Ceria-trapped single-atom rhodium catalysts for efficient ethanol steam reforming to hydrogen†

Abstract

Ethanol steam reforming (ESR) is a promising technique for sustainable hydrogen production, achieving high hydrogen yields. Herein, we prepare a series of Rh–Ce/Al₂O₃ catalysts with enhanced catalytic performance by modulating the interaction between active Rh and the CeO₂ promoter. Various characterization techniques, including HAADF-STEM and XAFS, demonstrated that new Rh–O–Ce sites were formed by the effective trapping of single-atom Rh species by CeO₂ nanoparticles on the Rh–Ce₅/Al₂O₃ catalyst. In situ DRIFTS-MS combined with isotopic kinetic analysis further revealed that Rh–O–Ce sites significantly enhanced water activation, which promoted the production of acetate, a reactive intermediate in ESR. Acetate was dehydrogenated to CO, which subsequently reacted with H₂O to form formate in the water–gas shift (WGS) reaction, a critical step in ESR. Similarly, the enhanced water activation also promoted the formation of formate, which ultimately decomposed to H₂ and CO₂. Consequently, the Rh–Ce₅/Al₂O₃ catalyst exhibited an excellent hydrogen production rate of 22.4 mmol g⁻¹ min⁻¹ at 450 °C and remarkable stability in the ESR reaction. The findings revealed the role of Rh–O–Ce sites in enhancing the performance of Rh-based catalysts in ESR, beneficial for the design of efficient ESR catalysts.