Ethanol Oxidation In Alkaline Media Research Articles

New and Ultra‐Rapid Approach for Electrosynthesis of Highly Efficient Catalysts of Poly(para‐phenylenediamine) Supported Copper Oxide for Ethanol Oxidation in Alkaline Medium

AbstractHerein, a new and simple strategy based on electrochemical cascade reactions was used to prepare copper/poly(para‐phenylenediamine). The catalysts were prepared by a facile one‐pot synthesis via an electrochemical method in a solution containing monomer and copper in a suitable concentration using potentiostatic or galvanostatic mode. Using galvanostatic mode leads to the formation of nanodendritic shape of copper hydroxide‐copper oxide in contrast with potentiostatic mode which leads to a spherical form. The response toward ethanol oxidation was greatly affected by the morphology of the obtained nanocomposite. Indeed, the current density obtained when using potentiostatic mode is about 26.55 mA cm−2 at 1.05 V vs Ag/AgCl. This performance is about 2.4 times higher than of the electrocatalyst prepared by galvanostatic mode (11.09 mA cm−2 at 0.85 V). The durability and long‐term stability of the obtained electrocatalysts were investigated using chronoamperometry and cyclic voltammetry. The decrease in current density is about 19 % and 49 % for electrocatalysts prepared by galvanostatic and potentiostatic mode respectively, after 700 scans. Finally, ex–situ FTIR spectroscopy was conducted in order to understand the reaction mechanism of ethanol oxidation in alkaline medium. It demonstrates that Cu(OH)2−Cu2O@PpPD can perform the complete oxidation of ethanol molecules, leading to the formation of CO2 molecule as the final product. This study highlighted a new simple and facile approach for synthesizing electrocatalysts based on Cu(OH)2−Cu2O@PpPD for alcohol oxidation applications.

Investigation of the Dependence of Electrocatalytic Activity of Copper and Palladium Nanoparticles on Morphology and Shape Formation

A synthesis strategy for the manufacture of inexpensive highly efficient nanostructured catalysts has been developed. The developed unique nonplatinoid copper-based catalysts with different surface morphology were investigated as a functional layer with high activity in the ethanol oxidation in alkaline media. A modifying layer with controlled morphology, composition, and excellent electrocatalytic activity was synthesized by electrochemical deposition by varying such synthesis parameters as deposition temperature and time, concentration of structure-forming additives, and electrodeposition current. The dependence of the samples’ electrocatalytic activity on the shaping factors was established. According to the electrochemical study results, the highest current density peak of up to 33.01 mA cm−2, and hence the highest catalytic activity in comparison to other samples, were possessed by a catalyst with a regular cubic particle shape. A catalyst consisting of plate-like nanoparticles with a certain percentage of disclinations had similar, but slightly less activity, with a current density peak of up to 31.59 mA cm−2. The samples’ activity values are 8 times higher for cubic particles and 7.5 times higher for particles with a triangular plate shape than for an unmodified smooth copper film. The developed samples can be considered as quite competitive to platinoid catalysts, which significantly outperform copper analogues.

Stabilizing agents assisted construction of monometallic self-supporting Palladium NCs with ultrafine nanostructures and rich surface area for highly efficient direct ethanol fuel cell

Design and construct nanoparticles to develop highly efficient electrocatalysts for energy-associated fuel cells remains a significant challenge. High cost, slow reaction kinetics, and poor durability of catalysts are also essential challenges toward the commercialization of DEFCs. Hence, the optimizationof highly structuredPalladium nanocatalysts (Pd-NCs) with suitable nanostructure, rich surface area, and excellent electrochemical performance is a hot area to explore. Herein, we have successfully developed monometallic Pd-NCs with different nanostructures (nonporous, nanoshere, cubes, and unspecified shapes) via altering the varieties of stabilizing agents (PVA, PVP, AA, CTAB, and SOA) for direct ethanol fuel cells (DEFCs) in alkaline medium. The morphological characterization findings indicate that the monometallic Pd-NCs have ultrafine morphologies with small particle size and large surface areas, indicating the role of stabilizing agents in regulating structures. The obtained CTAB-Pd NCs exhibited promising electrocatalytic activity (5429 mAmgPd-1) toward ethanol oxidation in alkaline medium, which is outperforms SF-Pd NCs (917 mAmgPd-1), PVA-Pd NCs (3458 mAmgPd-1), PVP-Pd NCs (3678 mAmgPd-1), AA-Pd NCs (5126 mAmgPd-1), and SOA-Pd NCs (2196 mAmgPd-1). More impressively, the as-prepared CTAB-Pd NCs demonstrated greater EOR durability and a strong ability to remove CO poisoning to accelerate the overall DEFC system. Therefore, our prepared catalysts represents outstanding EOR performance than most of resent reported catalysts, due to their distinct structures and huge ECSA. This work provides more insight into the structure-regulated nanocatalysts, which will contribute to the rational development of highly-efficient Pd-based electrocatalysts for practical application of DEFCs.

