Engineering of crystal phase over porous MnO₂ with 3D morphology for highly efficient elimination of H₂S

In the present work, we report a facile oxalate-derived hydrothermal method to fabricate α-, β- and δ-MnO₂ catalysts with hierarchically porous structure and study the phase-dependent behavior for selective oxidation of H₂S over MnO₂ catalysts. It was disclosed that the oxygen vacancy, reducibility and acid property of MnO₂ are essentially determined by the crystalline phase. Systematic experiments demonstrate that δ-MnO₂ is superior in active oxygen species, activation energy and H₂S adsorption capacity among the prepared catalysts. As a consequence, δ-MnO₂ nanosphere with a hierarchically porous structure shows high activity and stability with almost 100% H₂S conversion and sulfur selectivity at 210 °C, better than majority of reported Mn-based materials. Meanwhile, hierarchically porous structure of δ-MnO₂ nanosphere alleviates the generation of by-product SO₂ and sulfate, promoting the adoptability of Mn-based catalysts in industrial applications.