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

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.