Search Results (48)

Simultaneous quantification of ascorbic acid, dopamine, and uric acid is crucial for clinical diagnostics. Here, an electrochemical sensor was developed by modifying a glassy carbon electrode with a ternary composite of multi-walled carbon nanotubes, graphene, and Vulcan XC72 carbon black via a simple mixing method. The synergistic interaction of these carbon materials significantly increases the electroactive surface area and introduces defect-driven catalytic sites, enhancing electron transfer kinetics. The sensor enables interference-free simultaneous detection, exhibiting linear ranges of 100–1000 μM ascorbic acid, 5–50 μM dopamine, and 10–100 μM uric acid with sensitivities of 0.044, 0.47, and 0.95 μA μM⁻¹, respectively, and corresponding limits of detection of 34.1, 4.23, and 11.1 μM. The platform also demonstrated excellent stability, reproducibility, and anti-interference performance, with satisfactory recoveries in human urine samples. These results highlight the ternary composite sensor as a reliable and practical tool for multiplexed monitoring in complex physiological matrices. Full article

In this study, we report the synthesis, characterization, and performance evaluation of a series of bimetallic Pt_xRh_y/C electrocatalysts with systematically varied Rh content for glycerol electrooxidation in acidic and alkaline media. The catalysts were prepared via a polyol reduction method using ethylene glycol as both a solvent and reducing agent, with prior functionalization of Vulcan XC-72 carbon to enhance nanoparticles (NPs) dispersion. High-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analyses indicated the spatial co-location of Rh atoms alongside Pt atoms. Electrochemical studies revealed strong composition-dependent behavior, with Pt₉₅Rh₅/C exhibiting the highest activity toward glycerol oxidation. To elucidate the origin of raised results, density functional tight binding (DFTB) simulations were conducted to model atomic distributions and evaluate energetic parameters. The results showed that Rh atoms preferentially segregate to the surface at higher concentrations due to their lower surface energy, while at low concentrations, they remain confined within the Pt lattice. Among the series, Pt₉₅Rh₅/C exhibited a distinctively higher excess energy and less favorable binding energy, rationalizing its lower thermodynamic stability. These findings reveal a clear trade-off between catalytic activity and structural durability, highlighting the critical role of the composition and nanoscale architecture in optimizing Pt-based electrocatalysts for alcohol oxidation reactions. Full article

The development of effective catalysts for the oxygen reduction reaction (ORR) is crucial for improving the performance of fuel cells. Efficient carbon-supported Pt-Co nanocatalysts were successfully prepared by a generic two-step method: (i) electroless deposition of a Co-P coating on Vulcan XC72R carbon powder and (ii) subsequent spontaneous partial galvanic replacement of Co by Pt, upon immersion of the Co/C precursor in a chloroplatinate solution. The prepared Pt-Co particles (of a core-shell structure) are dispersed on a Vulcan XC-72 support, forming agglomerates made of nanoparticles smaller than 10 nm. The composition and surface morphology of the samples were characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS) as well as transmission electron microscopy (TEM). The crystal structures of the Co-P/C precursor and Pt-Co/C catalyst were investigated by X-ray diffraction (XRD). XPS analysis was performed to study the chemical state of the surface layers of the precursor and catalyst. The electrochemical behavior of the Pt-Co/C composites was evaluated by cyclic voltammetry (CV). Linear sweep voltammetry (LSV) experiments were used to assess the catalytic activity towards the ORR and compared with that of a commercial Pt/C catalyst. The Pt-Co/C catalysts exhibit mass-specific and surface-specific activities (of j_m = 133 mA mg⁻¹ and j_esa = 0.661 mA cm⁻², respectively) at a typical overpotential value of 380 mV (+0.85 V vs. RHE); these are superior to those of similar electrodes made of a commercial Pt/C catalyst (j_m = 50.6 mA mg⁻¹; j_esa = 0.165 mA cm⁻²). The beneficial effect of even small (<1% wt.%) quantities of Co in the catalyst on Pt ORR activity may be attributed to an optimum catalyst composition and particle size resulting from the proposed preparation method. Full article