Pd, Ag and Bi carbon-supported electrocatalysts as electrochemical multifunctional materials for ethanol oxidation and dopamine determination

This manuscript describes the investigation towards the multifunctional synthesis, characterization, and application of different Pd, Ag and Bi-carbon black supported electrocatalysts in two different fields in electrochemistry: fuel cells and electrochemical sensors. Throughout morphological and electrochemical characterizations, comprising scanning and transmission electron microscopies, X-ray powder diffraction, electrochemical impedance spectroscopy, and cyclic voltammetry techniques, the materials were characterized to better understand their properties towards proposed applications. Afterward, the materials were employed for ethanol oxidation in alkaline media, with investigations by chronoamperometry, cyclic voltammetry, and by closing a direct alkaline fuel cell, which the Pd50Ag45Bi05/C composite presented attractive ethanol catalysis behavior, with a maximum power density of 19.70 mW cm−2, at 30.59 mA cm−2. Also, the proposed device was applied for dopamine determination by square wave voltammetry. In this sense, two linear behaviors, respectively ranging from 0.2 to 1.0 and 4.0 to 40 μmol L−1 were obtained, due to two distinctive mechanisms. This higher activity has been attributed to the synergism among the used metals and proportions contributing to the bifunctional and electronic effects. As synthetic samples investigations were accomplished, data reinforces the proposed material as a possible interfacing composite in electrochemistry.

Influence of the composition and morphology of PdNiFe/C nanocatalysts toward ethanol oxidation

We investigate the electrocatalytic activity of Pd, NiFe@Pd, and PdxNiyFez catalysts toward ethanol oxidation in alkaline media using electrochemical and spectroelectrochemical measurements. The addition of Ni-Fe to Pd (both alloy and core–shell) enhances their activity and stability toward ethanol oxidation, mainly for those with 30at.% of Ni + Fe. In situ FTIR data reveals that Ni and Fe favor the formation of acetate and acetic acid at lower potentials due to their oxophilic character, while the core–shell catalyst produces these intermediates at the lowest potentials. Our study highlights the synergetic role of composition and core–shell morphology in their catalytic activity.

Pd Monolayer on the 3D-Hollow-Porous Au Microsphere as an Advanced Electrocatalyst for the Ethanol Oxidation Reaction

Pd is a highly active non-Pt anode in direct ethanol fuel cells, and its morphology and structural composition heavily influence its electrocatalytic efficiency. In this study, three-dimensional (3D)-hollow Au microspheres (HNPs-Au) as a support for the Pd monolayer (HNPs-Au@Pd) were synthesized using a simple template method and galvanic replacement reaction. The experimental results and theoretical calculations show that the presence of HNPs-Au enhances the catalytic activity of ethanol oxidation in alkaline media, improving the electroactivity of metallic Pd. Benefiting from the 3D-hollow-porous structure and the significant synergistic impact between Au and Pd (balancing the adsorption energy of the intermediate and reactant molecules), HNPs-Au@Pd achieves a 10.8-fold mass activity and a 3.3-fold enhancement of the specific activity for the ethanol oxidation reaction when compared to commercial Pd/C. The present work not only enriches the preparation strategy of porous metal materials but also opens up a sector for the construction of anodic electrocatalysts with a wide range of applications.

Designing New Material Based on Functionalized Multi-Walled Carbon Nanotubes and Cu(OH)2-Cu2O/Polypyrrole Catalyst for Ethanol Oxidation in Alkaline Medium.

