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

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