Ethanol Electrooxidation Research Articles

Easy fabrication of a novel electro-spun PVDF-g-C3N4-Pd nanocomposite material as improved anode electrocatalyst for direct alcohol fuel cell

In this study, we account a simple, effortless one-step electrospinning process to prepare high-performance poly(vinylidene fluoride)-graphitic carbon nitride/palladium (PVDF-g-C3N4-Pd) nanocomposite fibers (NCFs) for methanol and ethanol electro-oxidation process. As-synthesized PVDF-g-C3N4-Pd NCFs were examined to ensure its physicochemical assets such as surface morphology, structural geometry, elemental structure, and thermal stability. The acquired long and continuous NCFs morphology with elemental and structural results authenticates the successful fabrication of PVDF-g-C3N4-Pd NCFs. Holding to the substantial synergistic effects of each component in the PVDF-g-C3N4-Pd NCFs electrocatalyst displays forward peak current densities as high as 0.53 mA/cm2 and 10.50 mA/cm2 for methanol and ethanol electro-oxidation reactions, respectively, far outperforming than PVDF-g-C3N4 NCFs electrocatalyst. Also, PVDF-g-C3N4-Pd NCFs exhibit reliable mechanical stability and as well as thermal stability and could possibly open up an excellent high-performance portable fuel cell system for DAFCs application.

Insights on the C2 and C3 electroconversion in alkaline medium on Rh/C catalyst: in situ FTIR spectroscopic and chromatographic studies

The present work evaluates ethanol and glycerol electro-oxidation on Rh/C catalysts prepared using the Bromide Anion Exchange (BAE) method. Physicochemical characterizations were performed using Thermogravimetric Analysis (TGA), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The SPAIRS investigations revealed that the CO adsorption modes on Rh sites occur on the linearly adsorbed CO (COL) and bridged bonded (COB) modes. In ethanol oxidation reaction (EOR), the Rh effect was evaluated by analyzing the products generated after bulk electrolysis using High-Performance Liquid Chromatography (HPLC) and in situ FTIR spectroscopy. The results confirmed the C-C cleavage Rh ability at low potentials and revealed that EOR follows both reaction pathways on Rh/C. While in glycerol oxidation reaction (GOR), Rh addition increases high added-value products formation such as glycerate ion. The GOR main route follows the glyceraldehyde pathway. The results highlighted that Rh is a good candidate for ethanol and glycerol electrochemical conversion at low potentials.

Caustic aqueous phase electrochemical reforming (CAPER) of ethanol for process intensified compressed hydrogen production

The Caustic Aqueous Phase Electrochemical Reforming (CAPER) process can convert aqueous-phase ethanol to high-pressure and high-purity hydrogen (H2) at lower cell operating temperatures and voltages than traditional methods. Additionally, any carbon dioxide (CO2) produced by the ethanol electrochemical oxidation is captured by the caustic electrolyte solution. Without using a membrane, the only gas-phase species is H2. The CAPER process achieves process intensification for compressed and pure H2 production by eliminating the need for downstream separation and external compression steps. All the compression is performed on the liquid-phase reactants to circumvent less efficient gas-phase compression. This study uses a high-pressure batch electrochemical reactor to demonstrate the capability of the CAPER reforming process and investigates catalytic behavior under operating conditions. Our Tafel analysis showed that both palladium and platinum nanoparticles on carbon supports have high activity for ethanol electrooxidation under the caustic electrolyte condition (exchange current density (i0) > 1 × 10−5 A cm−2), while non-noble nanoparticles on carbon supports showed poor activity. The only gas phase product was pressurized H2 and its faraday efficiency was determined as 100%. The exchange current density was not affected by high-pressure operation. The carbon selectivity toward unwanted byproduct acetate on the anode increased from 17% to 63% as the applied anode potential increased from −500 mV to −200 mV vs. Ag/AgCl.

Enhancing Ethanol Electrooxidation Stability over PtIr/GN Catalysts by In Situ Formation of IrO2 at Adjacent Sites

PtIr alloy is considered as one of the most promising catalysts for ethanol electrooxidation due to its excellent C–C bond breaking and dehydrogenation abilities. However, a small amount of intermediate species produced by ethanol oxidation can still poison Pt, thereby affecting the stability of ethanol oxidation. Here, graphene supported PtIr nanoparticles (PtIr/GN) with a Pt: Ir atomic ratio of 3:1 is synthesized by a simple hydrothermal reduction and thermal annealing. The physicochemical analyses show that IrO2 is formed in situ in PtIr/GNs (O) during annealing and located adjacent to PtIr alloys. IrO2 and PtIr are evenly dispersed on GNs. The electrochemical results indicate that PtIr/GNs (O) has higher catalytic activity and stability for ethanol electrooxidation than PtIr/GNs. After 1000 voltammetric cycles, the peak current density for PtIr/GNs (O) is 2.5 times higher than that for PtIr/GNs. The outstanding electrochemical performance of PtIr/GNs (O) is derived from PtIr alloy that promotes the cleavage of the C–C bond and weakens the adsorption of Pt to intermediate species, IrO2 that improves the tolerance of Pt to CO-like species and enhances the structural stability of Pt, and PtIr alloy and IrO2 in adjacent positions that synergistically improve the stability of catalytic ethanol oxidation.

