Mohamed Mohamedi

Institut National de la Recherche Scientifique | INRS · Energy, Materials and Telecommunications Research Centre

Nanorod structures exhibit a high surface-to-volume ratio, enhancing the accessibility of electrolyte ions to the electrode surface and providing an abundance of active sites for improved electrochemical sensing performance. In this study, tetragonal α-MnO2 with a large K+-embedded tunnel structure, directly grown on microfibrous carbon paper to fo...

Efficient and sustainable energy storage remains a critical challenge in the advancement of energy technologies. This study presents the fabrication and electrochemical evaluation of a self-supporting electrode material composed of MnO2 nanorods grown directly on a carbon paper and carbon nanotube (CNT) substrate using a hydrothermal method. The re...

In this work, TiO 2 layers are synthetized on Ti6Al4V alloy substrate by electrochemical anodizing process in fluoride-containing alkaline electrolytes and under different applied voltages (10, 20, and 30 V). The scanning electron microscopy (SEM) reveals a nearly regular and vertical alignment of TiO 2 nanotubes (80-100 nm) for specimen treated at...

Infiltration of the mesoporous structure of SBA-15 silica as a hard template with phenanthroline complexes of Fe+3 and Co+2 allowed the simultaneous dispersion of nitrogen, iron and cobalt species on...

The rational design of the electrocatalysts is paramount to alleviating the global energy and environment crisis. Despite a bright future of MnO2 shown in energy storage and conversion, the intrinsic low electrical conductivity glooms its application in electrocatalytic reactions like oxygen reduction/evolution reactions (ORR/OER). The doping strat...

This work presents the hydrothermal synthesis of hierarchical TiO2 nanorods (NRs) grown for the first time from a pulsed laser deposited Ti seed layer on carbon paper (CP) substrate without the use of templates or binders. XRD reveals that TiO2-NRs crystallize in rutile phase. The as-prepared TiO2-NRs greatly enhances the electroactivity and stabil...

It is now recognized that the development of self-supported and efficient bifunctional air cathodes via the direct growth of earth-abundant catalysts onto the surface of the conductive collector would be a cutting-edge strategy to reduce interfacial resistance, enhance the mechanical tenure, and reduce the final weight and cost of manufacturing of...

A 3-D model is established by considering mass transport phenomena, electrochemical reactions, electrode porosity, air breathing at the cathode, electrodes properties, fluid density and fluid viscosity. The model is applied to μFFC V- and U-shaped microfluidic channels. The agreement between the experiments and simulation in terms of predicted pola...

We report here the synthesis of binderless and template-less three-dimensional (3D) pinecone-shaped Pt/TiO2/Ti mesh structure. The TiO2 hydrothermally synthesized onto Ti mesh is composed of a mixture of flower-like nanorods and vertically aligned bar-shaped structures, whereas Pt film grown by pulsed laser deposition displays a smooth surface. XRD...

The future of fuel cells technology will require porous or very organized multicomponent catalytic layers that can be prepared by thin film growth methods. Reducing the cost of these energy systems will also necessitate that the catalytic layers to be binderless and contain low amount of the noble catalyst at least until more efficient non‐noble ca...

The rational design of durable materials is an important issue for improving the performance of electrocatalysts towards the ethanol oxidation reaction (EOR). In this work, binderless thin nanostructured layers of SnO2, Pt, Rh, bilayers of Pt/SnO2, Rh/Pt and tri-layers of Rh (ca. 10 nm thickness)/PtSnO2 are directly grown by pulsed laser deposition...

Mixed-reactant microfluidic membraneless fuel cells are promising power sources for future electronic portable applications due to their simplified construction and operation. In order to develop a better performing mixed-reactant fuel cell, the improvement of elements such as selective catalysts and optimization of electrode-microchannel arrangeme...

By combining the hydrothermal and pulsed laser deposition methods, several three‐dimensional Pt catalysts on TiO2 structures are prepared and used for the electro‐oxidation of ethanol in acidic medium. SEM reveals that TiO2 prepared with 0.6 M of HCl consist of a mixture of nanowires and nanorods. For higher HCl concentrations, the TiO2 are either...

