Nitrogen-Doped Ni/TiO2 Catalyst with Enhanced Activity and Improved Selectivity for CO2 Methanation

The construction of efficient catalysts is still the bottleneck for the industrialization of CO2 methanation. Herein, a nitrogen (N)-doping strategy was developed to boost both activity and selectivity of the Ni/TiO2 catalyst, wherein N-doped TiO2 was prepared by a mild sol–gel method and employed as the support for Ni catalysts. In detail, CO2 conversion at 350 °C over the Ni/TiO2 and Ni/N10-TiO2 catalysts was 9.6 and 41.7%, respectively. CH4 selectivity at 400 °C over the Ni/TiO2 and Ni/N10-TiO2 catalysts was 44.1 and 84.6%, respectively. In comparison to the undoped Ni/TiO2 catalyst, the Ni/N10-TiO2 catalyst had a smaller Ni size and enriched basic sites, leading to enhanced activity. The introduction of N dopants transformed TiO2 phases from anatase into rutile and induced intimate contact between Ni nanoparticles and rutile TiO2, resulting in improved CH4 selectivity. Substituted, interstitial, and oxidized N species were detected on the surface of N-doped Ni/TiO2 catalysts, among which substituted N was identified as the most critical species. The present work provides a facile and feasible strategy to promote both activity and selectivity of supported catalysts in CO2 hydrogenation.