MgO- and Pt-Promoted TiO2 as an Efficient Photocatalyst for the Preferential Reduction of Carbon Dioxide in the Presence of Water

Abstract

The photocatalytic reduction of carbon dioxide with water to fuels and chemicals is a longstanding challenge. This article focuses on the effects of cocatalysts and reaction modes on photocatalytic behaviors of TiO2 with an emphasis on the selectivity of photogenerated electrons for CO2 reduction in the presence of H2O, which has been overlooked in most of the published papers. Our results clarified that the reaction using H2O vapor exhibited significantly higher selectivity for CO2 reduction than that by immersing the photocatalyst into liquid H2O. We examined the effect of noble metal cocatalysts and found that the rate of CH4 formation increased in the sequence of Ag < Rh < Au < Pd < Pt, corresponding well to the increase in the efficiency of electron–hole separation. This indicates that Pt is the most effective cocatalyst to extract photogenerated electrons for CO2 reduction. The selectivity of CH4 in CO2 reduction was also enhanced by Pt. The size and loading amount of Pt affected the activity; a sma...