Unraveling the Role of Manganese in Enhancing Ni/TiO2 Catalysts for Photothermal CO2 Methanation

The escalating CO 2 concentration and energy demand necessitate efficient CO 2 conversion strategies. Photothermal catalytic CO 2 methanation is a promising strategy, yet its efficiency is hindered by the inherent stability of CO 2 and the rapid recombination of photogenerated charge carriers. Among non-noble metal catalysts, Ni-based catalyst is a promising candidate for CO 2 methanation, with sintering and agglomeration remaining to be addressed. Herein, NiMn/TiO 2 bimetallic catalysts with varying Ni/Mn ratios were synthesized to overcome these issues. Characterization results demonstrate that Mn incorporation enhances CO 2 adsorption capacity by increasing oxygen vacancies and significantly improves the separation efficiency of photogenerated carriers. Furthermore, Mn doping optimizes the electronic structure of the catalyst, narrowing its bandgap for improved light absorption. But the catalytic performance is highly dependent on the Ni/Mn ratio. The synergistic effect of Ni and Mn can be maximized when the Ni/Mn ratio is 1:1, which is specifically manifested as the best catalytic activity. Excessive Mn loading covers active Ni sites and impedes electron transfer, thereby degrading activity. Therefore, this work highlights the importance of Mn as a promoter in designing efficient non-noble metal catalysts for photothermal CO 2 conversion.