In this work, copper(II) hydroxide (Cu(OH)2) and copper oxide (Cu2O) nanostructures are deposited on functionalized multi-walled carbon nanotubes/polypyrrole to report an efficient electrocatalyst for ethanol oxidation in alkaline medium. In the first step, the deposition of functionalized multi-walled nanotubes of carbon (F-MWCNTs) on the electrode surface was carried out using drop casting mode followed by the electrodeposition of polypyrrole (PPy) and copper nanoparticles (Cu-Nps) using galvanostatic mode. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed in order to study the morphology and the structure of the elaborated catalysts. Electrochemical characterization conducted by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed that the introduction of functionalized multi-walled carbon nanotubes enhances the electric properties of the nanocomposites and offers a large active surface area. The prepared electrocatalyst was then tested in a solution of 0.1 M NaOH containing 0.2 M of ethanol showing high performance (7 mA cm−2 at 0.85 V vs Ag/AgCl) and good stability (over 1800 s) toward ethanol oxidation.

Construction of Co3O4-Ni3S4-rGO ternary hybrid as an efficient nanoelectrocatalyst for methanol and ethanol oxidation in alkaline media

In this study, a three-component nanocatalyst consisting of cobalt oxide (Co3O4), nickel sulfide (Ni3S4), and reduced graphene oxide (rGO) is synthesized by the hydrothermal method. Physical characterization confirmed the successful synthesis of these nanocatalysts. In this study, Co3O4- Ni3S4 (CN) and Co3O4- Ni3S4 -rGO (CNR) is reported for application in alcohol fuel cells for the first time. Electrochemical investigations show that both nanocatalysts have relatively good efficiencies in the methanol and ethanol electrooxidation process. Adding rGO to the CN structure causes the nanocatalyst to gain a higher specific surface area and increase its electrical conductivity. CNR showed 96% stability in the methanol oxidation reaction (MOR) process and 94% stability in the ethanol oxidation reaction (EOR) process. The electron transfer kinetics are investigated in the MOR and EOR processes. CNR indicates the exchange current of 8.61 × 10−7 mA/cm2 in MOR and 1.87 × 10−7 mA/cm2 in EOR that is higher than the exchange current of CN, which proves a clear reason for the excellent effect of adding rGO to the nanocatalyst. In this work, the synergistic effect of Co3O4 as metal oxide and Ni3S4 as metal sulfide, and rGO as a conductive substrate is investigated. Finally, CN and CNR nanocatalysts introduce as stable and inexpensive catalysts in MOR and EOR processes for use in alcoholic fuel cells.

Multicomponent nanoporous Al–Ni–Cu–Pt–Pd–Co as highly stable anode catalysts in a flexible room-temperature pure ethanol–powered solid-state fuel cell

Developing highly active and durable anodic catalysts with low noble-metal content for ethanol electrooxidation is important for boosting the performance of direct room-temperature ethanol fuel cells. Herein, we use a general and scalable dealloying method to prepare a series of nanoporous multicomponent alloys with different alloy compositions. It is found that the subsurface alloy composition play an important role on the catalytic activity of the surface noble metals due to the surface strain and electronic effect. By screening, we find that the AlNiCuPtPdCo senary combination exhibits the highest electrocatalytic activity for ethanol oxidation in alkaline media. On the cathode electrode, a highly ORR active, durable, and ethanol-tolerant Co@N–C catalyst derived from MOF is used. Impressively, the designed solid-state room-temperature ethanol fuel cell using such anodic and cathodic catalysts can work immediately with the addition of pure ethanol, delivering a high power density of ~9.20 mW cm−2 with 1 mL ethanol. The flexible fuel cell can also work repeatedly when the added ethanol is consumed.

