Browsing by Author "Idiri, Naima"

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Cyclic voltammetry and galvanostatic effect on prepared Polypyrrole/Ni0.3Co2.7O4 for O2 electrocatalysis
(Institute of Physics Publishing, 2019) Belkessam, Celia; Mechouet, Mourad; Idiri, Naima; Ghilane, Jalal; Djelali, Nacer-Eddine
Ni0.3Co2.7O4 oxide embedded Polypyrrole (Ppy) thin films were successfully synthesized over glassy carbon disk (GC) part of rotating ring disk electrode (RRDE) by two different electropolymerisation route i.e. galvanostatic (GS) and multi-cyclic voltammetry (CV), from a solution containing 0.1 mol L -1 pyrrole (Py) and 7 g L -1 of Ni0.3Co2.7O4. The Ppy electrodeposition signal has been studied by varying two parameters i.e. the oxide nanoparticles (NPs) presence and the preparation method. In addition, the obtained hybrid electrode morphology, stability especially in methanol presence, and electrocatalytic activity towards the oxygen reduction reaction (ORR) have been also investigated. The results reveal that the obtained films properties have been affected by the used route and furthermore by the oxide addition. The CV shape was maintained in the NPs presence, however the reversibility behavior was better, since the potential gap between doping/dedoping processes became closer and its corresponding currents are significantly risen. The two synthesis methods lead to hybrids electrodes with pronounced ORR electrocatalytic activity. Thus, the GS obtained material exhibits a weak selectivity regarding electrons exchanged number and the H2O2 produced amount was only about 50%. However, these interesting properties were enhanced i.e. mainly 2 electrons were exchanged by producing 96% of H2O2, when the composite electrode was prepared by CV route. Moreover, this catalyst has good stability, as well as a higher tolerance to methanol for relative long time. Therefore, the CV method can be very useful on conducting polymer/NPs materials synthesis for environmental applications requiring peroxides use
The Effect of Heteroatom Doping on Nickel Cobalt Oxide Electrocatalysts for Oxygen Evolution and Reduction Reactions
(2020) Belkessam, Celia; Bencherif, Selma; Mechouet, Mourad; Idiri, Naima; Ghilane, Jalal
The synthesis of nickel cobalt oxide materials and their electrocatalytic performance toward the oxygen reduction and evolution reactions are reported. Nickel cobalt oxides were synthesized in a sol‐gel process with different precursors, namely nitrate, sulfate, and chloride. Structural analyses show that the structures have mesoporous morphologies and indicate the formation of nickel cobalt oxide spinel structures with a size ranging from 35 to 65 nm. Furthermore, the physicochemical properties differ depending on the nature of the selected precursors, including the materials’ morphology and the chemical composition. Electrocatalytic investigations demonstrate that the catalytic activity toward the oxygen reduction reaction (ORR) could be modulated between two‐ and four‐electron pathways, depending on the precursors used. The Cl−NiCoO sample displays a selective two‐electron reduction of O2, with H2O2 production higher than 90 %. The sample prepared using sulfate displays the highest performance toward the oxygen evolution reaction (OER), with a low overpotential value (0.34 V) to drive a current density of 10 mA.cm−1. Overall, these results confirm that the chemical composition of the precursor used during the nanomaterials synthesis can be used to tune the electrocatalytic performances toward ORR and OER