The Cu–Al2O3 interface: an unignorable active site for methanol steam reforming hydrogen production

Abstract

Methanol steam reforming (MSR) is a convenient method for in situ hydrogen production and broadens hydrogen energy application. Identifying the intrinsic activity of Cu-based catalysts for MSR and developing more efficient catalysts is a significant topic for applying in situ hydrogen production. Here, we developed a series of copper catalysts supported by Al₂O₃ with varying copper contents. The highest hydrogen production rate of 147.6 μmol g⁻¹ s⁻¹ was obtained over 10Cu/Al₂O₃ at 250 °C, exceeding most copper-based metallic oxide catalysts. Quasi in situ XPS and CO DRIFTS revealed the variation trend of copper's electronic state in mCu/Al₂O₃ catalysts, where m is the copper loading (in weight percentage). Meanwhile, intermediate formate species adsorbed on the interfacial site at 1602 cm⁻¹ were detected by in situ DRIFTS. This formate species (HCOO–CuAl) dissociated faster to CO₂ and H₂ than those adsorbed on Al₂O₃ (HCOO–Al). The inverse Al₂O₃/Cu catalyst further confirmed that the Cu–Al₂O₃ interfaces play a crucial role in MSR. This work defines the copper–oxide interface as the main active site in MSR and guides the construction of high-performance catalysts.