Browsing by Author "Hadjersi, Toufik"

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Diamond-Like carbon - coated silicon nanowires as a supercapacitor electrode in an aqueous LiClO4 electrolyte
(Springer, 2021) Rachedi, Nacera; Hadjersi, Toufik; Moulai, Fatsah; Dokhan, Nahed
Silicon nanowires (SiNWs) were successfully coated by uniform, adherent, and homogenous films of diamond-like carbon(DLC) using electrophoretic method. The coating was performed in an organic dimethylsulfoxide (DMSO) solution at 70 °Cfor 60 min with an applied voltage of 150 V. The as prepared samples of SiNWs and DLC/SiNWs were characterized by ascanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), and Raman spectroscopytechniques. The SEM micrographics showed that the films were uniformly deposited on the whole of SiNWs surface andcomposed of compact and small spherical grains with uniform distribution. Raman spectroscopy indicates that the coating filmswere DLC in nature. These results were well confirmed by the EDX and XRD techniques. The electrochemical investigationincluding cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy, showed that theelectrochemical behavior of SiNWs was clearly enhanced after coating with a DLC film. Indeed, the latter showed a specificcapacitance of 400 mF/cm2at scan rate of 5 mV/s in an aqueous 0.5 M LiClO4solution with capacitance retention of 90% after16,000 cycles. Thus, the deposition of DLC film onto silicon nanowires (SiNWs) substrate can be considered as a simple andeconomical method to fabricate a high-performance electrode for supercapacitors
An estimate of a frequency characterizing the electrochemical stability of a gold electrode modified by MHDA thiol in different ways
(Croatian Chemical Society, 2021) Chaibi, Sarah; Zabat, Mokhtar; Hadjersi, Toufik; Abaidia, Seddik-El-Hak; Zine, Nadia; Yaakoubi, Nourdin; Errachid, Abelhamid
A theoretical investigation aimed at estimating a characteristic frequency in the medium-low frequency domain in which the impedance response of a given interface measured by electrochemical impedance spectroscopy (EIS) is almost constant, constitutes the basic idea of this work. A theoretical model was subsequently applied to the data resulting from EIS measurements performed on gold electrodes modified by various ways of 16-mercaptohexadecanoic acid (MHDA) thiol functionalization. Analysis of these data revealed a direct relationship between the way the substrate was modified and this characteristic frequency
High performance silicon nanowires/ruthenium nanoparticles micro-supercapacitors
(Elsevier, 2019) Bencheikh, Yasmina; Harnois, Maxime; Jijie, Roxana; Addad, Ahmed; Roussel, Pascal; Szunerits, Sabine; Hadjersi, Toufik; Abaidia, Seddik-El-Hak; Boukherroub, Rabah
The continuous increase of small electronic devices calls for small energy storage components, commonly known as micro-supercapacitors, that can ensure autonomous operation of these devices. In this work, we propose a simple and straightforward method to achieve high energy and power densities of a silicon-based micro-supercapacitor, consisting of silicon nanowires decorated with ruthenium nanoparticles (Ru/Si NWs). The Si NWs are obtained through the common vapor-liquid-solid (VLS) growth mechanism, while a simple electroless process is used to deposit Ru nanoparticles. While silicon nanostructuration allows to increase the surface area, coating with Ru NPs introduces a pseudocapacitance necessary to attain high energy and power densities. The Ru/Si NWs micro-supercapacitor exhibits a specific capacitance of 36.25 mF cm−2 at a current density of 1 mA cm−2 in a neutral Na2SO4 electrolyte and a high stability over 25 000 cycles under galvanostatic charge-discharge at 1 mA cm−2. A solid state supercapacitor is then fabricated with symmetric electrodes separated by a polyvinyl alcohol/sulfuric acid electrolyte. The device displays a specific capacitance of ∼18 mF cm−2 at a current density of 1 mA cm−2 and a specific power density 0.5 mW cm−2. This solid-state nanowire device also exhibits a good stability over 10 000 galvanostatic charge-discharge cycles
MnO2 decorated Silicon Nanowires: A novel photocatalyst for improved Rhodamine B removal under visible light exposure
(Elsevier, 2024) Derkaoui, Khaled; Bencherifa, Ismail; Hadjersi, Toufik; Belkhettab, Ilyas; Boukhouidem, K.; Bouanik, Sihem Aissiou; Brik, Afaf; Kechouane, Mohamed; Kaci, Mohamed Mehdi
Pollution triggered by organic dyes is a prominent global concern. Thus, it is imperative to devise an effective preventative strategy to tackle this matter. Herein, using the chemical electroless deposition process, a novel SiNWs/MnO2 photocatalyst was successfully manufactured for efficacious photocatalytic purification under visible lighting. Through a series of characterization techniques, the structural, morphological, compositional, and optical features of MnO2-deposited silicon nanowires were thoroughly investigated. The photocatalytic ability of the resultant sample was reckoned by degrading Rhodamine B upon visible exposure. Following 180 min of brightness, the findings found that SiNWs/MnO2 displayed remarkable effectiveness, with a lessening of 93.4 %. The findings demonstrated a significant enhancement in degradation performance linked to the rising surface area and enhanced electron-hole segregation efficiency provided by silicon nanowires. Also, the sample's recyclability was assessed, exhibiting an encouraging sustainability with a slight fall in effectiveness (∼10%) after 6 straight utilizes. Furthermore, scavenging tests have shown that •OH and •O2− were prevalent species accountable for the RhB degradation reaction. Eventually, founded on the results, a plausible mechanism for RhB decomposition was suggested. Altogether, given the straightforward manufacturing method and impressive performance, the study argues that the novel SiNWs/MnO2 might be an intriguing photocatalyst for water contaminant remediation.
