Search Results (52)

The electrooxidation (EO) of three important environmental contaminants, anticorrosive 1H-benzotriazole (BTA), plasticizer dibutyl phthalate (DBP), and non-ionic surfactant Triton X-100 (tert-octylphenoxy[poly(ethoxy)] ethanol, t-OPPE), was studied as a possible means to improve their elimination from wastewaters, which are an important emission source. EO was performed in a batch reactor with a boron-doped diamond (BDD) anode and a stainless steel cathode. Different supporting electrolytes were tested: NaCl, H₂SO₄, and Na₂SO₄. Results were analysed from the point of their efficacy in terms of degradation rate, kinetics, energy consumption, and transformation products. The highest degradation rate, shortest half-life, and lowest energy consumption was observed in the electrolyte H₂SO₄, followed by Na₂SO₄ with only slightly less favourable characteristics. In both cases, degradation was probably due to the formation of persulphate or sulphate radicals. Transformation products (TPs) were studied mainly in the sulphate media and several oxidation products were identified with all three contaminants, while some evidence of progressive degradation, e.g., ring-opening products, was observed only with t-OPPE. The possible reasons for the lack of further degradation in BTA and DBP are too short of an EO treatment time and perhaps a lack of detection due to unsuitable analytical methods for more polar TPs. Results demonstrate that BDD-based EO is a robust method for the efficient removal of structurally diverse organic contaminants, making it a promising candidate for advanced water treatment technologies. Full article

A CuNiCe-O nanocomposite was fabricated on the Cu₄₀Ni₂₀Al₁₀Ce₂₆Pt₃Ru₁ metallic glass (MG) ribbon surface by dealloying. The influences of Ni and dealloying time on the morphology and EOR performance were analyzed. The results suggest that the catalytic activity and stability of the dealloyed MG ribbon could be significantly enhanced owing to the alloying of Ni to the Cu₆₀Al₁₀Ce₂₆Pt₃Ru₁ MG ribbon precursor. The activated D-Cu₄₀Ni₂₀Al₁₀Ce₂₆Pt₃Ru₁ ribbon obtained at an etching time of 3 h had a better electrochemical ethanol oxidation reaction (EOR) performance than other dealloyed samples due to the formation of abundant active sites and the presence of defects within the CuNiCe-O composite. Full article

This work investigates the relationship between the mean diameter of palladium (Pd) nanoparticles and their surface energy, specifically in the context of alkaline ethanol electro-oxidation for fuel cell applications. Employing a recent generalization of the classical Laviron equation, we derive crucial parameters such as surface energy (σ), adsorption–desorption equilibrium constant (K_eq), and electron transfer coefficient (α) from linear voltammograms obtained from Pd-based nanoparticles supported on Vulcan carbon. Synthesized using two distinct methods, these nanocatalysts exhibit mean diameters ranging from 10 to 41 nm. Our results indicate that the surface energy of the Pd/C nanocatalysts spans σ ~ 0.5–2.5 J/m², showing a linear correlation with particle size while remaining independent of ethanol bulk concentration. The adsorption–desorption equilibrium constant varies with nanoparticle size (~0.1–6 × 10⁻⁶ mol⁻¹) but is unaffected by ethanol concentration. Significantly, we identify an optimal mean diameter of approximately 28 nm for enhanced electrocatalytic activity, revealing critical size-dependent effects on catalytic efficiency. This research contributes to the ongoing development of cost-effective and durable fuel cell components by optimizing nanoparticle characteristics, thus advancing the performance of Pd-based catalysts in practical applications. Our findings are essential for the continued evolution of nanomaterials in fuel cell technologies, particularly in improving efficiency and reducing reliance on critical raw materials. Full article

By controlling the structure and composition of Pt-based nanoalloys, the ethanol oxidation reaction (EOR) performances of Pt alloy catalysts can be effectively improved. Herein, we successfully synthesis sub-10 nm PdNi@PtNi nanoparticles (PdNi@PtNi NPs) with a core–shell structure by a one-pot method. The sub 10 nm core–shell nanoparticles possess more effective atoms and exhibit a synergistic effect which can lead to a shift in the d-band center and alter binding energies toward adsorbates. Due to the synergistic effect and unique core–shell structure, the PdNi@PtNi NP catalysts exhibit excellent electrocatalytic performance for ethanol oxidation reactions in alkaline, achieving 9.30 times more mass activity and 7.05 times more specific activity that of the state-of-the-art Pt/C catalysts. Moreover, the stability of PdNi@PtNi NPs was also greatly improved over PtNi nanoparticles, PtPd nanoparticles, and commercial Pt/C. This strategy provides a new idea for improving the electrocatalytic performance of Pt-based catalysts for EORs. Full article