Simultaneous hydrogen evolution and ethanol oxidation in alkaline medium via a self-supported bifunctional electrocatalyst of Ni-Fe phosphide/Ni foam

Hydrogen (H2) generated via water electrolysis exhibits great potential in addressing the urgent environmental and energy issues. Nevertheless, this approach is immensely handicapped by the tardy oxygen evolution reaction (OER). The ethanol oxidation reaction (EOR) can feasibly substitute the OER for hydrogen generation with less power expending on account of the more beneficial thermodynamics and kinetics. Herein, the hierarchical nickel–iron phosphide (Ni-Fe-P) nanosheet directly grown on Ni foam (NF) is proposed as a high-efficiency self-supported bifunctional electrocatalyst. Integrating the advantages of the unique architecture and the composition, the Ni-Fe-P/NF electrode displays highly alluring electrocatalytic activity and stability toward EOR as well as hydrogen evolution reaction (HER). The as-assembled Ni-Fe-P/NF//Ni-Fe-P/NF hybrid ethanol–water electrolyser only requires 1.53 V to supply 10 mA cm−2, outperforming the sole water splitting (1.66 V). Noteworthily, the liquid product of electrolysis is more meritorious than the raw material, highlighting that the hybrid ethanol–water electrolyser we elaborated possesses prodigious potentiality for application in energy-saving H2 generation and the oxidation of ethanol into acetic acid. This work may provide an innovative strategy in designing and developing other high-efficiency organic molecule electrocatalysts and related energy-saving H2 production applications in the future.

Effect of CeO2 Presence on the Electronic Structure and the Activity for Ethanol Oxidation of Carbon Supported Pt

Pt/CeO2/C electrocatalysts in different compositions were prepared and their structural characteristics and activities for ethanol oxidation in alkaline media were evaluated. In the presence of CeO2, an increase in the platinum particle size was observed. XANES measurements indicated that the Pt d-band vacancies increased with increasing CeO2 amounts. For the first time, the decrease in electro activity was described to an electronic effect for high CeO2 contents. The dependence of the activity for ethanol oxidation on CeO2 content went to a maximum, due to the counteracting bifunctional and electronic effects of the metal oxide.

Effect of electrochemical activation on the performance and stability of hybrid (PPy/Cu2O nanodendrites) for efficient ethanol oxidation in alkaline medium

Abstract One of the most challenges in Direct Ethanol Fuel Cell (DEFC) is to prevent the poisoning of the surface of the electrode due to the slow kinetics of ethanol oxidation reaction. Herein, we report the development of a new catalysts for ethanol oxidation using a well-defined Cu2O nanodendrites (Cu2O-NDs) supported on polypyrrole film (PPy) using a simple electrochemical approach. The effect of regeneration of the electrocatalyst in acidic medium on the performance of ethanol electro-oxidation was reported for the first time. Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) were used to characterize the new catalysts. The SEM and TEM images confirm that the octahedral shape of Copper oxide is converted to a dendritic one after the regeneration of the catalyst. The electrochemical behavior of the prepared catalysts towards the oxidation of ethanol were investigated by Cyclic voltammetry (CV), Chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The current obtained by CV measurements on Cu2O-NDs/PPy/CPE was about 4 mA cm−2 which is 1.77 time higher than Cu2O/PPy/CPE catalyst (2.25 mA cm−2) with a shift of 60 mV and 150 mV in anodic and onset potential respectively demonstrating a good catalytic performance for ethanol oxidation. The stability test shows that the Cu2O-NDs/PPy/CPE loses only 7.25% of its initial current after 1000 cycles. Finally, Ex–situ FTIR spectroscopy was conducted in order to understand the reaction mechanism. Interestingly, our ex-situ FTIR results demonstrated that the ethanol oxidation mechanism displayed shape dependent behavior of copper oxide, indicating that the ethanol molecules are totally oxidized on the Cu2O-NDs leading to the formation of CO2 molecule as final product.

Development of palladium catalysts modified by ruthenium and molybdenum as anode in direct ethanol fuel cell

