Micro-kinetic modelling of photocatalytic CO2 reduction over undoped and N-doped TiO2

Abstract

CO₂ photoreduction is studied using in-house synthesized undoped and N-doped TiO₂ nanoparticle photocatalysts. Comparison with the commercial P25 TiO₂ powder shows that the synthesized samples are more effective. P25 produced a negligible amount of CH₄, unlike the synthesized samples. N-doping of TiO₂ powder caused a higher productivity rate of all products, and provided the best performance for CO₂ reduction. The average production rate of CH₄ was 0.191 μmol h⁻¹ g⁻¹, whereas that of CO was 0.111 μmol h⁻¹ g⁻¹. The experimental data are used to fit the micro-kinetic modelling parameters. The kinetic constant of H₂O dissociation is the lowest for all tested samples, revealing that this is the rate-determining step. The kinetic constants for the H₂, CO, and CH₄ formation were of the same order for all catalyst samples, showing that the rates of these reactions are independent of the catalyst type.