One of the key challenges in commercializing proton exchange membrane (PEM) electrolyzer technology is reducing the production costs while maintaining high efficiency and operational stability. Significant contributors to the overall cost of the device are the electrode catalysts with IrO₂ and Pt/C. Due to the high cost and limited availability of noble metals, there is growing interest in developing alternative, low-cost catalytic materials. In recent years, two-dimensional transition metal dichalcogenides (2D TMDCs), such as molybdenum disulfide (MoS₂) and rhenium disulfide (ReS₂), have attracted considerable attention due to their promising electrochemical properties for hydrogen evolution reactions (HERs). These materials exhibit unique properties, such as a high surface area or catalytic activity localized at the edges of the layered structure, which can be further enhanced through defect engineering or phase modulation. To increase the catalytically active surface area, the investigated materials were deposited on a carbon-based support—Vulcan XC-72R—selected for its high electrical conductivity and large specific surface area. This study investigated the physicochemical and electrochemical properties of six catalyst samples with varying MoS₂ and ReS₂ to carbon support ratios. Among the composites analyzed, the best sample on MoS₂ (containing the most carbon soot) and the best sample on ReS₂ (containing the least carbon soot) were selected. These were then used as cathode catalysts in an experimental PEM electrolyzer setup. The results confirmed satisfactory catalytic activity of the tested materials, indicating their potential as alternatives to conventional noble metal-based catalysts and providing a foundation for further research in this area. Full article

The anodic stability of tungsten carbide (WC) and iron oxide with a spinel structure (Fe₃O₄) were compared against similar data for nanostructured, boron-doped diamond (BDD), and the benchmark Vulcan XC72 carbon, in view of their eventual application as alternative supports for the anion exchange membrane electrolyzer anode. To this end, metal oxide composites were prepared by the in situ autocombustion (ISAC) method, and the anodic behavior of materials (composites as well as supports alone) was investigated in 1 M NaOH electrolyte by the rotating ring–disc electrode method, which enables the separation oxygen evolution reaction and materials’ degradation currents. Among all supports, BDD has proven to be the most stable, while Vulcan XC72 is the least stable under the anodic polarization, with Fe₃O₄ and WC demonstrating intermediate behavior. The Co₃O₄-BDD, -Fe₃O₄, -WC, and -Vulcan composites prepared by the ISAC method were then tested as catalysts of the oxygen evolution reaction. The Co₃O₄-BDD and Co₃O₄-Fe₃O₄ composites appear to be competitive electrocatalysts for the OER in alkaline medium, showing activity comparable to the literature and higher support stability towards oxidation, either in cyclic voltammetry or chronoamperometry stability tests. On the contrary, WC- and Vulcan-based composites are prone to degradation. Full article

Finding alternatives to platinum that exhibit high activity, stability, and abundant reserves as oxygen reduction electrocatalysts is crucial for the advancement of fuel cells. In this study, we first mixed FeCl₂·4H₂O, 1,10-phenanthroline, and Vulcan XC-72, followed by pyrolysis in a nitrogen atmosphere, to obtain FeNC. Subsequently, we combined FeNC with MXene produce FeNC/MXene composites. The FeNC/MXene catalyst achieved a half-wave potential of 0.857 V in an alkaline medium, exhibiting better oxygen reduction reaction (ORR) activity and durability than commercial Pt/C catalysts. The layered structure of MXene endows the material with a high specific surface area and facilitates efficient electron transfer pathways, thereby promoting rapid charge transfer and material diffusion. The cleavage of Ti-C bonds in Ti₃C₂ at elevated temperatures results in the transformation of MXene into TiO₂, where the coexistence of anatase and rutile phases generates a synergistic effect that enhances both the mass transfer rate and the electrical conductivity of the catalytic layer. Additionally, the unique electronic structure of the FeN_x sites simultaneously optimizes electrocatalytic activity and stability. Leveraging these structural advantages, the FeNC/MXene composite catalysts demonstrate exceptional catalytic activity and long-term stability in oxygen reduction reactions. Full article

