Khalid Mahmoud Hassan

Simultaneous and selective electrochemical determination of hydroquinone, catechol and resorcinol at poly(1,5-diaminonaphthalene)/glassy carbon-modified electrode in different media

The electrochemical behavior of phenolic isomers hydroquinone (HQ), catechol (CC) and resorcinol (RC) was examined in poly(1,5-diaminonaphthalene)/glassy carbon-modified electrode (P1,5-DAN/GC M.E.) by cyclic voltammetry (CV), square wave voltammetry (SWV) and chronoamperometry (CA) techniques in perchloric acid (HClO4) and phosphate buffer solution (PBS, pH 7.0). P1,5-DAN/GC M.E. was investigated for simultaneous determination of HQ, CC and RC in single, binary and ternary systems. Oxidation peak potentials were negatively shifted with increasing oxidation peak current for HQ, CC and RC at P1,5-DAN/GC M.E. compared with bare GC electrode. The obtained results illustrate that the former electrode exhibits better performance towards the three isomers in PBS rather than in HClO4 solution. The catalytic currents for different concentrations of HQ, CC and RC showed good relationship in the range of 0.1–100 μM for all analytes and low detection limits (LOD) of 0.034, 0.059 and 0.14 μM for them, respectively, in a ternary system in PBS at pH 7.0. This method has been practically applied for the detection of these isomers in tap water with acceptable results.

Electrocatalytic oxidation of ethanol at Pd, Pt, Pd/Pt and Pt/Pd nano particles supported on poly 1,8-diaminonaphthalene film in alkaline medium

An ethanol oxidation reaction (EOR) in alkaline medium was carried out at palladium (Pd) or platinum (Pt) nanoparticles/poly 1,8-diaminonaphthalene (p1,8-DAN) composite catalyst electrodes. Pd and Pt were incorporated onto a p1,8-DAN/GC electrode by a cyclic voltammetry (CV) strategy. The obtained Pd/p1,8-DAN/GC, Pt/p1,8-DAN/GC, Pt/Pd/p1,8-DAN/GC and Pd/Pt/p1,8-DAN/GC modified electrodes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and cyclic voltammetry (CV) techniques. Electrode surface areas (ESAs) of the obtained catalysts were calculated by carbon monoxide (CO) adsorption using differential electrochemical mass spectroscopy (DEMS). The electrocatalytic oxidation of ethanol (EtOH) at the catalyst electrodes was considered in 0.5 M NaOH solutions by CV and chronoamperometric techniques. The catalyst electrodes significantly enhanced the catalytic efficiency for EOR compared to a bare glassy carbon (GC) electrode. Bimetallic catalyst electrodes demonstrate improved catalytic activity, superior durability and higher tolerance to (CO) poison generated in the development of EOR compared with Pd/p1,8-DAN and Pt/p1,8-DAN catalysts, giving priority to Pt/Pd/p1,8-DAN/GC electrodes. Viability parameters, such as NaOH and EtOH concentrations, scan rate and upper potential limits, were examined and analyzed. This study suggests that the prepared catalysts have pronounced potential applications in direct EOR in fuel cells.