Reduction of CO2 by adsorption and reaction on surface of TiO2-nitrogen modified photocatalyst

• Interaction between the CO2 molecules and TiO2/N-100 occurs chemisorption mechanism.
• TiO2/N-100 reflected in higher yield methanol production in water under UV–vis radiation.
• Maximal methanol production rate was equal to 23 μmol h−1 g−1.

TiO2/N-100 photocatalyst was synthesized by hydrothermal reaction of amorphous anatase TiO2 and NH4OH at 100 °C. The photocatalyst was characterized by FE-SEM, XRD, nitrogen content using elemental analyzer, UV–vis/DR spectroscopy and N2 adsorption at liquid nitrogen temperature. CO2 adsorption up to 30 bar was also investigated. The amount of CO2 adsorbed on TiO2/N-100 was 120 mg g−1 at pressure of 30 bar and temperature of 338 K, which was larger than that on commercially available TiO2 P25. The adsorption isotherm of CO2 on TiO2/N-100 can be well described by the Freundlich adsorption equation. On the basis of n value it was found that an interaction between CO2 molecules and TiO2/N-100 surface occurs according to chemisorption mechanism. The photocatalytic properties of the prepared material were determined in the synthesis of methanol from CO2 in an aqueous solution. The maximum yield of methanol was equal to 20 μmol/g. The maximal methanol production rate was equal to 23 μmol h−1 g−1 and was higher than values reported in the literature by most of authors.

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