This work reports the synthesis of PdNi bimetallic particles and Pd on Carbon black (Vulcan XC-72) by reverse microemulsion and the chemical reduction of metallic complexes. The physicochemical characterization techniques used for the bimetallic and metallic materials were TGA, STEM, ICP-OES, and XRD. Also, the electrocatalysts were studied by electrochemical techniques such as anodic CO stripping and β-NiOOH reduction to elucidate the Pd and Ni surface sites participation in the reactions. The electrocatalysts were evaluated in the anodic reaction in anion-exchange membrane fuel cells (AEMFC) and the hydrogen oxidation reaction (HOR) in alkaline media. The results indicate that PdNi/C electrocatalysts exhibited higher electrocatalytic activity than Pd/C electrocatalysts in both the half-cell test and in the AEMFC, even with the same Pd loading, which is attributed to the bifunctional mechanism that provides OH^- groups in oxophilic sites associated to Ni, that can facilitate the desorption of Hads in the Pd sites for the bimetallic material. Full article

The use of hydrogen as fuel presents many safety challenges due to its flammability and explosive nature, combined with its lack of color, taste, and odor. The purpose of this paper is to present an electrochemical sensor that can achieve rapid and accurate detection of hydrogen leakage. This paper presents both the component elements of the sensor, like sensing material, sensing element, and signal conditioning, as well as the electronic protection and signaling module of the critical concentrations of H₂. The sensing material consists of a catalyst type Vulcan XC72 40% Pt, from FuelCellStore, (Bryan, TX, USA). The sensing element is based on a membrane electrode assembly (MEA) system that includes a cathode electrode, an ion-conducting membrane type Nafion 117, from FuelCellStore, (Bryan, TX, USA). and an anode electrode mounted in a coin cell type CR2016, from Xiamen Tob New Energy Technology Co., Ltd, (Xiamen City, Fujian Province, China). The electronic block for electrical signal conditioning, which is delivered by the sensing element, uses an INA111, from Burr-Brown by Texas Instruments Corporation, (Dallas, TX, USA). instrumentation operational amplifier. The main characteristics of the electrochemical sensor for hydrogen leakage detection are operation at room temperature so it does not require a heater, maximum amperometric response time of 1 s, fast recovery time of maximum 1 s, and extended range of hydrogen concentrations detection in a range of up to 20%. Full article

This work aims at the effects of anion-exchange membranes (AEMs) and ionomer binders on the catalyst electrodes for anion-exchange membrane fuel cells (AEMFCs). In the experiments, four metal catalysts (nano-grade Pt, PtRu, PdNi and Ag), four AEMs (aQAPS-S8, AT-1, X37-50T and X37-50RT) and two alkaline ionomers (aQAPS-S14 and XB-7) were used. They were verified through several technical parameters examination and cell performance comparison for the optimal selection of AMEs. The bimetallic PdNi nanoparticles (PdNi/C) loaded with Vulcan XC-72R carbon black were used as anode electrodes by using the wet impregnation method, and Ag nanoparticles (Ag/C) were used as the catalyst cathode. It was found that the power density and current density of the X37-50RT are higher than the other three membranes. Also, alkaline ionomers of XB-7 had better performance than aQAPS-S14. The efficiency was improved by 32%, 155% and 27%, respectively, when compared to other membranes by using the same catalyst of PdNi/C, Ag/C and Pt/C. The results are consistent with the membrane ion conductivity measurements, which showed that the conductivity of the X37-50RT membrane is the highest among them. The conductivity values for hydroxide ions (OH⁻) and bromide ions (Br⁻) are 131 mS/cm and 91 mS/cm, respectively. These findings suggest that the properties (water uptake, swelling rate and mechanical) of the anion-exchange membrane (AEM) can serve as a key reference for AEM fuel cell applications. Full article

