as a photocatalyst for CO 2 conversion in the absence of any sacrificial reagents. The exposed Ti3+ as a Lewis base site may activate CO 2 to form bridging Ti···CO 2 −···Ti, resulting highly CH 4 yield via the synergistic effect of coordination-activation and photocatalysis. • Ultrathin TiO 2 nanosheets (NST) with abundant Ti3+ sites are constructed as a photocatalyst for conversion CO 2. • The catalyst (NST) exhibits a high yield (147.2 μmol g−1 h−1) and selectivity (96.8 %) for CH 4. • CO 2 would be selectively activated on the surface of NST via forming the bridging Ti···CO 2 −···Ti coordination species. • The synergistic effect about coordination-activation and photocatalysis can greatly enhance CH 4 yield efficiency. Ultrathin TiO 2 nanosheet (NST) with abundant Ti3+ sites is developed as a photocatalyst which exhibits a high yield (147.2 μmol g−1 h−1) and selectivity (96.8%) for CO 2 to CH 4. The results of in situ FTIR, in situ EPR and density functional theory (DFT) calculation suggest that CO 2 would be selectively activated on NST surface via forming the bridging Ti···CO 2 −···Ti coordination species which not only lowers the activation energy barrier, but also determines the selectivity of CH 4. Additionally, NST with the better separation and transfer ability for photogenerated electrons-holes can fleetly supply the electrons to CO 2 molecules for high efficiently producing CH 4 via the Ti-C coordination bond. Finally, a possible mechanism of the synergistic effect about coordination-activation and photocatalysis is discussed at a molecule level. This work would offer a perspective for designing an effective photocatalyst and tailoring the selectivity of products by coordination activation. [ABSTRACT FROM AUTHOR]