Promoted Surface-Interface Catalysis over Mn–Cr Incorporated Cu-Based Catalysts for Efficient Hydrogen Production from Methanol Decomposition

Abstract

To solve the safety problems and economic inefficiency of transporting and storing gaseous hydrogen, developing efficient catalytic decomposition of liquid organic hydrogen carriers for in situ hydrogen production is attracting more and more attention. Here, a series of Cr-doped, Mn-promoted Cu-based catalysts for methanol decomposition were fabricated from quaternary Cu–Mn–Cr–Al layered double hydroxides. It was demonstrated that Mn incorporation promoted the reduction and dispersion of copper species and regulated the electronic properties of surface metallic Cu sites, and an appropriate amount of Cr doping facilitated the generation of smaller Cu particles and reduced the surface acidity over catalysts, thereby favoring the construction of generous interfacial Cu + sites in the form of Cu + –O v –Mn and Cu + –O–M structures (O v: oxygen vacancy; M = Mn or Cr). The Cu-based catalyst bearing a Cr:Mn molar ratio of 0.4 achieved a high hydrogen selectivity of 84.3% at complete methanol conversion, along with long-term stability during 80 h of reaction. Through various exhaustive characterization studies, in situ diffuse reflectance infrared Fourier transform spectra of methanol adsorption and desorption, and density functional theory calculations, it was revealed that abundant interfacial Cu + –O v –Mn and Cu + –O–M structures and favorable Cu + –Cu 0 synergistic effects in Cu-based catalysts efficiently promoted a series of dehydrogenation processes of methanol and reaction intermediates, thus boosting hydrogen production. This study provides effective methods for the construction of Cu-based catalysts by engineering surficial and interfacial sites conducive to the efficient hydrogen production through methanol decomposition.

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