Theoretical investigation on the role of external oxygen facilitating oxidative dehydrogenation of hydrogen sulfide on Fe-based oxide catalysts

Abstract

The oxidative dehydrogenation (ODH) of hydrogen sulfide (H2S) is a critical process in biogas purification, enabling cleaner and more efficient utilization of renewable energy sources. This study employs density functional theory (DFT) and microkinetic modeling to investigate the role of external oxygen (Oext) in enhancing the catalytic performance of O2/α-Fe2O3(0 0 0 1) surfaces. The findings reveal that Oext significantly lowers the activation energy of key reaction steps, promotes more favorable reaction pathways, and mitigates sulfur poisoning by stabilizing lattice oxygen and suppressing the formation of oxygen vacancies. The unique electronic and structural properties of the O2/α-Fe2O3(0 0 0 1) surface facilitate improved catalyst activity and extended operational stability, addressing key challenges in sustainable energy technologies. The existence of the Oext can decrease the optimal temperature of ODH of H2S from >1150 K on the pristine α-Fe2O3(0 0 0 1) surface to 850 K on the O2/α-Fe2O3(0 0 0 1) surface. Furthermore, undergoing the ODH reaction to the steady state is 1.25 × 103 times faster than that of a lean α-Fe2O3(0 0 0 1) surface. Also, the amount of poisoned species of S* on the O2/α-Fe2O3(0 0 0 1) surface is lowered significantly. This work advances the design of robust catalysts for efficient H2S removal by providing a deeper understanding of catalytic behavior and deactivation mechanisms. The insights presented here contribute to cleaner energy production and environmental protection, bridging fundamental knowledge and practical applications in catalysis.