Three CuO/CeO2 catalyst with different morphologies of ceria, namely nanospheres, nanorods and nanocubes, were synthesized and used to catalyze the water-gas shift (WGS) reaction. The reactivity tests showed that the Cu supported on the ceria nanospheres exhibited both the highest activity and superior stability when compared with the nanocube and nanorod ceria catalysts. Operando X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) methods were used to characterize these catalysts in their working state. High resolution electron microscopy (HRTEM, STEM) was used to look at the local atomic structure and nano-scale morphology. Our results show that the morphology of the ceria support, which can involve different crystal faces and concentrations of defects and imperfections, has a critical impact on the catalytic properties and influences: (1) the dispersion of CuO in the as-synthesized catalyst; (2) the particle size of metallic Cu upon reduction during the WGS reaction, (3) the stability of the metallic Cu upon variations of temperature, and (4) the dissociation of water on the ceria support. The nanosphere ceria catalyst showed an excellent water dissociation capability, the best dispersion of Cu and a strong Cu-Ce interaction, therefore delivering the best performance among the three WGS catalysts. The metallic Cu, which is the active species during the WGS reaction, was more stabilized on the nanospheres than on the nanorods and nanocubes and thus led to a better stability of the nanosphere catalyst than the other two architectures. Each catalyst exhibited a distinctive line-shape in the 800-1600 cm(-1) region of the DRIFTS spectra, pointing to the existence of different types of carbonate or carboxylate species as surface intermediates for the WGS.

The increasing carbon emissions from various fossil fuels have led to the search for efficient and clean energy sources to replace them. Proton exchange membrane fuel cells (PEMFCs) are a promising alternative, but the use of platinum as a catalyst material poses challenges due to its limited resources and low abundance. This study proposes an efficient method for platinum recovery while retaining spent membranes. The membrane and catalyst were separated using isopropanol, and the spent membrane was dissolved in a 50% ethanol solution to prepare the precursor for subsequent membrane regeneration. Hydrochloric acid (HCl) was used as the leaching agent, and the experimental parameters such as HCl concentration, H2O2 concentration, contact time, and operating temperature were optimized to achieve the highest platinum leaching rate. Finally, through isothermal leaching experiments, the leaching mechanism was investigated using the shrinking core model, indicating the involvement of both surface chemical and inner diffusion mechanisms in the platinum leaching process, primarily controlled by the inner diffusion mechanism. Under optimal conditions, the platinum leaching rate was about 90%, and the activation energy of the reaction was calculated to be 6.89 kJ/mol using the Arrhenius equation.

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