Carbon-supported rhodium thin films with various thicknesses are grown by varying the number of laser pulses, Nlp (from 5000 to 50,000) under 2 Torr of He background atmosphere using the pulsed laser deposition method. The thin films are characterized for their morphological features and structural properties. It is observed that smooth dense 2D na...

Plasmas techniques are novel routes for the preparation of complex nanostructured materials for catalysis and clean hydrogen energy such as fuel cells. CBPLD technique allows enhanced interaction between the catalyst and the support and improved catalytic properties. Herein, a highly active and durable vertically aligned nanostructured shrub-like b...

Zn-air battery is of great interest in rechargeable batteries due to its low cost, environment-friendly and theoretically high energy density which is about 1086 Wh kg ⁻¹ [1]. The activity and durability of cathode are the bottleneck of the battery performance, which attribute to the sluggish kinetics of the oxygen reduction reaction (ORR) during d...

An inorganic microfluidic fuel cell (i-μFFC) was integrated in a glucose sensor LOC device. This device was constructed by using a mini CNC and evaluated for energy harvesting from glucose. The i-μFFC with PLD electrodes exhibits the highest performance compared to the i-μFFC with spray electrodes microfluidic fuel cell for the three conditions, ob...

Microfluidic direct ethanol fuel cells are a promising technology for powering electronic portable devices in the future, and the use of efficient electrocatalysts, both anodic and cathodic are crucial for the development of this type of fuel cells. In this work, an Ag-Pt ethanol-tolerant cathode, synthesized by pulsed laser deposition is studied i...

Mixed-reactant microfluidic direct methanol fuel cells (MR-μDMFCs) have the feature of achieving higher volumetric energy density in comparison with other DMFCs. The main challenge for the development of MR-μDMFC arises from the need for selective electrocatalysts, especially for the oxygen reduction reaction (ORR). In the present work, we report t...

In this work, TiO2 layers are synthetized on Ti6Al4V alloy substrate by electrochemical anodizing process in fluoride‐containing alkaline electrolytes and under different applied voltages (10, 20, and 30 V). The scanning electron microscopy (SEM) reveals a nearly regular and vertical alignment of TiO2 nanotubes (≈80–100 nm) for specimen treated at...

The conversion of biomass waste into valuable carbon composites as efficient non-precious metal oxygen-reduction electrocatalysts is attractive for the development of commercially viable fuel-cell and metal-air battery technologies. Herein, a highly active and robust Si-contained Fe/N/C catalyst is prepared based on the porous carbon deriving from...

In the present work, we report the design, fabrication and evaluation of a membraneless mixed-reactant and air-breathing microfluidic direct methanol fuel cell (ML-μDMFC) stack operated in passive mode. The operation under mixed-reactant conditions was achieved by using a highly methanol-tolerant Ag/Pt/CP cathode with ultra-low Pt loading in alkali...

Pseudocapacitive materials are the basis of the emerging pseudocapacitors, but the applicability of this class of electroactive materials is not limited to supercapacitors. In fact, the pseudocapacitive behaviour of electrode materials is of particular importance in battery systems and electrocatalysis as well. Therefore, it is of vital necessity t...

The fabrication and evaluation of a passive, air-breathing, membraneless microfluidic direct methanol fuel cell (ML-μDMFC) using a methanol-tolerant Ag/Pt/CP cathode is presented here. We previously proposed that due to its high tolerance to methanol and the good activity towards the oxygen reduction reaction in alkaline medium, this catalyst could...

Titanium dioxide is emerging as new class of catalyst support for fuel cell reactions. Via pulsed laser deposition, we prepare hierarchically organized and vertically aligned TiO2/Pt nanostructured films on microfibrous carbon paper (CP) substrate at room temperature. Microstructural analyses reveal a metal-support interaction between TiO2 and Pt....