Silicon nanowire-hydrogenated TiO2 core-shell arrays for stable electrochemical micro-capacitors
(Elsevier, 2021) Bencheikh, Yasmina; Addad, Ahmed; Coffinier, Yannick; Kumar, Umesh; Roussel, Pascal; Szunerits, Sabine; Hadjersi, Toufik; Amin, Mohammed A.; Abaidia, Seddik-El-Hak; Boukherroub, Rabah
In this paper, we fabricated silicon nanowire-TiO2 core-shell arrays in a two-step process. First, silicon nanowire arrays (SiNW) were prepared in HF/AgNO3 aqueous solution using metal-assisted chemical etching of bulk silicon. Then, atomic layer deposition (ALD) technique was applied to coat a 20 nm thin shell TiO2 film. The TiO2/SiNW substrates were afterward annealed at 400°C in hydrogen atmosphere for 4 h and tested as electrode materials for electrochemical micro-capacitors. The electrochemical features of the constructed H−TiO2/SiNW electrode were assessed in an aqueous 1 M Na2SO4 electrolyte solution and revealed that the specific capacitance increased six times compared to non-annealed TiO2/SiNW and 20-fold compared to a reference SiNW electrode under the same operating conditions. Importantly, H−TiO2/SiNW also displayed a high stability over 30,000 cycles at 0.1 mA cm−2 with an overall decrease of 19% of the initial capacitance. The hydrogen treatment increased the density of hydroxyl group and enhanced the carrier density on TiO2 surface improving the capacitive properties of H−TiO2/SiNW
Ternary WO₃–MnO₂@SiNWs hybrid electrodes for high-performance Micro-supercapacitors with enhanced energy density and stability
(Elsevier, 2025) Boukhouidem, Khadidja; Slimani, Amel; Derkaoui, Khaled; Manfo, Theodore Azemtsop; Hadjersi, Toufik; Manseri, Amar; Selmi, Noureddine; Elhak Abaidia, Seddik
Advanced energy storage technologies, such as rechargeable Batteries and Micro-supercapacitors (μSCs) play a pivotal role in addressing the growing global energy demand. Improving their energy and power densities requires the development of electrode materials with well-engineered, hierarchical porous architectures. In this work, we report a facile hydrothermal synthesis of WO₃-MnO₂ composite nanostructures directly integrated onto silicon nanowires (SiNWs), which serve as a highly conductive and high-surface-area scaffold. The influence of annealing temperature on the structural, morphological, and electrochemical properties of the WO₃-MnO₂@SiNWs composite was systematically investigated. Structural characterization through X-ray diffraction (XRD) and surface analysis via X-ray photoelectron spectroscopy (XPS) confirmed the successful formation of the hybrid oxide network. Furthermore, scanning electron microscopy (SEM) revealed a homogeneous distribution of the nanostructured composite coating over the vertically aligned SiNWs, forming a porous, interconnected network favorable for ion diffusion. Energy-dispersive X-ray spectroscopy (EDX) mapping confirmed the uniform presence of W, Mn, O, and Si elements throughout the electrode, indicating successful and consistent deposition of the WO₃-MnO₂ layers. The optimized electrode exhibited excellent capacitive performance, delivering a specific capacitance (Csp) of 16.56 mF·cm−2, an energy density (Ed) of 0.0001 Wh·cm−2, and a power density (Pd) of 0.024 W·cm−2, along with long-term cycling stability retaining 84 % of its initial capacitance over 4000 charge–discharge cycles. Additionally, electrochemical impedance spectroscopy revealed a consistent Csp of 14.23 mF·cm−2over a wide frequency range (0.01 Hz–1 MHz), indicating efficient charge transfer and low internal resistance. A solid-state symmetric μSC device constructed using WO₃-MnO₂@SiNWs electrodes further demonstrated impressive performance, achieving a maximum specific capacitance of 96 mF·cm−2at a scan rate of 2 mV·s−1, with 85 % capacitance retention over 2300 cycles and an energy density of 0.0028 Wh·cm−2at a power density of 0.4 W·cm−2. These remarkable electrochemical properties are attributed to the synergistic effects of multivalent WO₃ and MnO₂ species combined with the high conductivity and mechanical stability of the SiNWs framework, highlighting the potential of this composite architecture for next-generation on-chip energy storage devices.
Tetracycline Degradation Under Visible Light Using a New SiNW/CeO2/NiO Composite as a High-Efficiency Photocatalyst
(Springer, 2025) Brik, Afaf; Hadjersi, Toufik; Khaled, Derkaoui; Naama, Sabrina; Bendadel, Karima; Souraya, Bouachma; Benredouane, Soumia; Khadija, Boukhouidem
Recently, extensive research has focused on the purification of antibiotic-contaminated wastewater via photocatalysis techniques. In this context, many types of photocatalysts have been studied. In this work, silicon nanowires (SiNWs) were synthesized and coated with nickel oxide (NiO) and cerium oxide (CeO2) via a hydrothermal technique and used as new photocatalysts to degrade a recalcitrant antibiotic, namely, tetracycline (TC), under visible light irradiation. The prepared samples were characterized by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–Vis spectrophotometry (UV–Vis). These characterizations revealed that SiNWs are well coated over their entire length with NiO and CeO2. A 96% degradation rate of TC was achieved within 120 min under visible light irradiation. This enhanced performance is attributed to improved visible light absorption, efficient charge generation, and better charge separation and transfer enabled by the synergistic effects among SiNWs, CeO2, and NiO. The primary species involved in TC degradation were determined by radical scavenging tests to be e⁻, ⋅OH, O2⋅-, and h⁺, which allowed to suggest a reaction mechanism. Finally, this work proposes a new approach to synthesize a powerful photocatalyst that is able to eliminate emerging contaminants from the aquatic environment