Oxygen Vacancy Drives CoO Atomic Layers Directional Photoreduction of CO₂ to CH₄

Abstract

Plagued by the dual challenges of energy scarcity and environmental pollution, photocatalytic CO2 reduction has emerged as a vital engineering for collecting solar energy to convert CO2 into renewable fuels. Herein, the ultrathin CoO atomic layers with varying concentrations of oxygen vacancies are designed to photoreduce CO2 and explore the mechanism of oxygen vacancy for CO2 photoreduction. Density functional theory calculations illustrate that the oxygen vacancy not only enhances the available photoelectrons efficiency of CoO structures by improving the absorption of solar light and promoting the surface separation of electron–hole pairs, but decreases the highest occupied molecular orbital of CO2 and the potential barrier of *CO conversion to *CHO, driving the CO2 directed photoreduction toward CH4. Finally, the rich‐oxygen vacancies CoO atomic layers significantly enhance the effective photoelectrons efficiency with 136.3 μmol g−1 h−1 compared to 44.6 μmol g−1 h−1 for 2D‐CoO atomic layers. Moreover, the CH4 selectivity also rises from 39.4% to 72.4% through the regulation of oxygen vacancies. This work promotes the development of Co‐based semiconductors for CO2 photocatalytic reduction, and elucidates the mechanism of oxygen vacancy for CO2 photoreduction, which provides valuable insights for the design and optimization of similar photocatalysts in both experimental and theoretical domains.

Intrinsic bimetallic cations regulating band centers and reactive sites for boosting CO2 photoreduction

“…Since the conduction band (CB) of n-type semiconductors is generally 0.1–0.3 V lower than the E fb value, 40 the CB positions of BOB, CBOB-c1, and CBOB-c2 are estimated to be located at −1.35, −1.36, and −1.19 V, respectively. Furthermore, the valence band (VB) can be identified at 1.38, 1.37, and 1.53 V according to the formula (1): 41 E g = E CB − E VB …”

Comprehensive Insight into Construction of Active Sites toward Steering Photocatalytic CO2 Conversion

“…Theoretical calculations illustrate that the Vo improves the absorption of solar light, promotes the surface separation of electron‐hole pairs, and decreases the potential barrier of *CO conversion to *CHO, thus directing the CO 2 photoreduction toward CH 4 . [ 33 ] The integration of Ni−Co dual sites on Ni‐doped Co 3 O 4 ultrathin nanosheets assembled double‐hollow nanotube was fabricated through a successive in situ phase transformation strategy, which basically involves hydrothermal reaction and pyrolysis processes. Quasi in situ spectra and DFT calculations demonstrate that the declining of d‐band center of Ni−Co dual sites enables for the electron's accumulation in the d xz /d yz ‐2π* and d z2 ‐5σ orbitals.…”