Enhanced photocatalytic CO2 reduction to CH4 by Mn2O3/MgTi2O5 nanocomposite

Photocatalysis is a green technology which could sustainably convert CO 2 into value-added chemicals by using solar energy. Under xenon light irradiation, Mn 2 O 3 /MgTi 2 O 5 nanocomposites synthesized by two-step hydrothermal method greatly increase photocatalytic activity of CO 2 reduction. The optimal yield 420.53 μmol g −1 h −1 for CH 4 is achieved at a ratio 1:10 (W/W) of Mn 2 O 3 to MgTi 2 O 5 , with selectivity of 98.1 %, i.e., 4 and 33 times larger than those of individual MgTi 2 O 5 and Mn 2 O 3 , respectively. The superior photocatalytic performance is attributed to the formation of S-type heterojunction, valence change of Mn 3+ /Mn 4+ , and the bridging effect of Mg migration, which facilitates the separation and transfer of photogenerated electrons and holes. Mn 2 O 3 /MgTi 2 O 5 constructs an efficient redox photocatalytic system composed of a light trapping component (Mn 2 O 3 ), electron transport channel (Mg penetrating Mn 2 O 3 ), mutually separated reduction center (MgTi 2 O 5 ) and oxidation center (Mn 2 O 3 ). The potential Mn 2 O 3 /MgTi 2 O 5 photocatalyst for CO 2 reduction provides new insights to design novel efficient photocatalyst composites akin to biological photosynthesis.