Highly Stable and Selective Ni/ZrO 2 Nanofiber Catalysts for Efficient CO 2 Methanation.

Ni-based oxides are promising catalysts for CO 2 methanation. However, Ni-based catalysts also have some unresolved issues and drawbacks in practical applications. The activity and selectivity of Ni-based catalysts in CO 2 methanation at low temperatures still need to be improved. Here, Ni/ZrO 2 nanofibers with high surface areas (up to 101.2 m 2 /g) were prepared by electrospinning methods. The Ni/ZrO 2 -ES (also named as 66Ni/ZrO 2 ) catalyst showed excellent catalytic performance in CO 2 methanation (the CO 2 conversion = 81% and CH 4 selectivity = 99% at 350 °C) and excellent stability for 100 h, which was better than most reported Ni/ZrO 2 catalysts. However, the comparison sample Ni/ZrO 2 -CP prepared by the coprecipitation method had poor catalytic performance (the CO 2 conversion = 54% and CH 4 selectivity = 90% at 350 °C). Within 100 h, the CO 2 conversion decreased to 30% and the CH 4 selectivity decreased to 52%. Both EPR and O 1S XPS confirmed that Ni/ZrO 2 nanofibers can form more reactive oxygen species vacancies, and CO 2 -TPD confirmed that nanofibers had more CO 2 adsorption sites compared with the control sample Ni/ZrO 2 -CP. In situ DRIFTS analysis showed that bidentate carbonate and monodentate carbonate were key intermediates in CO 2 methanation. The catalytic performance of Ni/ZrO 2 nanofiber catalysts would be attributed to higher dispersion of Ni species on the surface of nanofibers, high specific surface area (101.2 m 2 /g), more oxygen vacancies, more CO 2 adsorption sites, and the synergistic effect between Ni nanoparticles and ZrO 2 nanofibers. This work may inspire the rational design of Ni/ZrO 2 nanofiber catalysts with rich oxygen vacancies for low-temperature CO 2 methanation.