R.M. Abdel Hameed

Amperometric glucose sensor based on nickel nanoparticles/carbon Vulcan XC-72R

A stable non-enzymatic glucose sensor was constructed by chemical deposition of nickel nanoparticles on carbon Vulcan XC-72R using microwave irradiation technique. The mode and time of microwave irradiation during nickel salt reduction were varied. This was found to affect the morphology of formed Ni/C powder as evidenced by TEM analysis. Nickel nanoparticles aggregation becomes more serious at longer microwave irradiation times. The electrocatalytic activity of different Ni/C samples towards glucose oxidation was studied in KOH solution by employing cyclic voltammetry and chronoamperometry techniques. Ni/C sample, prepared by pulse mode with total operating time of 150s, showed the highest oxidation current density. An excellent sensitivity value of 1349.7μAmM(-1)cm(-2) with a detection limit of 0.232μM was gained by Ni/C sensor. It also exhibits good reproducibility and long-term stability, as well as high selectivity with insignificant interference from ascorbic acid.

NiO nanoparticles on graphene nanosheets at different calcination temperatures as effective electrocatalysts for urea electro-oxidation in alkaline medium

NiO nanoparticles were supported on graphene nanosheets (NiO/Gr) through coprecipitation step of Ni(OH)2 species, followed by calcination at different temperature values. The formed nanocomposites were characterized by employing X-ray diffraction (XRD) and transmission electron microscopy (TEM) to investigate their crystalline structure and morphology. The effect of varying the calcination temperature during the preparation of NiO/Gr electrocatalyst on some kinetic parameters in 0.5M NaOH solution was studied. The electrocatalytic activity of synthesized electrocatalysts was examined for urea electro-oxidation reaction in alkaline solution using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Among the fabricated NiO/Gr electrocatalysts, the one that was heated at 200°C exhibited the highest urea oxidation current density value with most stable performance for long time.

Influence of Metal Oxides on Platinum Activity towards Methanol Oxidation in H2SO4 solution.

Pt-CeO2 /C, Pt-TiO2 /C, and Pt-ZrO2 /C electrocatalysts were prepared by using a modified microwave-assisted polyol process. Physical characterization was performed by using XRD, TEM, and EDX analyses. The incorporation of different metal oxides increased the dispersion degree of Pt nanoparticles and reduced their diameter to 2.50 and 2.33 nm when TiO2 and ZrO2 were introduced to Pt/C, respectively. The electrocatalytic activity of various electrocatalysts was examined towards methanol oxidation in H2 SO4 solution by using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Among the studied composites, Pt-ZrO2 /C was selected to be a candidate electrocatalyst for better electrochemical performance in direct methanol fuel cells.

Enhanced ethanol electro-oxidation reaction on carbon supported Pd-metal oxide electrocatalysts

Various Pd-metal oxide/C electrocatalysts were fabricated using ethylene glycol as a reducing agent in modified microwave-assisted polyol process. The crystal structure and surface morphology were studied using X-ray diffraction and transmission electron microscopy. All prepared Pd-metal oxide/C electrocatalysts exhibited a shift of Pd diffraction planes in the positive direction in relation to that of Pd/C. Highly dispersed palladium nanoparticles were formed on different metal oxide/C supports. The electrocatalytic performance of these electrocatalysts for ethanol oxidation was examined in NaOH solution using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. An improvement in electrochemical parameters including onset potential, oxidation current density and If/Ib values was recorded at different Pd-metal oxide/C electrocatalysts, especially Pd-NiO/C. Three folds increment in steady state oxidation current density value was also displayed by investigated Pd-metal oxide/C electrocatalysts when contrasted to that of Pd/C to reflect their enhanced stability behavior.

A core–shell structured Ni–Co@Pt/C nanocomposite-modified sensor for the voltammetric determination of pseudoephedrine HCl

Herein, a core–shell structured Ni–Co@Pt/C nanocomposite was developed for the determination of pseudoephedrine HCl (PSE) in drug samples. Different Ni–Co@Pt/C nanomaterials were fabricated by varying the Ni : Co atomic ratio using ethylene glycol as the reducing agent via an assisted microwave irradiation process. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were conducted to characterize the prepared nanocomposite. Electrocatalytic activity of the Ni–Co@Pt/C nanocomposite for the determination of PSE was demonstrated using cyclic voltammetry, linear sweep voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The PSE oxidation current density value was efficiently affected by the cobalt content in the fabricated Ni–Co@Pt/C nanocomposite. The maximum activity was achieved with the nanomaterial containing a Ni : Co atomic ratio of 1 : 3. Differential pulse voltammetry indicated a linear dependence of the oxidation current density on the PSE concentration up to 1400 μM. High sensitivity and good reproducibility and stability were displayed by the Ni–Co@Pt/C nanocomposite during the estimation of PSE. This would encourage the wide application of the proposed nanocomposite in the clinical assay of the studied drugs.

Synthesis and characterization of core–shell structured M@Pd/SnO2–graphene [M = Co, Ni or Cu] electrocatalysts for ethanol oxidation in alkaline solution

Core–shell structured M@Pd/SnO2–graphene (Gr), [M = Co, Ni or Cu] electrocatalysts were synthesized using ethylene glycol as a reducing agent with the aid of microwave irradiation in a two-step process. XRD, TEM and EDX analysis techniques were employed to physically characterize the prepared electrocatalysts. They revealed the formation of SnO2–Gr as a support, surrounded by M as a core that was coated with Pd as a shell. The M@Pd/SnO2–Gr electrocatalysts showed a gradual negative shift of their Pd(111) and Pd(200) diffraction peaks when compared to those in the XRD pattern of Pd/Gr. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were employed to investigate the electrocatalytic activity of the prepared electrocatalysts for ethanol oxidation in NaOH solution. Increased ECSA values were recorded at the M@Pd/SnO2–Gr electrocatalysts, especially Cu@Pd/SnO2–Gr [467.49 m2 g−1] in relation to that at Pd/Gr. The presence of cobalt, nickel or copper in the M@Pd/SnO2–Gr electrocatalyst improved the ethanol oxidation mass activity of Pd/Gr by 4.42, 4.78 or 5.84, respectively. A chronoamperometry test demonstrated enhanced electrochemical durability for the fabricated core–shell structured electrocatalysts. Lowered charge transfer resistance values were also measured at these electrocatalysts during the ethanol oxidation reaction. Based on the results in previous reports, core–shell structured Cu@Pd/SnO2–Gr is a potentially valuable electrocatalyst for fuel cell applications.

Influence of support material on the electrocatalytic activity of nickel oxide nanoparticles for urea electro-oxidation reaction

Nickel oxide nanoparticles were deposited on different carbon supports including activated Vulcan XC-72R carbon black (NiO/AC), multi-walled carbon nanotubes (NiO/MWCNTs), graphene (NiO/Gr) and graphite (NiO/Gt) through precipitation step followed by calcination at 400 °C. To determine the crystalline structure and morphology of prepared electrocatalysts, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed. The electrocatalytic activity of NiO/carbon support electrocatalysts was investigated towards urea electro-oxidation reaction in NaOH solution using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Urea oxidation peak current density was increased in the following order: NiO/AC < NiO/MWCNTs < NiO/Gr < NiO/Gt. Chronoamperometry test also showed an increased steady state oxidation current density for NiO/Gt in comparison to other electrocatalysts. The increased activity and stability of NiO/Gt electrocatalyst encourage the application of graphite as an efficient and cost-saving support to carry metal nanoparticles for urea electro-oxidation reaction.