Browsing by Subject "catalysis"

Now showing 1 - 2 of 2

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 Ceramiki
The 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.
Access status: Restricted ,
Smektyty podpierane polikationami tytanowymi jako sorbenty i katalizatory w ochronie środowiska
(Data obrony: 2014-07-25) Urbańczyk, Marcin
Wydział Geologii, Geofizyki i Ochrony Środowiska
Exchanging the interlayer cations with large, oligomeric titanium hydroxycations leads to increase of interlayer distance and open structure of montmorillonite. After calcination, titanium hydroxycations turn into oxide pillars. Pillared interlayer clays (PILCs) are thermally stable microporous structures with large surface area. Pillared montmorillonites exhibit unique sorption and catalytic properties in many industrially important chemical processes. Ti-PILC are very active catalysts for processes which limit the release of toxic pollutants into the atmosphere: combustion of chlorinated volatile organic compounds (CVOCs) and Selective Catalytic Reduction of nitrogen oxides by ammonia or hydrocarbons. Studies have shown that Ti-PILC sorbed a certain amount of carbon dioxide. The strength of CO2 sorption was different, what is shown as 3 peaks on graph of CO2 content. After heating of Ti-PILC (200oC) the strength of sorption increased as evidenced by the three peaks shift towards higher temperatures.