Synthesis of 3D ordered macroporous TiO2-supported Au nanoparticle photocatalysts and their photocatalytic performances for the reduction of CO2 to methane

• 3DOM TiO2-supported Au nanoparticles were facilely synthesized by the GBMR method.
• The slow light effect of the 3DOM structure can enhance absorption efficiency of solar irradiation.
• The SPR effect of Au nanoparticles can effectively enhance the visible spectral response.
• Au NPs in 3DOM Au/TiO2 catalysts improve the separation of photogenerated electron–hole pairs.
• The catalysts show high activity for reduction of CO2 to CH4 under visible light irradiation.

This work presents the design and preparation of three-dimensionally ordered macroporous (3DOM) TiO2-supported Au nanoparticles with enhanced visible-light-responsive properties for the application in carbon dioxide (CO2) photoreduction. The 3DOM TiO2 support was prepared using a colloidal crystal template (CCT) method. A series of photocatalysts of TiO2-supported Au nanoparticles with uniform sizes were successfully synthesized by the facile method of gas bubbling-assisted membrane reduction (GBMR). These photocatalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy, Brunauer–Emmet–Teller (BET) analysis of nitrogen adsorption isotherm, photoluminescence spectra (PL), and the surface photovoltage (SPV) technique. All the catalysts possess well-defined 3DOM structures, which are highly ordered and interconnected with one another by small pore windows, and the Au nanoparticles are uniformly dispersed and supported on the inner wall of the uniform macropores. The slow light effect of the 3DOM structure can enhance absorption efficiency of solar irradiation. And the introduction of Au nanoparticles can effectively extend the spectral response from UV to visible region owing to Au surface plasmon resonance (SPR), and it is favorable for enhancing the separation of photoinduced electron–hole pairs. 3DOM Au/TiO2 photocatalysts exhibit high catalytic activity for the photocatalytic reduction of CO2 with H2O to CH4 under visible illumination.

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