Engineering the TiO2 outermost layers using magnesium for carbon dioxide photoreduction

•TiO2–Mg photocatalysts were synthetized by sol–gel method.•The introduction of magnesium leads to a modification of the TiO2 surface, by the creation of Ti3+ and OS.•CO2 photoreduction yield has a straightforward correlation with density of Ti3+ and OS.•For low amounts of additive, it was found a 4.5 fold enhancement towards CH4 formation.

Magnesium modified TiO2 photocatalyst has been found to improve the CO2 photoreduction reaction, with a high selectivity towards CH4. Thus, Mg–TiO2 has been synthesized with different compositions up to 2.0 wt%. Unlike the bare TiO2, the surface reorganization originated by the presence of Mg enhances the formation of methane by a factor of 4.5, corroborating that complete reduction of CO2 is achieved. It was found that the enhancement of the overall photocatalytic activity towards carbon dioxide reduction can be increased by a factor of 3, revealing a straightforward correlation with the surface states induced by the presence of the doping element. Finally, the evolution of the selectivity versus methane formation against hydrogen is discussed for the different magnesium loadings.

Graphical abstractCO2 photoreduction yield on Mg–TiO2 has a straightforward correlation with density of Ti3+ and OS at the surface induced by the presence of Mg2+, achieving an unprecedented selectivity towards CH4.Figure optionsDownload full-size imageDownload as PowerPoint slide