Waste valorization is necessary in today’s society to achieve a sustainable economy and prosperity. In this work, a novel approach to the waste valorization of cuttlebone was investigated. This material was ground and calcined at 900 °C for 5 h in an inert atmosphere. The resulting calcined cuttlebone (CCB) was characterized using XRD, SEM, FTIR, BET, TGA, Zetasizer, and potential methods. The main phases in the CCB were determined to be CaO, MgO, Ca₃(PO₄)₂, and residual carbon. CCB was investigated as an adsorbent for the removal of dye from simulated wastewater streams. The maximum adsorption capacities for rhodamine B and crystal violet dyes were estimated to be 519 and 921 mg/g, respectively. For both dyes, the Avrami model was the best-fit model for representing adsorption kinetics. The study of adsorbent regeneration for CV as a representative example involved the use of several chemical solvents. Ethanol solvent was shown to have the highest adsorbent regeneration method efficiency, reaching 65.20%. In addition, CCB was investigated for methanol electro-oxidation for energy generation. As the methanol concentration increased, the maximum current density produced by the CCB increased, reaching approximately 50 mA/cm². This work paves the way toward waste valorization of natural matter for sustainable production and consumption of material, as per the requirements of the circular economy principles. Full article

The production of H₂ from renewable sources represents a crucial challenge for the planet’s future to achieve net zero emissions and store renewable energy. A possible alternative to water electrolysis (WE), which requires high potential (E > 1.48 V) to trigger the oxygen evolution reaction (OER), would be alcohol electrochemical reforming (ER), which implies the oxidation of short organic molecules such as methanol or ethanol. In ER, energy must be supplied to the system, but from a thermodynamic point of view, the energy request for the methanol or ethanol oxidation reaction is much lower than that of the OER. To study this process, an in-house 50 wt.% Pt₁Ru₁/C anodic catalyst was easily synthesized according to the Pt sulphite complex route and the impregnation of a carbon support (Ketjenblack, KB) and a Ru precursor. X-ray diffraction (XRD), X-ray fluorescence (XRF) spectroscopy, and Transmission Electron Microscopy (TEM) were used to characterize the structure, composition, and morphology of the catalyst. It appears that two distinct crystallographic phases of the Pt and Ru nanoparticles were encountered after the synthesis conducted by Ru impregnation. For the electrochemical measurements, ethanol electrooxidation (2 M CH₃CH₂OH) was studied first in a half cell with a rotating disc electrode (RDE) configuration under acid conditions and then in a direct ethanol electroreforming (or electrolysis) cell, equipped with a proton exchange membrane (PEM) as the electrolyte. The output current density was 0.93 A cm⁻² at 1 V and 90 °C in 2 M ethanol. The remarkable current densities obtained in the alcohol electrolyzer at a low voltage are better than the actual state of the art for PEM ethanol ER. Full article

This work reports the use of cellulose as a template to prepare nanosized WO₃ or NiWO₄ and its application as a co-catalyst in the electro-oxidation of ethanol and glycerol. Microcrystalline cellulose was hydrolyzed with phosphotungstic acid (H₃PW₁₂O₄₀) to prepare the nanocrystalline cellulose template. The latter was air-calcinated to remove the template and obtain nanometric WO₃. Tungsten oxide was impregnated with Ni(NO₃)₂, which was subsequently air-calcinated to obtain the nanometric NiWO₄. Elemental analysis confirmed the coexistence of nickel and tungsten, whereas thermal analysis evidenced a high thermal stability for these materials. The X-ray diffractograms displayed crystal facets of WO₃ and, when Ni(II) was added, NiWO₄. The transmission electron micrographs corroborated the formation of nanosized particles with average particle sizes in the range of 30 to 50 nm. Finally, to apply this material, Pt/WO₃-C and Pt/WO₃-NiWO₄-C were prepared and used in ethanol and glycerol electro-oxidation in an alkaline medium, observing a promotional effect of the oxide and tungstate by reducing the onset potential and increasing the current density. These materials show great potential to produce clean electricity or green hydrogen, contributing to energetic transition. Full article