A strategy for the synthesis at room temperature of binderless 3D sphere-like aggregates of bimetallic PtRh nanoparticles onto carbon nanotubes (CNTs) by cross-beam laser deposition technique is presented. The atomic ratio between the two components (Pt and Rh) is tuned by varying the laser pulse energy on the two targets independently to optimize...

MnOx thin films with various oxidation states (MnO, Mn2O3, MnO2 and mixed MnO/Mn3O4) were directly grown onto carbon nanotubes by pulsed laser deposition under vacuum and at different oxygen partial pressures. The microstructural features of the as-deposited thin films are characterized by scanning electron microscopy and X-ray photoelectron spectr...

In the present work, we report the synthesis by pulsed laser deposition technique of binder-free platinum layer coated with silver layer, with each layer having a thickness of about 25 nm. The resulting Pt/Ag material exhibits clear electrocatalytic activity for oxygen reduction reaction (ORR) in alkaline solution. More interestingly, it shows no a...

In the present work, we report an ethanol tolerant cathode catalyst developed through a two-stages electrodeposition of Pt and Ag nanoparticles on a glassy carbon electrode using chronoamperometric and voltammetric techniques. The resulting nanoparticles were characterized by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), X-Ray Photoe...

Pt-transition metal oxides are emerging as new class of electrodes for alcohol oxidation reactions. We prepare at room temperature Pt-SnO2 nanocomposites of various surface morphologies onto carbon nanotubes for enhanced ethanol oxidation reaction (EOR) by cross-beam pulsed laser deposition technique. Synthesized nanocomposites are characterized by...

Highly-ordered microporous carbon (MPC) nanospheres were prepared by a simple hydrothermal route based on a soft template. The interlayer spacing of the MPC was well tuned by simply adjusting the heat-treatment temperatures. The as-obtained carbon spheres treated at 700 °C (MPC-700) combine the features required for high-performance sodium-ion batt...

A binderless ternary catalyst layer of CNT (carbon nanotubes)/(Pt-MnO2) is presented. The (Pt-MnO2) nanocomposites with different surface morphology are directly grown for the first time onto CNTs at room temperature through cross-beam pulsed laser deposition method and their electroactivity in sulfuric acid and towards ethanol electrooxidation are...

Ethanol is an attractive fuel for direct ethanol fuel cells (DEFCs) because it has high theoretical energy density (8.0 kWh/kg) [1], it is nontoxic and can be produced from biomass, which could make DEFCs beneficial low greenhouse gas emission power sources. Platinum is known to be the most active catalyst for the ethanol oxidation reaction (EOR)....

Titanium dioxide is cheap, non-toxic, exhibits a high mechanical resistance, very stable in acidic and oxidative environments is being studied as alternative to carbon as catalyst support in low-temperature fuel cells. Herein, via pulsed laser deposition, various morphologies of TiO2 thin films are synthesized at room temperature onto conductive mi...

In this work, we report for the first time the use of tungsten oxide (WOx) as catalyst support for Au toward the direct electrooxidation of glucose. The nanostructured WOx/Au electrodes were synthesized by means of laser-ablation technique. Both micro-Raman spectroscopy and transmission electron microscopy showed that the produced WOx thin film is...

XPS survey scan of Au deposited onto WOx. Abbreviations: WOx, tungsten oxide; XPS, X-ray photoelectron spectroscopy.

Electrochemical studies of glucose detection and sensitivity. Notes: (A) Chronoamperometry measurements at an applied potential of 0.25 V vs Ag/AgCl at the Au-WOx electrode in argon-saturated 0.01 M PBS solution at pH 7.2 containing concentrations of glucose varying from 0 mM to 100 mM; (B) the dependence of the steady-state current density over th...

Electrochemical studies of glucose detection and sensitivity. Notes: (A) Voltammetry measurements recorded with 2 mV second−1 at the Au-WOx electrode in argon-saturated 0.01 M PBS solution at pH 7.2 containing concentrations of glucose varying from 0.01 mM to 100 mM; (B) the dependence of the peak current density over the whole range of glucose con...

