Plasma-enhanced comparative hydrothermal and coprecipitation preparation of CuO/ZnO/Al₂O₃ nanocatalyst used in hydrogen production via methanol steam reforming

Graphical abstract: CuO/ZnO/Al₂O₃ nanocatalyst is synthesized by hydrothermal and coprecipitation methods. In order to evaluation the effects of plasma treatment, synthesized samples by each preparation method are exposed under non-thermal glow discharge plasma. It is obvious from FESEM images that plasma treatment can significantly affect surficial morphology and particles size distribution of the nanocatalysts. The most uniform distribution of isomorph particles and the smallest size of particles in the sample which is synthesized by plasma assisted coprecipitation method can facilitate achieving of reactants to surficial active phases and this leads to the best performance of this sample in steam reforming of methanol reaction. - Highlights: • Hydrothermal vs. coprecipitation synthesis of CuO/ZnO/Al₂O₃ nanocatalyst. • Improvement of catalytic properties by applying non-thermal glow discharge plasma. • Better performance of plasma-coprecipitated nanocatalyst vs. plasma-hydrothermal one. • Enhanced hydrogen production over plasma treated nanocatalysts. - Abstract: The CuO/ZnO/Al₂O₃ nanocatalyst was synthesized using hydrothermal and coprecipitation methods. Then they were exposed to glow discharge plasma for 45 min at 1000 V. The performance of prepared nanocatalysts in conversion of methanol to hydrogen was investigated in steam reforming of methanol reaction. Various characterization techniques such as X-ray diffraction, field emission electron microscopy, particle size distribution, EDX-dot mapping, BET surface area and Fourier transform infrared spectroscopy were used in order to obtain physicochemical properties of synthesized nanocatalysts. XRD diffraction patterns showed that applying coprecipitation method and also glow discharge plasma, led to more dispersion of CuO (1 1 1) crystallite plate. FESEM images displayed that using non-thermal plasma assisted coprecipitation synthesis method caused to best surficial morphology and particle size distribution in CuO/ZnO/Al₂O₃ sample. EDX-dot mapping analysis demonstrated that the CuO/ZnO/Al₂O₃ sample had the most uniform dispersion of elements. Evaluation of catalytic performance indicated that plasma assisted coprecipitation synthesized CuO/ZnO/Al₂O₃ sample had the highest conversion of methanol and the lowest CO generation among other samples in the reaction. Stability assessment of the performance of CuO/ZnO/Al₂O₃ nanocatalyst represented that conversion of methanol and products selectivity were approximately constant through long term use in steam reforming of methanol reaction.