Adsorption of CO₂ on Amorphous and Crystalline Zirconia: A DFT and Experimental Study

Abstract

Herein, we study the structural and electronic origins of molecular adsorption using experiments and density functional theory (DFT) calculations. We performed X-ray diffraction (XRD) and temperature-programmed desorption (TPD) of CO2 on amorphous zirconia (am-ZrO2) and crystalline (tetragonal and monoclinic) zirconia. Using molecular dynamics simulations, the bulk structures of am-ZrO2 and am-zirconium(IV) hydroxide (am-Zr(OH)4) were obtained and the reproducibility of the experimental structure was confirmed by comparing the radial distribution functions. In addition, the hydroxyl density on the hydrogenated ZrO2 surfaces was found to be consistent with the experimental results. Both experiments and simulations indicate that the adsorption of CO2 on an am-ZrO2 surface is more heterogeneous and weaker than that on a crystalline zirconia surface. Because the charge environment and band structures of crystalline zirconia are approximately the same as those of am-ZrO2, the weak adsorption on the am-ZrO2 surface arises from the fewer and stronger Zr–O bonds on the surface. These findings provide molecular-level insight not only for the adsorption of CO2 but also into the molecular adsorption on ZrO2-based catalysts.

Low-Temperature CO2 Methanation over Ru Nanoparticles Supported on Monoclinic Zirconia

“…This discrepancy can be explained by the differences in the CO 2 adsorption ability. Previously, we examined the relationship between the crystal structure of ZrO 2 and the CO 2 adsorption ability through experimental and computational chemistry . Our findings revealed that CO 2 molecules are strongly adsorbed, or easily activated, on m-ZrO 2 compared to amorphous ZrO 2 .…”

“…In this study, we evaluated the performance of the catalysts using crystallized ZrO 2 as a support. Through combined experimental and computational approaches, it is shown that CO 2 molecules are more strongly adsorbed on crystalline ZrO 2 than on am-ZrO 2 ; in other words, crystalline ZrO 2 may efficiently activate CO 2 molecules. Herein, several types of Ru/m-ZrO 2 (m-: monoclinic) were prepared via incipient wetness impregnation and selective deposition methods, and the influence of the preparation methods on CO 2 methanation over Ru/m-ZrO 2 was investigated.…”

Difference in reaction mechanism between ZnZrOx and InZrOx for CO2 hydrogenation

“…First, we measured the specific surface area (SSA) and total pore volume by N 2 adsorption (Table 1). The SSA of ZnZr46, InZr09, and InZr22 is lower than that of amorphous ZrO 2 (approximately 200 m 2 g −1 ), 35 which is the raw material. This result was attributed to sintering at 500 °C during catalyst preparation.…”

“…The Zr atoms on the surface are classified into two types, and the replaced Zr atom acts as a strong Lewis site with longer Zr–O bonds. 34,35 Fig. S1 (ESI†) shows the positions of In and one oxygen vacancy (V O ).…”

A Detailed Comparative Analysis of the Structural Stability and Electron-Phonon Properties of ZrO2: Mechanisms of Water Adsorption on t-ZrO2 (101) and t-YSZ (101) Surfaces

“…First-principles (ab initio) methods within the framework of DFT are successfully used in modern materials science regarding condensed matter physics [39][40][41][42][43][44][45][46][47][48].…”