Currently, great importance has been assigned to designing cutting-edge materials for oxygen and hydrogen generation from hybrid water electrolysis as an ideal fuel alternative in energy-conversion devices. This work reports on the electrochemical organic molecule oxidation in alkaline media, intending to promote water electrolysis at early onset potential with more current densities using Sn-Cu oxidized heterostructures. The electrocatalysts were easily and rapidly synthesized by the microwave-heated synthesis process in the presence of a small quantity of ethylene glycol. The X-ray diffraction and Field Emission Scanning Electron Microscopy analyses confirm the presence of CuO and SnO₂ phases, which significantly improves the electrochemical activity of the composite toward the Oxygen Evolution Reaction (OER) in alkaline media in the presence of 1.0 mol L⁻¹ ethanol, yielding 8.0 mA cm⁻² at 1.6 V. The charge transfer resistance (R_ct) was determined using electrochemical impedance spectroscopy, and the result shows that the R_ct of SnO₂/CuO drastically decreased. The findings in this work highlight that the designed oxidized heterostructures with non-noble metals are promising candidates for energy conversion devices and sensors. Furthermore, this work confirms the advantages of using an assisted microwave heating process to develop an advanced SnO₂/CuO composite with the potential to be used in electro-oxidation processes. Full article

In this paper, for the first time, a CoNi₂O₄ nanocatalyst coated on the surface of activated carbon wheat husk (ACWH) was synthesized in the form of CoNi₂O₄/ACWH through a hydrothermal process. The electrocatalytic activity of this catalyst was evaluated using methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) processes for use in anodes of alcohol fuel cells. Adding ACWH, as a cheap carbon biomass with an excellent active surface area, improves the performance of the catalyst in the oxidation of alcohols. The current density of CoNi₂O₄/ACWH in the MOR process is 160 mA/cm² at an optimal methanol concentration of 2 M; this oxidation current density in the EOR process and at a concentration of 1.5 M ethanol is 150 mA/cm². The stability of CoNi₂O₄/ACWH in MOR and EOR processes, after 1000 consecutive CV cycles, is 98.6% and 94.6%, respectively. Full article

Bimetallic Pt₃Eu/C, Pt₃La/C, and Pt₃Ce/C electrocatalysts have been prepared, characterized, and tested for ethanol electro-oxidation (EEO). The materials were synthesized by chemical reduction with NaBH₄, rendering nanosized particles with actual compositions close to the nominals and no alloy formation. X-ray photoelectron spectroscopy (XPS) confirmed that the auxiliary rare-earth metals were present on the surface in oxide form. The electrochemical analyses in acid and alkaline EEO evidenced that, compared to Pt/C, the addition of rare earth metals in the form of oxides reduced the onset potential, increased the current density, and enhanced the stability. The results were fully confirmed in the DEFC single-cell measurements. Finally, the presence of rare earth metals in the oxidized form increased the percentage of acetic acid as the final product, making the electrocatalysts more selective and efficient than Pt/C, where acetaldehyde was the main product. Full article

Direct ethanol fuel cells (DEFCs) need newly designed novel affordable catalysts for commercialization. Additionally, unlike bimetallic systems, trimetallic catalytic systems are not extensively investigated in terms of their catalytic potential toward redox reactions in fuel cells. Furthermore, the Rh potential to break the ethanol rigid C-C bond at low applied potentials, and therefore enhance the DEFC efficiency and CO₂ yield, is controversial amongst researchers. In this work, two PdRhNi/C, Pd/C, Rh/C and Ni/C electrocatalysts are synthesized via a one-step impregnation process at ambient pressure and temperature. The catalysts are then applied for ethanol electrooxidation reaction (EOR). Electrochemical evaluation is performed using cyclic voltammetry (CV) and chronoamperometry (CA). Physiochemical characterization is pursued using X-ray diffraction (XRD), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Unlike Pd/C, the prepared Rh/C and Ni/C do not show any activity for (EOR). The followed protocol produces alloyed dispersed PdRhNi nanoparticles of 3 nm in size. However, the PdRhNi/C samples underperform the monometallic Pd/C, even though the Ni or Rh individual addition to it enhances its activity, as reported in the literature herein. The exact reasons for the low PdRhNi performance are not fully understood. However, a reasonable reference can be given about the lower Pd surface coverage on both PdRhNi samples according to the XPS and EDX results. Furthermore, adding both Rh and Ni to Pd exercises compressive strain on the Pd lattice, noted by the PdRhNi XRD peak shift to higher angles. Full article

Recently, transition metal oxides have been considered for various applications due to their unique properties. We present the synthesis of a three-component catalyst consisting of zirconium oxide (ZrO₂), nickel oxide (NiO), and reduced graphene oxide (rGO) in the form of ZrO₂/NiO/rGO by a simple one-step hydrothermal method. X-ray powder diffraction (XRD), scanning electron microscope (SEM), and bright-field transmission electron microscopy (BF-TEM) analyses were performed to accurately characterize the catalysts. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) analyses were also carried out to investigate the methanol and ethanol alcohol electrooxidation ability of the synthesized nanocatalysts. Inspired by the good potential of metal oxides in the field of catalysts, especially in fuel-cell anodes, we investigated the capability of this catalyst in the methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). After proving the successful synthesis and examining the surface morphology of these materials, detailed electrochemical tests were performed to show the outstanding capability of this new nanocatalyst for use in the anode of alcohol fuel cells. ZrO₂/NiO/rGO indicated a current density of 26.6 mA/cm² at a peak potential of 0.52 V and 99.5% cyclic stability in the MOR and a current density of 17.3 mA/cm² at a peak potential of 0.52 V and 98.5% cyclic stability in the EOR (at optimal concentration/scan rate 20 mV/s), representing an attractive option for use in the anode of alcoholic fuel cells. Full article

