Combined Effect of Oxygen Vacancies and Mesopore Sizes in ZnO/SiO₂ Adsorbents on Boosting the H₂S Removal Efficiency in Moist Conditions

Abstract While both pore sizes and oxygen vacancies benefit desulfurization on ZnO, their specific roles and the combined effect on the efficiency of this process are still unclear. To address this, ZnO‐based adsorbents with tunable mesopore sizes and concentrations of oxygen vacancies are synthesized. These two features are directly regulated through varying the carbon chain length of dihydric alcohol, which is used as a precursor in the synthesis process. They influenced the desulfurization performance through affecting the diffusion and dissociation of H₂S. The sizes of mesopores determined the amounts of adsorbed water/ thickness of a water film while the amount of oxygen vacancies controlled the contents of hydroxyl groups. The latter not only are replaced by (bi)sulfide anions but also promote the dissociation of H₂S through acid‐base interaction. Adsorbed water contributed to hydroxylation of the surface until the cease of desulfurization. However, too much‐adsorbed water increased the resistance of H₂S diffusion through the water film to the surface of ZnO, deteriorating the performance. The optimal amounts of adsorbed water/thickness of water film and a sufficient amount of oxygen vacancies/hydroxyl groups are provided in the adsorbent with a mesopore size of ∼10 nm leading to a maximum H₂S removal capacity of 151.9 mg g⁻¹.