Construction of α- and γ- mixed phase Fe2O3 enhances the release of lattice oxygen thus achieving selective catalytic oxidation of H2S at low temperature

Increasing the oxygen vacancy (Ov) content and inducing lattice oxygen activation are critical for enhancing the oxidation performance of transition metal oxides. However, precisely regulating these properties remains a significant challenge. In this study, a stepwise pyrolysis method was employed on a colloidal complex formed by citric acid coordinated with Fe(NO 3 ) 3 ·9H 2 O to synthesize Fe 2 O 3 -X catalysts comprising a mixture of α- and γ-Fe 2 O 3 characterized by abundant surface oxygen vacancies and activated lattice oxygen. The resulting Fe 2 O 3 -1 presented excellent low-temperature H 2 S selective catalytic oxidation (H 2 S-SCO) performance, achieving selective oxidation of H 2 S at 130°C with removal efficiency and sulfur selectivity exceeding 95 % and 85 %, respectively, within 60 h. Characterization results show that the γ-Fe 2 O 3 induced by citric acid forms a crystal interface with the α-Fe 2 O 3 . At the interface, the asymmetrically coordinated lattice oxygen is more likely to be released from the catalyst, thereby enhancing the oxidation ability of the catalyst. Furthermore, the synthesis method effectively modulates the catalyst’s surface basicity, resulting in an optimal distribution of basic sites that mitigates catalyst poisoning and deactivation. This study presents a straightforward approach for synthesizing Fe 2 O 3 catalysts with enhanced oxidation ability, offering valuable insights for developing more efficient transition metal catalysts.