Aqueous phase reforming (APR) is a promising method for producing hydrogen from biomass-derived feedstocks. In this study, carbon-supported Pt catalysts containing particles of different sizes (below 3 nm) were deposited on different commercially available carbons (i.e., Vulcan XC72 and Ketjenblack EC-600JD) using the metal vapor synthesis approach, and their catalytic efficiency and stability were evaluated in the aqueous phase reforming of ethylene glycol, the simplest polyol containing both C–C and C–O bonds. High-surface-area carbon supports were found to stabilize Pt nanoparticles with a mean diameter of 1.5 nm, preventing metal sintering. In contrast, Pt single atoms and clusters (below 0.5 nm) were not stable under the reaction conditions, contributing minimally to catalytic activity and promoting particle growth. The most effective catalyst Pt_A/C^K, containing a mean Pt NP size of 1.5 nm and highly dispersed on Ketjenblack carbon, demonstrated high hydrogen site time yield (8.92 min⁻¹ at 220 °C) and high stability under both high-temperature treatment conditions and over several recycling runs. The catalyst was also successfully applied to the APR of polyethylene terephthalate (PET), showing potential for hydrogen production from plastic waste. Full article

This research focuses on the rational design of porous enzymatic electrodes, using horseradish peroxidase (HRP) as a model biocatalyst. Our goal was to identify the main obstacles to maximizing biocatalyst utilization within complex porous structures and to assess the impact of various carbon nanomaterials on electrode performance. We evaluated as-synthesized carbon nanomaterials, such as Carbon Aerogel, Coral Carbon, and Carbon Hollow Spheres, against the commercially available Vulcan XC72 carbon nanomaterial. The 3D electrodes were constructed using gelatin as a binder, which was cross-linked with glutaraldehyde. The bioelectrodes were characterized electrochemically in the absence and presence of 3 mM of hydrogen peroxide. The capacitive behavior observed was in accordance with the BET surface area of the materials under study. The catalytic activity towards hydrogen peroxide reduction was partially linked to the capacitive behavior trend in the absence of hydrogen peroxide. Notably, the Coral Carbon electrode demonstrated large capacitive currents but low catalytic currents, an exception to the observed trend. Microscopic analysis of the electrodes indicated suboptimal gelatin distribution in the Coral Carbon electrode. This study also highlighted the challenges in transferring the preparation procedure from one carbon nanomaterial to another, emphasizing the importance of binder quantity, which appears to depend on particle size and quantity and warrants further studies. Under conditions of the present study, Vulcan XC72 with a catalytic current of ca. 300 µA cm⁻² in the presence of 3 mM of hydrogen peroxide was found to be the most optimal biocatalyst support. Full article

This work reports the influence of a reduced graphene oxide (rGO) support on the catalytic performance of Cu@PtRu/rGO electrocatalysts toward methanol oxidation in an acidic medium. These electrocatalysts are synthesized via a two-step reduction method; the first step utilizes ethylene glycol for the reduction of Cu²⁺ ions, forming Cu/rGO. In the second step, spontaneous redox reactions take place, in a process known as galvanic displacement, where the Pt²⁺ and Ru³⁺ species are reduced to form PtRu layers, and the copper is partially oxidized to the solution. Then, the Cu@PtRu/rGO core–shell is produced, comprising Cu in the inner structure (core) and PtRu on the outer part (shell). To compare the catalytic performance of the prepared nanocatalysts (NCs), Pt/C, PtRu/C, and Cu@PtRu/C are also synthesized on Vulcan XC-72R carbon. All catalysts are characterized via X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Cyclic voltammetry (CV) and chronoamperometry (CA) are employed to measure the electrochemical performance. The core–shell/rGO combination is superior in catalytic activity to the traditional Pt/C, PtRu/C, and Cu@PtRu/C catalysts for the methanol oxidation reaction. These results suggest that Cu@PtRu/rGO exhibits a high bulk activity for methanol electrooxidation, a high stability, and a high tolerance to CO poisoning, meaning it is possible to reduce the platinum loading in proton-exchange membrane fuel cells (PEMFCs). Full article

