Anchoring Fe–Cu bimetallic oxides on MWCNTs for low-temperature H2S removal under high CO2 concentration

Abstract

To advance the utilization of high-concentration CO₂ produced in biogas upgrading, it is essential to remove associated hydrogen sulfide (H₂S). This study presents a series of bimetallic Fe–Cu oxides supported on multi-walled carbon nanotubes (MWCNTs), which were synthesized to efficiently remove H₂S from CO₂-rich gas at low temperatures. The synergy of the bimetallic elements not only forms a multifaceted active phase but also causes new defects on the MWCNTs, creating more H₂S/CO₂ separation sites. The adsorption experiments demonstrate that the deep H₂S removal performance of the adsorbent is unaffected by the CO₂ concentration, achieving a maximum adsorption capacity of 30.11 mg g⁻¹, which exceeds that of commercial desulfurizers and previously reported adsorbents. Additionally, density functional theory calculations were employed to elucidate that the introduction of Cu species increases the gap in the average adsorption energies between H₂S and CO₂. The adsorbent also exhibited stability after 4-cycle regeneration at room temperature, maintaining 62.6% of its initial H₂S capacity. This work underscores the potential of Fe–Cu oxide/MWCNTs adsorbents as a viable, regenerable solution for H₂S removal in CO₂ purification, offering implications for carbon-negative construction.