2020/09/10 by Feng Jiang, Shanshan Wang, Bing Liu +5 · 2 citations
Materials Science · Chemical Engineering · #Catalytic Processes in Materials Science #Catalysts for Methane Reforming #Carbon dioxide utilization in catalysis
paper · doi:10.1021/acscatal.0c03324
openalex publication_date 2020/09/10 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
CeO 2 is an excellent potential material for CO 2 hydrogenation attributed to the highly tunable properties including metal–support interaction and abundant oxygen vacancy. In this work, four CeO 2 supports with structurally well-defined different shapes and crystal facets are hydrothermally prepared, and their effects on the composition of Pd species and oxygen vacancy over Pd/CeO 2 catalysts have been intensively investigated in the reduction of CO 2 to methanol. The 2Pd/CeO 2 -R (rods) shows the highest concentration and number of oxygen vacancies, where the (110) facet with high surface oxygen mobility and low oxygen vacancy formation energy is exposed over the CeO 2 -R surface. The oxygen mobility at the interface of (111) and (100) facets mainly observed on 2Pd/CeO 2 -P (polyhedrons) is higher than the single (111) and (100) facets mainly observed on 2Pd/CeO 2 -O (octahedrons) and 2Pd/CeO 2 -C (cubs), respectively. The presence of Pd highly promotes the formation of oxygen vacancies by providing dissociated H atoms to facilitate the removal of surface O in ceria support under a H 2 atmosphere. Both the Pd x Ce 1– x O δ solid solution dominated on CeO 2 -R and the PdO species dominated on CeO 2 -O are reduced to metallic Pd after reduction with 6–10 nm average particle size. As revealed by density functional theory (DFT) calculations, in contrast to the single Pd 0 atom on CeO 2 and the thermodynamically most unstable Pd x Ce 1− x O δ solid solution, the Pd 0 nanoparticles are the most stable species under the realistic reaction conditions. The 2Pd/CeO 2 -R shows the highest catalytic activity as the abundantly available oxygen vacancies function as CO 2 adsorption and activation sites. Moreover, oxygen vacancy reactivity is correlated with its formation energy. The lower formation energy facilitates the formation of oxygen vacancy; however, the reactivity of each oxygen vacancy is lower as the TOF oxygen vacancy of 2Pd/CeO 2 -O is 15 times as that of 2Pd/CeO 2 -R. Thus, a suitable oxygen vacancy formation energy is likely favorable for enhancing CO 2 reactivity. DFT calculations indicate that the CH 3 OH formation is most probably from the formate (HCOO*) pathway via the C–O bond cleavage in H 2 COOH*, with the reduction of HCOO* to HCOOH* as the rate-limiting step. These results would provide experimental and theoretical insights into the rational design of an effective catalyst for CO 2 hydrogenation.