Crystal-Plane Effects of CeO₂{110} and CeO₂{100} on Photocatalytic CO₂ Reduction: Synergistic Interactions of Oxygen Defects and Hydroxyl Groups

Abstract

For photocatalytic CO 2 reduction, the synergistic effect of Lewis acidity and basicity on CO 2 activation is worthy of study. On the basis of a large number of oxygen defects (Lewis acidity) and hydroxyl groups (Lewis basicity) on the CeO 2 surface, CeO 2 {110} and CeO 2 {100} crystal planes were developed to investigate the synergistic effect on photocatalytic CO 2 reduction. Compared with CeO 2 {100}, the surface oxygen defects were prone to generate on CeO 2 {110}, leading to available visible light absorption and faster photogenerated charge transfer. The experimental results and DFT calculations showed that the OH species on the CeO 2 {110} surface were richer and provided more electron density, i.e., Lewis basicity. Furthermore, the possible adsorption intermediate was investigated and suggested that CeO 2 {110} was more beneficial for the adsorption and activation of CO 2 reactant than CeO 2 {100}, resulting in generation of carboxylate species and •CO 2 − radicals, instead of carbonate. Under the control of surface Lewis acidity and basicity, CeO 2 {110} had superior photocatalytic performance of CO 2 reduction than the {100} plane.

Role of Anions in the Synthesis and Crystal Growth of Selected Semiconductors

“…Apart from that, Cl − directs the growth of particles into tube-like or wire-like particles. This is similar to rod-like structure however, the synthesis conditions such as temperature, acidity, and basicity as well as the use of capping agents leads to the distortion of the rod shape of particles ( Samiee and Goharshadi, 2012 ; Zhu et al, 2020 ; Zhang et al, 2021 ).…”

“… Zhu et al (2020) synthesized CeO 2 using Ce(NO 3 ) 3 ·6H 2 O and CeCl 3 ·7H 2 O in hydrothermal reaction for photocatalytic CO 2 reduction. The synthesis was carried out at 140 and 180°C producing CeO 2 nanocubes of about 30 nm length and nanorod of 200–400 nm in length and 20 nm in diameter when Ce(NO 3 ) 3 ·6H 2 O and CeCl 3 ·7H 2 O were used, respectively.…”

“…Interestingly, when NO 3 − salts were introduced, the morphology of the metal oxides was directed into faceted shaped MO (cube, plate-like, hexagonal, honeycomb, etc.) ( C. Nehru et al, 2012 ; Jayakumar et al, 2022 ; Wang et al, 2010 ; Panda et al, 2013 ; Zhu et al, 2020 ). Typically, metal oxides form polyhedral-kind of shape and in order to tune the surface free energies and induce the anisotropic growth of well-shaped nanostructures, adscititious surfactants are required in which this is the case for most of the reported shapes ( Table 1 ) ( Yang and Gao, 2006 ).…”

Probing the morphological effects of ReOx/CeO2 catalysts on the CO2 hydrogenation reaction

“…[13][14][15] The catalytic performance can be influenced by adsorbed intermediate species, and their adsorption strength or sites. Density functional theory (DFT) calculations found that oxygen vacancies were crucial for the adsorption and stabilization of reactive species, 16 and CO 2 was readily adsorbed as carbonate (CO 3 2− ) near oxygen vacancy sites on the CeO 2 (111) surface. In contrast, the preferable adsorbate on the oxygen vacancies of the CeO 2 (110) facet is the carboxylate species (CO 2 δ− ).…”

“…In contrast, the preferable adsorbate on the oxygen vacancies of the CeO 2 (110) facet is the carboxylate species (CO 2 δ− ). 16 We have also investigated the relationship between the CO 2 chemisorption states and the CO 2 hydrogenation activity based on a Zn-Cr mixed-oxide catalyst. 1 The oxygen-deficient catalyst which adsorbed CO 2 as CO 2 δ− showed a higher hydrogenation activity compared to the oxygen-rich catalyst which chemisorbed CO 2 as CO 3 2− .…”