Highly Efficient Porous Fe_xCe_1–xO_2−δ with Three-Dimensional Hierarchical Nanoflower Morphology for H₂S-Selective Oxidation

Abstract

CeO2-based catalysts are potentially suitable for H2S-selective oxidation, but their practical application is limited due to the problem of sulfate formation. Herein, we report a facile citric acid-assisted hydrothermal process for the fabrication of porous Fe-doped CeO2 with flower-like morphology that can drastically promote the catalytic activities of CeO2 with high durability. Among the synthesized catalysts, the one with well-defined (110) and (100) planes is highly active for H2S-selective oxidation with H2S conversion and sulfur selectivity of almost 100% at 220 °C, superior to most of the reported Ce-based catalysts. Meanwhile, outstanding catalytic stability is achieved because the presence of Fe ions alleviates ceria deactivation due to sulfation. The results of systematic investigation prove that the doping of Fe not only raises the density of oxygen vacancies but also promotes the redox ability and oxygen activity of the catalyst. We conducted in situ DRIFTS (diffuse reflection infrared Fourier transform spectroscopy) experiments and density functional theory (DFT) calculations to disclose the reaction mechanism of H2S oxidation. The derived insights are important for the design of efficient ceria-related catalysts for practical applications.

Solvothermal Synthesis Routes to Substituted Cerium Dioxide Materials

“…Their method involved using nitrates in ethylene glycol, heated to 180 °C for 28 h. They followed this up by heating the sample to 450 °C for 4 h. The resulting materials all matched the XRD pattern associated with CeO2, rather than Fe2O3. Zheng et al also produced Fe-doped ceria, forming the materials in a "nanoflower" morphology, Figure 7 [73]. This required mixing nitrates in urea, citric acid and ammonia, heating to 155 °C for 26 h and then firing to 500 °C for a further 3 h. The materials synthesised had an iron content of between 4 and 12 mol% and were applied for the selective oxidation of H2S.…”

Electronic State Modulation and Reaction Pathway Regulation on Necklace‐Like MnOx‐CeO2@Polypyrrole Hierarchical Cathode for Advanced and Flexible Li–CO2 Batteries

“…These phenomena probably due to Mn ions with a smaller radius (Mn 2+ 0.080 nm, Mn 3+ 0.066 nm, and Mn 4+ 0.054 nm) replaced the cerium ions with a larger radius (Ce 4+ 0.094 nm) and formed a MnO x ‐CeO 2 solid solution as previously reported. [ 17,39,40 ] This point is supported by Raman spectroscopy furtherly. As shown in Figure 2c, the Raman peak located at 460 cm –1 was linked to F 2g mode of fluorite‐type CeO 2 , while the peak located at 645 cm –1 was attributed to MnO bond in MnO x .…”

“…Meanwhile, reasonable microscopic morphology design is believed to be beneficial for the full exposure of reactive sites. [ 17,18 ] As a non‐noble metal with rich valence and high stability, manganese (Mn) is expected to form a bimetallic solid solution with CeO 2 , thereby realizing the reformation of the electronic structure of a single‐metal catalyst and generating the flexible redox shift between Mn/Ce oxides (Mn 3+ + Ce 4+ ↔ Mn 4+ + Ce 3+ ). [ 19 ] In the electrochemical reaction process, this well‐defined composite catalyst can achieve optimized active site exposure, which enhances the adsorption of reactants and the destruction of chemical bonds, thereby reducing the reaction energy barrier and improving reaction activity.…”

Highly Active and Sulfur‐Resistant Fe–N4 Sites in Porous Carbon Nitride for the Oxidation of H2S into Elemental Sulfur

“…[4][5][6][7] Among them, the selective oxidation of H 2 S into S is considered the most viable as the process is cost competitive and without thermodynamics limitation. [8][9][10] Among the developed catalysts for the oxidation of H 2 S into elemental S, those based on iron (e.g., Fe 2 O 3 , Fe included bimetals and composites) are of particular interest owing to…”

“…[ 4–7 ] Among them, the selective oxidation of H 2 S into S is considered the most viable as the process is cost competitive and without thermodynamics limitation. [ 8–10 ]…”