The through-plane gas permeability and morphology of PEFC gas diffusion media (GDM) is investigated for different microporous layer (MPL) ink homogenisation techniques (bath sonication and magnetic stirring) for low- (Vulcan XC-72R) and high (Ketjenblack EC-300J)-surface-area carbon powders. The MPL composition is held constant at 80 wt.% carbon powder and 20 wt.% PTFE for a carbon loading of 1.0 mg cm⁻². The MPL ink homogenisation time is held constant at two hours for both techniques and increased by one hour for bath sonication to compare with previous investigations. The results show that the through-plane gas permeability of the GDM is approximately doubled using magnetic stirring when compared with bath sonication for MPLs composed of Vulcan XC-72R, with a negligible change in surface morphology between the structures produced from either homogenisation technique. The variation in through-plane gas permeability is almost negligible for MPLs composed of Ketjenblack EC-300J compared with Vulcan XC-72R; however, MPL surface morphology changes considerably with bath sonication, producing smoother, less cracked surfaces compared to the large cracks produced via magnetic stirring for a large-surface-area carbon powder. An MPL ink sonication time of three hours results in a percentage reduction in through-plane gas permeability from the GDL substrate permeability by ~72% for Ketjenblack EC-300J compared to ~47% for two hours. Full article

The present work reports the synthesis and the physicochemical characterization of biochar from the organic wastes of nopal (Opuntia Leucotricha), coffee grounds (Coffea arabica) and Ataulfo mango seeds (Mangifera indica) as alternative electrocatalyst supports to Vulcan XC-72 carbon black. The biochars were prepared using pyrolysis from organic wastes collected at three temperatures, 600, 750 and 900 °C, under two atmospheres, N₂ and H₂. The synthesized biochars were characterized using Raman spectroscopy and scanning electron microscopy (SEM) to obtain insights into their chemical structure and morphological nature, respectively, as a function of temperature and pyrolysis atmosphere. A N₂ adsorption/desorption technique, two-point conductivity measurements and cyclic voltammetry (CV) were conducted to evaluate the specific surface area (SSA), electrical conductivity and double-layer capacitance, respectively, of all the biochars to estimate their physical properties as a possible alternative carbon support. The results indicated that the mango biochar demonstrated the highest properties among all the biochars, such as an electrical conductivity of 8.3 S/cm⁻¹ at 900 °C in N₂, a specific surface area of 829 m²/g at 600 °C in H₂ and a capacitance of ~300 mF/g at 900 °C in N₂. The nopal and coffee biochars exhibited excellent specific surface areas, up to 767 m²/g at 600 °C in N₂ and 699 m²/g at 750 °C in H₂, respectively; nonetheless, their electrical conductivity and capacitance were limited. Therefore, the mango biochar at 900 °C in N₂ was considered a suitable alternative carbon material for electrocatalyst support. Additionally, it was possible to determine that the electrical conductivity and capacitance increased as a function of the pyrolysis temperature, while the specific surface area decreased for some biochars as the pyrolysis temperature increased. Overall, it is possible to conclude that heat treatment at a high temperature of 900 °C enhanced the biochar properties toward electrocatalyst support applications. Full article

The adsorption of phenol (Ph), 4-chlorophenol (CP), and 4-cresol (MP) from aqueous solutions on three carbonaceous materials of diverse origins but similar specific surface areas was investigated. Vulcan XC72 carbon black (CB), AKP-5 activated coke (AC), and activated tire pyrolysis char (AP) were examined as adsorbents. The kinetics and equilibrium adsorption, as well as the influence of pH and ionic strength of each solution on the adsorption process, were studied. The results revealed that the adsorption was pH-dependent and preferred an acidic environment. The presence of an inorganic salt in the solution (ionic strength) did not affect the adsorption processes of the three adsorbates. The pseudo-first- and pseudo-second-order equations, as well as the Weber–Morris and Boyd kinetic models, were used to describe the adsorption kinetics. It was found that equilibrium was reached for all adsorbates after approximately 2–3 h. Adsorption kinetics followed a pseudo-second-order model, and the adsorption rate was determined by film diffusion. The adsorption isotherms were described using the Langmuir and Freundlich equations. The results revealed that the adsorption processes of Ph, CP, and MP on all three adsorbents from the water were better described by the Langmuir model. The adsorption of CP was the most efficient, the adsorption of MP was slightly weaker, and the adsorption of phenol was the least efficient. Full article