Mikuła, Andrzej
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nauki chemiczne
inżynieria materiałowa
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Item type:Article, Access status: Open Access , Transition metal sulfides for electrochemical applications: Controlled chemical conversion of CuS to Ag2S(2022) Mazurków, Julia; Kusior, Anna; Mikuła, Andrzej; Radecka, Marta
Wydział Inżynierii Materiałowej i CeramikiTransition metal sulfides have received great attention as electrocatalysts for electrochemical sensors and water electrolysis. In the present study, a facile and rapid chemical conversion route was used for the synthesis of partially and fully converted $Ag_{2}S$ from tube-like CuS. The morphology of the obtained materials was investigated by scanning electron microscopy (SEM) and transition electron microscopy (TEM), revealing that the complex shape of CuS was maintained after the conversion. Information about phase and elemental composition was obtained by X-ray diffraction (XRD), Raman spectroscopy, X-ray fluorescence spectrometry (XRF), and inductively coupled plasma optical emission spectrometry (ICP-OES). The surface composition was analyzed utilizing X-ray photoelectron spectroscopy (XPS). The results indicated that it was possible to precisely control the contribution of each sulfide by varying precursors ratio. Moreover, the conducted experiments enabled to schematically illustrate the $CuS-Ag_{2}S$ junction and propose a conversion mechanism. The electrochemical behavior of the materials was examined using cyclic voltammetry (CV) in the potential range of biomolecules electrooxidation as well as water splitting. Special attention was devoted to reactions occurring on $Ag_{2}S$-modified electrodes in alkaline and neutral media. It was found that the formation of subsequent oxides, their reduction, and the recovery of $Ag_{2}S$ are diffusion-controlled processes.Item type:Article, Access status: Open Access , Predicting sensitivity to glucose in metal sulfides: a structural and surface characterization study(2024) Mazurków, Julia; Kusior, Anna; Mikuła, Andrzej; Radecka, Marta
Wydział Inżynierii Materiałowej i CeramikiThe increasing prevalence of diabetes is leveraging the development of improved management technologies, including non-enzymatic glucose sensors that offer enhanced stability and longer operation times. However, the lack of reliable methods to predict materials' electrocatalytic activity remains a significant barrier to their advancement. Herein, we obtained transition metal sulfides ($CuS$, $Ag_{2}S$, $FeS_{2}$, and $α-NiS$) with similar shapes and sizes using wet chemical methods. Detailed structural and surface characterization revealed the presence of metals in mixed oxidation states and the formation of disulfides and polysulfides on the surface of air-exposed materials. The optical measurements supported by theoretical calculations indicated band gaps of 1.74, 0.98, and 1.14 eV in $CuS$, $FeS_{2}$, and $Ag_{2}S$, respectively. Nickel sulfide exhibited an intraband transition at 1.42 eV. The electrocatalytic activity toward glucose was investigated using cyclic voltammetry and chronamperometry. The lowest oxidation potential of 615 mV showed $α-NiS$, whereas the highest – $Ag_{2}S$ (860 mV). The sensitivity determined in chronoamperometry measurements increased in the order of $α-NiS>CuS>Ag_{2}S>FeS_{2}$. Furthermore, selectivity studies revealed that $FeS_{2}$ responded only to strong reductants, while $α-NiS$ to all examined electroactive species. In the last step, a clear relationship was identified between the d-band center position $(d_{bc})$ in metal sulfides and their electrochemical performance. The dbc relative to the Fermi level is optimal in $CuS$ and $NiS$ (around −2 eV) for forming bonds with glucose and intermediates, while in $Ag_{2}S$ and $FeS_{2}$, it lays too far or too close for effective electrooxidation.