Browsing by Author "Szunerits S."

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Cathodic activation of titanium-supported gold nanoparticles: An efficient and stable electrocatalyst for the hydrogen evolution reaction
(2016-04-27) Amin M.A.; Fadlallah S.A.; Alosaimi G.S.; Kandemirli F.; Saracoglu M.; Szunerits S.; Boukherroub R.
As-polished titanium (Ti) substrates decorated with dispersed gold nanoparticles (Au NPs/Ti) of various sizes and densities were prepared here to effectively catalyze hydrogen evolution reaction (HER) in 0.5 M H2SO4. These materials were synthesized adopting a facile one-step wet chemical method without using reducing agents, stabilizers, or any chemical pre-treatment, where Ti acts as both the reducing agent and support. This was achieved via soaking the Ti substrates for 30 min in a gold precursor bath as a function of temperature (5-65°C). Morphological characterizations of the synthesized Au NPs/Ti catalysts indicated a size decrease and density increase of loaded Au NPs with the rise of temperature. Cathodic polarization measurements revealed that the catalyst loaded with the highest density of Au NPs exhibited the best HER activity with onset potential (EHER), exchange current density (jo), and Tafel slope (βc) of -44 mV (RHE), 6.0 × 10-3 mA cm-2, and 40 mV decade-1, respectively. This activity has markedly increased upon cathodic activation (cathodic pre-polarization treatment at -2 V (SCE) for 12 h) that yielded a Ti substrate with a porous-like network structure decorated with highly dispersed Au NPs. In addition, a catalytically active TiH2 phase was formed (as evidenced from XRD and XPS) on such a porous substrate. Such cathodically pre-treated catalyst recorded HER electrochemical parameters of -18 mV (RHE), 0.117 mA cm-2, and 38 mV decade-1, thus approaching the commercial Pt/C catalyst (EHER: 0.0 mV, jo: 0.78 mA cm-2, and βc: 31 mV dec-1). The stability of the best catalyst was assessed employing cyclic polarization and chronoamperometry measurements. It exhibited a good stability with improved activity during stability testing.
Electrochemical, theoretical and surface physicochemical studies of the alkaline copper corrosion inhibition by newly synthesized molecular complexes of benzenediamine and tetraamine with π acceptor
(2020-12-15) Ibrahim M.M.; Mersal G.A.M.; Fallatah A.M.; Saracoglu M.; Kandemirli F.; Alharthi S.; Szunerits S.; Boukherroub R.; Ryl J.; Amin M.A.
Two charge transfer complexes, namely [(BDAH)+(PA−)] CT1 [(BTAH)2+(PA−)2] and CT2 (BDAH = 1,2-benzenediamine, BTAH = 1,2,4,5-benzenetetramine, and PA− = 2,4,6-trinitrophenolate), were synthesized and fully characterized using various spectroscopic techniques. CT1 and CT2 were tested as inhibitors to effectively control the uniform and anodic corrosion processes of copper in an alkaline electrolyte (1.0 M KOH) using various electrochemical techniques. As a reference point, results were compared with the potassium salt of the π-acceptor potassium 2,4,6-trinitrophenolate (designated here as PA−K+). The highest inhibition efficiency (97%) was recorded for inhibitor CT2 at a concentration of 1.0 mM. The inhibition mechanism was discussed based on scanning electron microscopy and X-ray photoelectron spectroscopy results of the corroded and inhibited Cu surfaces. A theoretical study, based on quantum-chemical calculations of the synthesized compounds, performed by the DFT/B3LYP method with a 6-311++G(2d,2p) basis set by using Gaussian 09, Revision A.02 program, was also included to support experimental findings. The various quantum chemical parameters such as EHOMO, ELUMO, chemical hardness, and chemical softness of the investigated molecules were calculated, and their correlation with the inhibition efficiency of the synthesized compounds was discussed.