![]() ![]() The catalysts were comprehensively characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy (RS), and X-ray fluorescence spectroscopy. Manganese-cobalt spinels supported on the MWCNTs were synthesized by a microwave-assisted solvothermal route. Commercial MWCNTs were oxidized by boiling in concentrated nitric acid and then double-doped with N and S heteroatoms using thiourea precursor. Multi-walled carbon nanotubes (MWCNTs) doped with nitrogen and sulfur atoms and with deposited manganese–cobalt spinel catalysts were studied to reveal the role of active centers in the oxygen reduction and evolution reactions (ORR and OER) in alkaline media. In principle, the efficiency of the HER/HOR could be improved by diminishing the density of the strong adsorption sites and/or increasing that of the weak adsorption sites. The surface area calculated from the voltammetric charges of HER/HOR yields the electrode’s total surface area with overestimated values of about 30% compared with EASA. HER occurs only on the w-sites, whose equivalent surface area makes up the electrochemical active surface area (EASA), while that corresponding to the s-sites is inactive. The fine structure is determined by the hydrogen evolution reaction (HER/adsorption) and the hydrogen oxidation reaction (HOR/desorption) that take place on different virtual groups of the randomly distributed adsorption sites, the strong(s)– and weak(w)–adsorption sites. The deconvolution was carried out with the asymmetric double sigmoid function adapted to voltammetric applications and a general-purpose peak fitting program. CVs were recorded in 1M HClO4 solution, at T = 298 K, for three different values of the minimum scanning potential near the electrode equilibrium potential. The cyclic voltammograms (CVs) in the H–region of Pt–black electrodes were deconvoluted to reveal and analyses their peaks components (the fine structure). ElecKeywords: Pt-black, H-region, cyclic voltammograms, asymmetric double sigmoid function, deconvolution, HER/HOR. The surface area calculated from the voltammetric charges of HER/HOR yields the electrode's total surface area with overestimated values of about 30% compared with EASA. The fine structure is determined by the hydrogen evolution reaction (HER/adsorption) and the hydrogen oxidation reaction(HOR/desorption) that take place on different virtual groups of the randomly distributed adsorption sites, the strong(s)-and weak(w)-adsorption sites. The cyclic voltammograms (CVs) in the H-region of Pt-black electrodes were deconvoluted to reveal and analyze their peak components (the fine structure). In particular, it enables Pawley refinement of powder diffraction data and size–strain analysis. ![]() It specializes in fitting a sum of bell-shaped functions to experimental data. Fityk is portable, open-source software for nonlinear curve fitting and data analysis. The journal is the primary place where crystallographic computer program information is published. Developments of instrumentation and crystallo-graphic apparatus, theory and interpretation, numerical analysis and other related sub-jects are also covered. Articles published in the Journal of Applied Crys-tallography focus on these methods and their use in identifying structural and diffusion-controlled phase transformations, structure–property relationships, structural changes of defects, interfaces and surfaces, etc. For further information see Many research topics in condensed matter research, materials science and the life sci-ences make use of crystallographic methods to study crystalline and non-crystalline mat-ter with neutrons, X-rays and electrons. Republication of this article or its storage in electronic databases other than as specified above is not permitted without prior permission in writing from the IUCr. Author(s) of this paper may load this reprint on their own web site or institutional repository provided that this cover page is retained. ![]()
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