XPS survey scan of WOx deposited onto carbon paper. Abbreviations: XPS, X-ray photoelectron spectroscopy; WOx, tungsten oxide.

Here, we present for the first time Au-CeO2 nanocomposite synthesized in presence of mild pressure of oxygen (10 mTorr) by means of the cross-beam laser deposition technique. The deposit was grown on a conductive (current collector) substrate made of a porous network of carbon microfibers. The structure and morphology of the deposit were characteri...

We report on the fabrication of nanostructured CeO2-gold electrodes by means of laser ablation. The synthetic conditions were varied in order to obtain different morphologies of CeO2. The physical and chemical properties of the samples were studied by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The effect...

Here, we present for the first time an Au–CeO2 nanocomposite synthesized in the presence of a mild pressure of oxygen (1.33 Pa) by the cross-beam laser deposition technique. The deposit was grown on a conductive (current collector) substrate composed of a porous network of carbon microfibers. The structure and morphology of the deposit were charact...

The non-enzymatic cyclic and pulse voltammetric detection of glucose using pulsed laser deposited gold nanostructures onto carbon nanotubes electrodes is described for the first time. Several synthesis conditions have been considered in order to obtain various morphologies for the Au film. Among all the synthesized Au nanostructures, it is found th...

Ceria has a high isoelectric point (IEP~9.2) and its cerium atom reversibly undergoes oxidation/reduction process therefore theoretically capable through electrostatic interactions of immobilizing enzymes with lower IEP and of electrons mediating, respectively. Based on this theoretical bi-functional role, we synthesized nano CeO2 by pulsed laser d...

Rh thin films have been synthesized onto carbon nanotubes by pulsed laser deposition under vacuum and under 266 Pa of helium background pressure. Field emission scanning electron microscopy revealed two types of Rh films: (i) Rh film fabricated under vacuum was smooth and of closed structure and (ii) Rh prepared at 266 Pa of He was porous. Transmis...

With the objective of lowering the potential oxidation of ethanol at PtSn nanocatalyst, we present the synthesis of free-standing catalyst layer comprising a current collector/carbon nanotubes (catalyst support)/SnO2/Pt75Sn25 (catalyst) nanostructured layers, each layer constructed upon the one below it. The CNTs are grown by chemical vapor deposit...

This work reports a comprehensive electroanalytical study of carbon nanohorns (CNHs) in electrochemical applications. Compared to other types of carbons, the bare CNHs electrode exhibited higher peak current densities and lowest anodic peak‐to‐cathodic peak separation of less than 50 mV for the [Fe(CN)4−]6/[Fe(CN)3−]6 redox couple. Furthermore, CNH...

This work demonstrates an approach for building bioelectrocatalytic interfaces by electrochemically functionalizing carbon nanotubes surface to create a conductive matrix for immobilization of enzymes. Such a strategy not only is simple but presents an opportunity to intimately interface an enzyme and manifests direct electron transfer features. El...

This work discusses the effect of the carbon morphology in binderless nanostructured Pt catalyst on the oxygen reduction reaction (ORR). In summary, we have examined five type of carbon, the carbon paper (CP), carbon sphere chains (CSC), carbon nanofibers (CNF), carbon nanotubes (CNT) and carbon nanohorns (CNH). On the surface of each carbon, Pt wa...

We present a free-standing catalyst layer comprising current collector/CNTs (catalyst support)/CeO(2)/Pt (catalyst) nanostructured layers, each layer constructed upon the one below it. FESEM and TEM showed that a CeO(2) layer has a fluffy morphology recalling the texture of cotton, whereas Pt nanoparticles assemble into cauliflower or broccoli-like...

The pulsed laser deposition has been used to synthesize Pt nanostructured films onto carbon paper substrate. In summary, we have examined the change occurring in structural characteristics of Pt thin films grown in a He background gas and in vacuum. The electrochemical studies showed that Pt deposited under 5 Torr of He background pressure displaye...