Physical and electrochemical properties of Pd catalysts combined with Ru and Mo on carbon support were investigated. To this end, Pd, Pd1.3Ru1.0, Pd3.2Ru1.3Mo1.0 and Pd1.5Ru0.8Mo1.0 were synthesized on Carbon Vulcan XC72 support by the method of thermal decomposition of polymeric precursors and then physically and electrochemically characterized. The highest reaction yields are obtained for Pd3.2Ru1.3Mo1.0/C and Pd1.5Ru0.8Mo1.0/C and, as demonstrated by thermal analysis, they also show the smallest metal/carbon ratio compared the other catalysts. XRD (X-ray Diffraction) and Raman analyses show the presence of PdO and RuO2 for the Pd/C and the Pd1.3Ru1.0/C catalysts, respectively, a fact not observed for the Pd3.2Ru1.3 Mo1.0 /C and the Pd1.5Ru0.8Mo1.0/C catalysts. The catalytic activities were tested for the ethanol oxidation in alkaline medium. Cyclic voltammetry (CV) shows Pd1.3Ru1.0/C exhibiting the highest peak of current density, followed by Pd3.2Ru1.3Mo1.0/C, Pd1.5Ru0.8Mo1.0/C and Pd/C. From, chronoamperometry (CA), it is possible to observe the lowest rate of poisoning for the Pd1.3Ru1.0/C, followed by Pd3.2Ru1.3Mo1.0/C, Pd1.5Ru0.8Mo1.0/C and Pd/C. These results suggested that catalytic activity of the binary and the ternary catalysts are improved in comparison with Pd/C. The presence of RuO2 activated the bifunctional mechanism and improved the catalytic activity in the Pd1.3Ru1.0/C catalyst. The addition of Mo in the catalysts enhanced the catalytic activity by the intrinsic mechanism, suggesting a synergistic effect between metals. In summary, we suggest that it is possible to synthesize ternary PdRuMo catalysts supported on Carbon Vulcan XC72, resulting in materials with lower poisoning rates and lower costs than Pd/C.Graphic abstract

Easy approach for decorating of poly 4-aminithiophenol with Pd nanoparticles: an efficient electrocatalyst for ethanol oxidation in alkaline media

In this work, a polymer composite based on poly 4-aminothiophenol (p-ATP) is prepared via a facile electrochemical route and is used as an appropriate support for Pd nanoparticles. The morphological studies reveal that a nanofiber structure patterned on the multiwalled carbon nanotubes (MWCNT) structure is obtained for the synthesized catalyst viz. Pd/p-ATP/MWCNT. The Pd/p-ATP/MWCNT catalyst delivers a mass activity of 3245 $$ \mathrm{mA}\ {\mathrm{mg}}_{\mathrm{Pd}}^{-1} $$ manifesting its superb electrocatalytic activity for ethanol oxidation in the alkaline media. The vital role of the polymeric substrate on the electrocatalytic activity of Pd nanoparticles is established by comparing the catalytic performance of Pd/p-ATP/MWCNT with Pd/MWCNT. Finally, the superb activity of the synthesized catalyst is explicated according to the mechanism of ethanol oxidation on the synthesized catalyst.

Pd coated one-dimensional Ag nanostructures: Controllable architecture and their electrocatalytic performance for ethanol oxidation in alkaline media

One-dimensional (1D) metal-coated Pd structures are efficient catalysts for the ethanol electro-oxidation and promising strategy for minimizing the Pd-loading toward commercialization of direct ethanol fuel cells (DEFCs). Herein, the decorated and core-shell architectures of a novel Pd coating on Ag nanowires (PdAg-NWs) are controllable by a two-step polyol method based on the galvanic replacement reaction. The integration of uniform shell with a low Pd concentration and partial hollow structure onto 1D PdAg-NWs exhibits the highest efficiency for ethanol oxidation reaction (EOR) in alkaline solution. In comparison with Pd nanoparticles (PdNPs/C), the PdAgNWs/C performes 11 times superior EOR activity, and the onset potential shifts 80 mV negatively. The presence of Ag in PdAg-NWs enhances the absorption capacity of ethanol molecules and hydroxyl ions on the active sites, and improves the catalyst tolerance to CO-like intermediates, making them a potential anodic catalyst for DEFCs.