Water electrolysis is a thermodynamically energy-intensive process. One approach employed to make water electrolysis kinetically favorable is replacing the oxygen evolution reaction (OER) at the anode by facile electrooxidation of biomass-feedstocks such as ethanol, methanol, glycerol, and lignin due to the presence of readily oxidizable functional groups. In this work, we report a simplistic approach for hydrogen generation by lignin electrolysis, utilizing a low-cost nickel foam as both anode and cathode sandwiched with hydroxide ion (OH^-) exchange membrane in a 3D printed reactor. The performance of the lignin electrolysis was analyzed under various flow rates of anolyte (lignin)/catholyte (KOH) in the anode and cathode chambers. The lignin electrolysis outcompetes traditional water electrolysis by achieving higher current density in the applied voltage range from 0 to 2.5 V at room temperature. The charge transfer resistance for the lignin electrolysis is lower than that of the water electrolysis characterized by impedance spectroscopy. The enhanced current density from the lignin electrolysis at low overvoltage has been presumed from the oxidation of reactive functional groups present in the lignin, facilitating faster electron transfer. Moreover, the hydrogen production rate calculated from the chronoamperometry test of the lignin electrolysis is 2.7 times higher than that of water electrolysis. Thus, the electrochemical oxidation of lignin can potentially lower the capital cost of renewable hydrogen production. Full article

Ethanol is considered an alternative fuel to power fuel cells, especially due to its ease of transport and storage and renewable production on a large scale. However, its use in direct ethanol fuel cells (DEFC) is still limited by incomplete electro-oxidation and slow reaction kinetics. Modeling approaches have focused on investigating different reaction mechanisms, but so far, no formal analysis of model parameter sensitivity has been conducted. This work modeled and identified sensitive parameters for different types of Pt–Sn catalysts previously prepared by our research group that displayed good performance in the 5–15 mW/cm² range (relative to a performance of 12 mW/cm² achieved by a commercial ETEK catalyst). Analyses to study the effect of these parameters on coverage fraction distribution, reaction rates and possible correlations were also performed. The model was developed based on Butler–Volmer kinetics and on a reaction mechanism previously reported in the literature. Statistical developments were considered to compute parameter uncertainties for a non-linear system with non-linear restrictions. The model achieved very good fits to experimental data, with low RMSE values between 0.22 × 10⁻⁴ and 4.2 × 10⁻⁴ A/cm², while also showing surface coverage fraction distributions in agreement with other experiment-based works from the literature. All catalysts taken into account, the most sensitive parameters were the reaction rate constants associated with the formation of adsorbed CH₃CO, and the direct and reverse water dissociative adsorption reactions, respectively. Additional analyses suggested that there is not much correlation between the parameters. The results from this work could contribute to the state-of-the-art DEFC models by providing insights into which variables may be assumed constant or which ones have the greatest impact on the model output, thus helping to reduce the model size and computational time for future broader DEFC models. Full article

We report a systematic study of the electrocatalytic properties and stability of a series of 1–2 nm Au, Pd, and AuPd alloy nanoparticles (NPs) for the ethanol oxidation reaction (EOR). Following EOR electrocatalysis, NP sizes and compositions were characterized using aberration-corrected scanning transmission electron microscopy (ac-STEM) and energy dispersive spectroscopy (EDS). Two main findings emerge from this study. First, alloyed AuPd NPs exhibit enhanced electrocatalytic EOR activity compared to either monometallic Au or Pd NPs. Specifically, NPs having a 3:1 ratio of Au:Pd exhibit an ~8-fold increase in peak current density compared to Pd NPs, with an onset potential shifted ~200 mV more to the negative compared to Au NPs. Second, the size and composition of AuPd alloy NPs do not (within experimental error) change following 1.0 or 2.0 h chronoamperometry experiments, while monometallic Au NPs increase in size from 2 to 5 nm under the same conditions. Notably, this report demonstrates the importance of post-catalytic ac-STEM/EDS characterization for fully evaluating NP activity and stability, especially for 1–2 nm NPs that may change in size or structure during electrocatalysis. Full article