Boosting CO2 methanation activity by tuning Ni crystal plane and oxygen vacancy in Ni/CeO2 catalyst
Yingting Liu, Danyang Li, Han Zhao, Chunliang Wang, Xu Yang, Luyao Li, Zhiqiang Li, Hua Wang, Kongzhai Li
Abstract
It is challenging to boost CO 2 methanation activity over Ni-based catalysts, and new findings that decipher the relationship between the essential laws of catalysts and their catalytic performance will be transformative. Herein, three kinds of Ni/CeO 2 catalysts with different Ni crystal facets and oxygen vacancy are developed by varied preparation methods, which show significant differences in catalytic performance for CO 2 methanation, and these catalysts are taken as a case study for the investigation of the crystal plane and oxygen vacancy effects in CO 2 methanation as well. It is observed that the activity of Ni/CeO 2 -SG catalyst with abundant oxygen vacancies and principally exposed Ni (1 1 1) crystal facet is highly active for CO 2 methanation reaction, which is 1–3 times than that of Ni/CeO 2 catalysts with poor oxygen vacancy and/or Ni (1 1 1) crystal face. In addition, the former one cannot suffer from deactivation even in operation 130 h at 300 °C. Both structural investigations and catalytic evaluations indicate that the adsorption and activating ability of H 2 and CO 2 can be controlled by adjusting the Ni-exposed crystal face and oxygen vacancy concentration, respectively. It is also verified that the synergistic contribution of the Ni crystal facets and the oxygen vacancy play a crucial role in boosting the catalytic activity of the Ni/CeO 2 catalysts by affecting the adsorption and activation of reactants. The Ni/CeO 2 catalysts exposed Ni (1 1 1) crystal plane facilitate the catalytic activity by strengthing the H 2 adsorption/dissociation capacity, while the abundantly available oxygen vacancies maximize the activity via acting as CO 2 activation sites. Furthermore, the in situ DRIFT experiments reveal that the direct formate hydrogenation pathway is involved in the CO 2 methanation process over the Ni/CeO 2 -SG catalyst.