Attractive nanofiber structure based on Cu-Ti/metal sandwich film with excellent electrocatalytic performance for ethanol oxidation

The support materials are an important part of catalysts and they are the dispersant, adhesive, and support for other components. In this study, three types of thin films with different structures were used as the precursor to prepare loading Pd catalysts. The one-step dealloying method was used to prepare a semiconductor nanofiber film (NFF) support material with upward directional growth from the substrate. Pd/NFF and Pd/NiO/NFF loaded Pd catalysts were prepared using NFF as the support material, and the electrochemical catalytic properties for ethanol oxidation in alkaline media were studied. Cyclic votammetry showed that the NFF support material effectively inhibited agglomeration of palladium, increased the number of active sites of Pd, and improved the electrocatalytic properties of Pd for ethanol oxidation. In addition, the Pd/NiO/NFF loaded Pd catalyst obtained by modification with nickel oxide significantly improved the electrocatalytic performance for ethanol oxidation compared with the Pd/NFF loaded Pd catalyst. These results show that NiO is conductive to absorption of oxygen-containing groups on the surface of the catalyst and can further improve the electrocatalytic ability of Pd for ethanol oxidation. All of the above results demonstrate that the support material prepared by the dealloying method has application prospects in load-type catalysts.

Boosting ethanol oxidation over nickel oxide through construction of quasi-one-dimensional morphology and hierarchically porous structure

Quasi-one-dimensional NiO with a hierarchically porous structure was synthesized through a facile coordination−precipitation method with the coupling effect of ammonia and a post-calcination treatment. The electrocatalytic properties of NiO fibers for the oxidation of ethanol were compared with those of NiO spheres. The results show that the fibrous NiO possesses a larger specific surface area of 140.153 m2/g and a lower electrical resistivity of 4.5×105 Ω·m, leading to an impressively superior electrocatalytic activity to spherical NiO for ethanol oxidation in alkaline media. The current decay on fibrous NiO at 0.6 V in 100−900 s was 0.00003%, which is much lower than that of spherical NiO, indicating its better stability. The unique morphology and hierarchically porous structure give the fibrous NiO great potential to be used as an anodic electrocatalyst for direct ethanol fuel cells.

Synthesis and testing of cobalt leaf-like nanomaterials as an active catalyst for ethanol oxidation

A simple electrodeposition technique has been used to synthesize Co nanoparticles with a 3D leaf-like morphology at room temperature. The prepared Co material has a layered sheet structure of a few nanometers thickness. The surface area of the Co leaf-like structure is three times higher than that of the Co nanoparticles. The prepared nanoparticles exhibit high activity towards ethanol oxidation in alkaline media with an onset potential of 0 V vs Ag/AgCl, which is one of the lowest reported potentials for a non-precious catalyst. The current density is observed to increase with increasing ethanol concentration from 0.1 M to 2 M, after which it plateaus. Mixing the Co catalyst with Vulcan carbon (20 wt%) resulted in a 50% increase in current discharge at different ethanol concentrations due to the improvement in mass and charge transfer rates as confirmed by EIS measurements. Also, Co deposited in situ on the surface of nickel foam (NF) exhibited a high activity towards ethanol oxidation as a standalone electrode that is 10 times that of bare NF.

Comparison of various atomic compositions of Au@Pd/C, Pd/C, and AuPd/C electrocatalysts for direct ethanol fuel cells

AbstractPd/C, Au@Pd/C (core‐shell), and AuPd/C (AR—consisting in Au microparticles) were used as electrocatalysts for ethanol oxidation in alkaline medium. A synergistic effect between Au and Pd atoms in Au@Pd/C makes the binding between ethanol and Au@Pd/C stronger. This leads to product formation in higher potentials and can be useful to select ethanol products. We also showed that the atomic composition of the electrocatalysts to be used in fuel cells and in powder form to be used in electrochemical experiments are very similar, reaching high values of correlation. The depth profiling X‐ray photoelectron spectroscopy for the anode catalysts to be used in fuel cells can provide new insights about ethanol oxidation in direct ethanol fuel cells (DEFCs), for instance, metal oxide species can act in fuel cells environment. In terms of electric generation, Au@Pd/C presented a better performance in electrochemical experiments; the current density was about 1.6 times higher than the peak current density obtained for Pd/C. In terms of electrochemical stability, Au@Pd/C presented better final current density when compared to Pd/C and AuPd/C electrocatalysts. However, in DEFC experiments, Pd/C showed better performance.

Stability of Pd3Pb Nanocubes during Electrocatalytic Ethanol Oxidation

Intermetallic Pd3Pb nanocrystals with controlled size and cubic geometry exposing (100) facets are synthesized and tested as electrocatalysts for ethanol oxidation in alkaline media. We observe the...