Ultrathin porous g-C3N4 nanosheets modified with AuCu alloy nanoparticles and C-C coupling photothermal catalytic reduction of CO2 to ethanol

Schematic PTCR conversion of CO2 to ethanol via the AuCu/g-C3N4 to achieve carbon cycle. [Display omitted] •AuCu/g-C3N4 composite was constructed with the aid of seed crystal mediated method.•Ultrathin porous g-C3N4 nanosheets promotes rivet of AuCu NPs and accelerates carrier migration.•AuCu can quicken charge separation, and synergistic effect promote C-C coupling to ethanol.•Thermal accelerates the movement of *CO and promotes the formation of ethanol by C-C coupled process.•We provide efficient method of converting CO2 to ethanol by combination of AuCu alloy and g-C3N4. Here, we report ultrathin porous g-C3N4 nanosheets modified with AuCu alloy NPs for photothermalcatalytic CO2 reduction to ethanol. The positive charge on the Au surface improves the adsorption of CO2 molecules and the charge transfer from Au to Cu in the alloy enriches Cu with excessive negative charges, promoting the formation of intermediates CO2·- and *CO on the surface of Cu. The strong interaction between the metal and g-C3N4 accelerates the migration of photogenerated charges. The increase of temperature leads to the enhancement of the thermal motion of the molecules, resulting in the synergy of photocatalysis and thermal catalysis, which promotes the formation of C-C coupling by *CO polymerization, so that the yield of CH3CH2OH was increased. At 120 ℃, the yield and selectivity of ethanol are 0.89 mmol·g−1·h−1 and 93.1% for 1.0 wt% AuCu/g-C3N4, which are 4.2 times that of photocatalysis and 7.6 times that of thermal catalysis.