Oxygen Vacancy Generation and Stabilization in CeO_2–x by Cu Introduction with Improved CO₂ Photocatalytic Reduction Activity

Abstract

Introducing O vacancies into the lattice of a semiconductor photocatalyst can alter its intrinsic electronic properties and band gap, thus enhancing the visible light absorption, promoting the separation/transfer of photogenerated charge carriers, and resultantly elevating the photocatalytic activity of oxide semiconductors. Moreover, O vacancies can help adsorb and activate CO 2 on photocatalyst surfaces, which, however, are prone to being filled by O atoms during the photoreduction reaction. In this work, Cu was introduced to increase the O vacancy concentration in CeO 2−x and promote the photocatalytic activity of CeO 2−x . The sample Cu/CeO 2−x -0.1 showed the highest photocatalytic activity with a CO yield of 8.25 μmol g −1 under 5 h irradiation, which is ∼26 times that on CeO 2−x . According to the analysis of Raman and X-ray photoelectron spectroscopy (XPS) spectra, it has been evidenced that Cu introduction benefits the chemical stabilization of O vacancies in CeO 2−x during photocatalytic CO 2 reduction, which is responsible for the improved and sustained photocatalytic activity.

Atomic‐Level Reactive Sites for Semiconductor‐Based Photocatalytic CO2 Reduction

“…The synergetic effects of two reactive sites lead to the formation of C 2 products and keeps the oxygen vacancy sustained. The doping of Cu atoms into CeO 2 can introduce stable oxygen vacancies and increase surface basicity that promotes CO 2 chemisorption and photocatalytic performance …”

“…Atomic‐level reactive sites can be introduced into photocatalysts via a range of strategies such as: introducing vacancies in the crystal lattice, doping single heterogeneous atoms, anchoring functional groups and loading metal complexes on the surface, and fabricating FLPs . With advances in characterization technologies and synthesis methods, researchers can design materials from atomic level to reveal fundamental photocatalytic CO 2 reduction from spatial‐and‐time perspectives using, for, e.g., high resolution transmission electron microscope (HRTEM), scanning transmission electron microscopy (STEM), and in situ technologies.…”

“…Vacancies in crystal lattices have received significant attention. For example, oxygen vacancy, sulphur vacancy, nitrogen vacancy, carbon vacancy, and cation vacancies, even dual vacancies, have been investigated as high reactive sites for photocatalytic CO 2 reduction. These studies have shown that vacancies can improve performance of photocatalysts in at least three ways: 1) they can change the surrounding electron density, this benefits the affinity of CO 2 molecules, 2) introduce a defect energy level in the bandgap that favors light adsorption, and 3) some vacancies can act as photogenerated electrons capture sites to promote charge separation.…”

Highly Ordered and Crystalline Cu Nanowires in Anodic Aluminum Oxide Membranes for Biomedical Applications

“…Based on the morphology‐dependent physical and chemical properties of Cu nanostructures, these have potential applications in water management, i.e., sensing and pollutants removal as evidenced through our earlier findings . These nanostructures are explored for removal of several pollutants from water through adsorption or photocatalytic degradation . The possible recycling of Cu 1+ ions under light on the Cu nanostructures' interface promotes their role as photocatalysts .…”

Bismuth Atom Tailoring of Indium Oxide Surface Frustrated Lewis Pairs Boosts Heterogeneous CO2 Photocatalytic Hydrogenation

“…This situation is tipping the delicate balance of CO 2 in our atmosphere leading to global warming. To this end, the photocatalytic hydrogenation of CO 2 into value-added chemicals and fuels has attracted global attention, touted a promising means of achieving a carbon-neutral economy [1][2][3] . Although materials such as Pd/Nb 2 O 5 4 , Ru/Al 2 O 3 5 , LDH nanosheets 6 and Co-PS@SiO 2 7 have been successfully employed as photocatalysts for CO 2 hydrogenation, a photocatalyst does not currently exist that can meet all the stringent requirements for practical application, including a broad solar response, high conversion e ciency, robust stability and low cost.…”