We report the synthesis of an advanced carbon paper (CP) macro-substrate (current collector)/carbon nanotubes (catalyst support)/Pt75Sn25 (nanocatalyst) architecture. The Pt75Sn25 was synthesized onto carbon nanotubes by mean of the cross-beam laser deposition (CBLD) technique. By varying the background gas pressure in the deposition chamber, smoot...

We present a concept of binderless nanothin catalyst layers for low power sources applications such as micro-fuel cells. The catalyst layer (CL) consists of pure CNTs catalyst support fabricated using chemical vapor deposition technique and a catalyst deposited by the pulsed laser deposition method. The whole CL is fabricated onto an electrically c...

Electrochemical functionalization via electrochemical oxidation in nitric acid of various concentrations (0.1 M, 0.2 M and 2 M) was employed to enrich the surface of carbon sphere chains (CSCs) with some useful physico‐chemical properties such as hydrophilicity, oxygen functionalities and electron transfer properties. The functionalization process...

In this work, we report the synthesis and characterization of nanoscaled CNT/SnO 2 /Pt films. The SnO 2 and Pt films were deposited using the pulsed laser deposition technique. Films of nanometric thicknesses of 17 nm and 40 nm for SnO 2 and Pt, respectively were obtained. SEM, TEM and XPS analysis all confirmed that each film was evenly coating th...

In this article, we report on the use of a pulsed KrF-laser (248 nm, 20 ns) for the synthesis of single wall carbon nanotubes (SWCNTs) from the ablation of a graphite target loaded with Co/Ni catalyst, under various growth conditions. By varying the Co/Ni catalyst load of the graphite target, from 0 to 2.4 at.%, the laser synthesized SWCNTs, under...

Rhodium nanostructured thin film catalysts were prepared by pulsed laser deposition. The depositions were performed under vacuum and at different He background gas pressures ranging from 1 to 5Torr. SEM, TEM, X-ray diffraction, and X-ray photoelectron spectroscopy were used to evaluate the morphology, the structure, the surface composition, and the...

An advanced carbon paper (CP) macro-substrate (current collector)/submicro-carbon sphere chains, CSCs (catalyst support)/Au (nanocatalyst) architecture was designed and constructed. Gold was deposited onto the surface of CSCs (several microns in length) through pulsed laser deposition to produce a porous ultra-thin film. In sulfuric acid solution,...

Solid carbon spheres chains (CSCs) are new carbon materials with unique physicochemical properties and original organization, they present a distinctive opportunity for creating novel multifunctional composites electrodes for a wide range of electrochemical applications. The electrocatalytic supporting of properties of these CSCs-coated with a mode...

Binderless carbon nanotubes aerogel (CNAG) composites represent a new class of high-performing electrodes for energy storage applications such as electrochemical double layer capacitors. The composites developed here differ significantly from these previously prepared with dispersion processes. The CNAG material was prepared by a molding procedure...

Similar to conventional composite electrodes, developing binderless-based carbon nanostructured (CNs) electrodes for fuel cells requires particularly the optimisation of both the morphology and the density of the CNs. In this work, carbon nanofibers (CNFs) have been optimised and used as catalyst support for Pt nanoparticles (NPs). The nontrivial r...

We report on the significant generation of photocurrent (PC) from planar devices built from the drop casting of UV-laser-synthesized single-wall-carbon-nanotubes (SWCNTs) onto n-Si substrate. These SWCNTs/n-Si hybrid devices are shown to generate PC with external quantum efficiencies (EQE) reaching up to ∼ 10%. Their EQE has been optimized by contr...

In this work, we introduce the on-substrate preparation and characterization of ultra highly densely packed sub-micrometer carbon of perfect sphericity and well-connecting to each other forming chainlike compounds. These carbon sub-microsphere (CSMS) chains are highly pure with no catalyst remaining encapsulated within their core as revealed by tra...

Nanostructured Pt thin film catalysts of various morphologies have been synthesized by pulsed laser deposition and studied towards enhancing their tolerance to CO poisoning, a reaction of critical issue to liquid fuel cells. It was discovered that Pt film deposited under 5 Torr of He background pressure showed the highest electroactive surface area...