Supported copper–copper oxide nanoparticles as active, stable and low-cost catalyst in the methanolysis of ammonia–borane for chemical hydrogen storage

• Cu–Cu2O–CuO/C catalyst was synthesized and characterized, for the first time.
• Cu–Cu2O–CuO/C catalyst was used in AB methanolysis.
• They provide the highest activity among the first-row metal catalysts.

The physical mixture of copper (Cu) copper(I) oxide (Cu2O) and copper(II) oxide (CuO) nanoparticles supported on activated carbon (Cu–Cu2O–CuO/C) were reproducibly prepared by a simple deposition-reduction technique without using any stabilizer in water at room temperature. The characterization of the resulting material by ICP-OES, P-XRD, XPS, DR-UV/vis, BFTEM and HRTEM techniques reveals that the formation of well-dispersed highly crystalline 3.8 ± 1.7 nm nanoparticles on the surface of activated carbon. These carbon supported Cu–Cu2O–CuO nanoparticles were employed as heterogeneous catalyst in the methanolysis of ammonia–borane (NH3BH3), which has been considered as one of the attractive materials for the efficient storage of hydrogen, under mild conditions. We found that only 3.0 mol % Cu–Cu2O–CuO/C catalyst is enough to catalyze the methanolysis of ammonia–borane with high activity (TOF = 24 min−1) and conversion (>99%) at room temperature. More importantly, the exceptional stability of supported Cu–Cu2O–CuO nanoparticles against to sintering and leaching make Cu–Cu2O–CuO/C recyclable catalyst for the methanolysis of ammonia–borane. Cu–Cu2O–CuO/C catalyst retains >76% of its initial activity with 94% of conversion even at 8th recycle in the methanolysis of ammonia–borane at complete conversion. The study reported here also includes the collection of kinetic data for Cu–Cu2O–CuO/C catalyzed methanolysis of ammonia–borane depending on catalyst [Cu], substrate [NH3BH3] concentrations and temperature to determine the rate expression and the activation parameters (Ea, ΔH#, and ΔS#) of the catalytic reaction.

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