Formation, Detection, and Function of Oxygen Vacancy in Metal Oxides for Solar Energy Conversion

Abstract

for green hydrogen production, carbon dioxide reduction, and nitrogen fixation via photocatalytic process etc. [6][7][8][9][10] Intrinsic MOs normally possess weak conductivity due to their relatively large bandgap, which severely limit their application. In order to make MOs good candidates for renewable energy conversion, many strategies have been developed, including facet engineering, [11] cocatalyst loading, [12] nanostructure engineering, and defect engineering. [13] Among them, defect engineering, such as doping strategy, [14] creating oxygen vacancies, [15] lattice distortion, [16] is regarded as one of the most effective pathways, thus has been widely applied in designing efficient photocatalysts. As one of the most common defects, oxygen vacancy (V O ) can be created along with the oxide photocatalysts preparation process, leading to drastically changed properties in the MOs. For instance, the generation of V O in the bulk of a MO photo catalyst can easily lead to the changes of charge separation and transfer process. [18] Meanwhile, the V O created on the surface of photocatalysts can monitor the surface charge injection process. [19] Therefore, V O has been intentionally introduced to a variety of MOs for effective photocatalysts design.As a typical Shockley defect, V O has been studied for over one century. Many significant understandings about the structure and functions of V O have been achieved. Especially in the field of catalysis, V O can play a determining role in tailoring the catalytic capacity. For example, MgO is inert to carbon monoxide (CO) on defect-free (100) facet, but can easily achieve low temperature CO oxidation in the presence of V O . [21,22] Some review papers have summarized the characterization and functions of V O . [22][23][24] But the understanding of the structure-function relationship of V O is still not comprehensive. Especially in the field of photocatalysis research, due to the dynamic features of V O and the surrounding environment, there are still many debates about the V O in terms of its detection and roles during the catalytic process, but little discussion has been presented in previous reviews. For instance, the V O characterized by X-ray photoelectron spectroscopy (XPS) has sparked heated debates because of various explanations of the XPS peaks. [18][19][20][21][22][23][24][25] In terms of the role of V O , some studies have shown the V O promoted charge recombination via photoluminscence, [26,27] while many others have indicated that it benefits solar energy conversion. [28] Herein we provide a critical review focusing on these open questions in terms of the formation, detection, and function of

Oxide coatings with immobilized Ce-ZSM5 as visible light photocatalysts

“…It is also well known that oxygen vacancy defects play an important role in photoactivity of metal oxide photocatalysts. 22,23 XRD data (Fig. 1) shows that prolonged PEO processing time results in the formation of aluminosilicate phase that possesses high density of oxygen vacancies, which is also confirmed by PL measurements (Fig.…”

Excited Electron‐Rich Bi(3–x)+ Sites: A Quantum Well‐Like Structure for Highly Promoted Selective Photocatalytic CO2 Reduction Performance

“…[ 22 ] To determine the surface defects type, low‐temperature electron paramagnetic resonance (EPR) is employed to obtain fingerprint information for the trapped electrons and surface defects. [ 23 ] As shown the Figure 1h, the EPR signal at g = 2.001 is assigned to electrons trapped on oxygen defects. [ 24 ] The bulk PBOC prepared by traditional calcination shows small signals and DUC PBOC prepared by the solvothermal method displays enhanced EPR signals.…”

Structural Regulation of Oxygen Vacancy‐Rich K0.5Mn2O4Cathode by Carbon Hybridization for Enhanced Zinc‐Ion Energy Storage

“…For metal oxides, specific external environments such as high temperature with an inert atmosphere or chemical reduction conditions will cause oxygen separation in the lattice, leading to oxygen loss and the formation of oxygen vacancies. [29] The electronegativity of K and Mn in the oxide is less than that of O. Therefore, the loss of oxygen is analogous to taking replacing one oxygen atom with two positively charged electron holes.…”