A Hierarchical Z‑Scheme α‐Fe₂O₃/g‐C₃N₄ Hybrid for Enhanced Photocatalytic CO₂ Reduction

Abstract

The challenge in the artificial photosynthesis of fossil resources from CO by utilizing solar energy is to achieve stable photocatalysts with effective CO adsorption capacity and high charge-separation efficiency. A hierarchical direct Z-scheme system consisting of urchin-like hematite and carbon nitride provides an enhanced photocatalytic activity of reduction of CO to CO, yielding a CO evolution rate of 27.2 µmol g h without cocatalyst and sacrifice reagent, which is >2.2 times higher than that produced by g-C N alone (10.3 µmol g h ). The enhanced photocatalytic activity of the Z-scheme hybrid material can be ascribed to its unique characteristics to accelerate the reduction process, including: (i) 3D hierarchical structure of urchin-like hematite and preferable basic sites which promotes the CO adsorption, and (ii) the unique Z-scheme feature efficiently promotes the separation of the electron-hole pairs and enhances the reducibility of electrons in the conduction band of the g-C N . The origin of such an obvious advantage of the hierarchical Z-scheme is not only explained based on the experimental data but also investigated by modeling CO adsorption and CO adsorption on the three different atomic-scale surfaces via density functional theory calculation. The study creates new opportunities for hierarchical hematite and other metal-oxide-based Z-scheme system for solar fuel generation.

LaCoO3 acts as a high‐efficiency co‐catalyst for enhancing visible‐light‐driven tetracycline degradation of BiOI

“…Interestingly, as compared with the bare BiOI, the absorption peak derived from the vibration of the Bi–O bond in the LaCoO 3 /BiOI hybrids gradually shifted to higher wavenumbers with increasing content of LaCoO 3 , which could be ascribed to the decrease in electron concentration of BiOI owing to the strong interfacial interactions between closely contacted phases of BiOI and LaCoO 3 , coinciding with the XPS results as described above. A similar phenomenon was reported by others …”

In Situ Fabrication of 3D Octahedral g‐C3N4/BiFeWOx Double‐Heterojunction for Highly Selective CO2 Photoreduction to CO Under Visible Light

“…EPR analysis, using DMPO as a spin trapping reagent in methanol or H 2 O, was carried out to investigate the radicals more intuitively . As shown in Figure a, the EPR signals of DMPO‐⋅OH adduct could be observed obviously in the GN‐5 %/BFW photocatalytic system, however, there was a much weaker signal for BFW, and for g‐C 3 N 4 , no signals can be detected, which clearly implied the GN‐5 %/BFW composite generated more ⋅OH radicals than the individual catalyst . Meanwhile, a similar consequence was obtained in the DMPO‐O 2 analysis.…”

“…However, the photocatalytic activity of single phase g‐C 3 N 4 is limited by the fast recombination of photoinduced electrons (e − ) and holes (h + ) . Considerable efforts have been devoted to promoting the photocatalytic efficiency, such as structure engineering, doping and constructing heterojunction, etc. Among these methods, constructing g‐C 3 N 4 ‐based composites has been considered as a simple and efficient method to suppress the recombination of photogenerated carriers and extend the sunlight response regions…”

α−Fe2O3 Nanoparticles/Porous g−C3N4 Hybrids Synthesized by Calcinations of Fe‐based MOF/Melamine Mixtures for Boosting Visible‐Light Photocatalytic Tetracycline Degradation

“…Nevertheless, the short lifetime of photo‐generated charge carriers and small hole diffusion length greatly hinder the widespread application of α−Fe 2 O 3 in photocatalysis . In the past several years, the coupling of g−C 3 N 4 with α−Fe 2 O 3 has been an effective route to enhance themselves′ visible‐light photocatalytic activity in various fields such as pollutant degradation, hydrogen production, CO 2 reduction, organic synthesis, and nitrogen fixation . Due to the appropriate band positions of α−Fe 2 O 3 and g−C 3 N 4 , the strong interfacial coupling of α−Fe 2 O 3 /g−C 3 N 4 hybrids largely promoted the transfer and separation of photoinduced charge carriers by common or even Z‐scheme modes, directly accounting for their high photocatalytic efficiency.…”