Facile synthesis of porous PtRu colloid for enhanced methanol and ethanol electrooxidation

Facile synthesis of porous PtRu colloid for enhanced methanol and ethanol electrooxidation

Gold–rhodium nanoflowers for the plasmon enhanced ethanol electrooxidation under visible light for tuning the activity and selectivity

Direct ethanol fuel cells (DEFCs) are a promising power source, but the low selectivity to ethanol complete oxidation is still challenging. The localized surface plasmon resonance (LSPR) excitation has been reported to accelerate and drive several chemical reactions, including the ethanol oxidation reaction (EOR), coming as a strategy to improve catalysts performance. Nonetheless, metallic nanoparticles (NPs) that present the LSPR excitation in the visible range are known for leading to the incomplete oxidation of ethanol. Thus, we report here the application of gold-rhodium nanoflowers (Au@Rh NFs) towards the plasmon-enhanced EOR. These hybrid materials consist of a Au spherical nucleus covered by Rh branches shell, combining plasmonic and catalytic properties. Firstly, the Au@Rh NFs metallic ratio was investigated in dark conditions to obtain an optimal catalyst. Experiments were also performed under light irradiation. Our data demonstrated an improvement of 352% in current density and 36% in selectivity to complete ethanol oxidation under 533 nm laser incidence. Moreover, the current density showed a linear increase with the laser power density, indicating a photochemical effect and thus enhancement due to the LSPR properties.

Enhancing solar-driven photoelectrocatalytic efficiency of Au nanoparticles with defect-rich hydrogenated TiO2 toward ethanol oxidation

It is significant to promote the efficiency of solar fuel cells via improving the utilization of solar in photoelectrocatalysis. In this work, hydrogenated TiO2 (H-TiO2) nanoparticles with Ti3+ and/or oxygen vacancy (VO) defects were obtained and have extended light absorption to visible light region. As a photochemical component, H-TiO2 was further coupled with Au nanoparticles to assemble photoelectrocatalyst to apply in photo-assisted electrooxidation of ethanol. Due to the existence of defects in H-TiO2, the peak current density on Au/H-TiO2 is improved by 5.4% with the assistance of light irradiation, and even up to 18.3% under simulated sunlight illumination, which is much higher than that on Au/W-TiO2 (W-TiO2 loaded Au) under the light irradiation. Meanwhile, it is demonstrated that the charge transfer is improved on Au/H-TiO2 with Vo due to the existence of Vo, improving the separation of excited electrons and holes. Density function theory (DFT) based theoretical calculations illustrate that the energy barrier of reaction intermediates on Au-TiO2 with Vo defects is lower than that without Vo, indicating that Au-TiO2 with Vo is more energetically favorable. This work highlights the possibility of using defective semiconductor nanomaterials to combine photocatalysis and electrocatalysis in solar fuel cells and to further improve the efficiency of fuel cells under solar full spectrum.

Roles of hydroxyl and oxygen vacancy of CeO2·xH2O in Pd-catalyzed ethanol electro-oxidation

Roles of hydroxyl and oxygen vacancy of CeO2·xH2O in Pd-catalyzed ethanol electro-oxidation

Branch-Regulated Palladium-Antimony Nanoparticles Boost Ethanol Electro-oxidation to Acetate.

Tuning the composition and morphology of bimetallic nanoparticles (NPs) offers an effective strategy to improve their electrocatalytic performance. In this work, we present a facile wet-chemistry procedure to engineer PdSb NPs with controlled morphology. Spherical or branched NPs are produced by tuning the heterogeneous nucleation of Sb on Pd seeds. Compared with pure Pd NPs, the incorporation of Sb not only decreases the amount of Pd used but also results in a significant increase of activity and stability for the electrocatalytic ethanol oxidation reaction (EOR). Best performances are obtained with highly branched PdSb NPs, which deliver a specific activity of 109 mA cm-2 and a mass activity of up to 2.42 A mgPd-1, well above that of a commercial Pd/C catalyst and branched Pd NPs. Moreover, PdSb displays significant stability enhancement of over 10 h for the EOR measurements. Density functional theory calculations reveal that the improved performance of PdSb NPs is related to the role played by Sb in reducing the energy barrier of the EOR rate-limiting step. Interestingly, as a side and value-added product of the EOR, acetate is obtained with 100% selectivity on PdSb catalysts.

Self-Assembled Pt/MoCx/MWCNTs Nano Catalyst for Ethanol Electrooxidation of Fuel Cells.

Direct ethanol fuel cells (DEFCs) have attracted more and more attention because of their unique advantages such as low cost and low toxicity. However, sluggish C-C bond cleavage during the ethanol electrooxidation reaction (EOR) in acidic media results in a lower energy yield and gravely hinders the commercialization of DEFCs. Therefore, it is very necessary to develop an anode catalyst with high performance, high stability and low cost to solve this problem. In this paper, Pt/MoCx/MWCNTs nanocomposites with different mass ratios of PtMo were obtained through a molecular self-assembly technology. The structure and morphology of Pt/MoCx/MWCNTs nanocomposites were characterized by several techniques such as XRD, FESEM, XPS, etc. The electrochemical performance and stability of Pt/WCx/MWCNTs electrocatalysts toward EOR were investigated in acid electrolytes. The results show that PtMo exists in the form of alloy. The size of Pt/MoCx nanoparticles is very uniform with an average size of ∼24 nm. The Pt/MoC0.25/MWCNTs exhibits excellent electrocatalytic activities with an electrochemically active surface area of 37.1 m2 g−1, a peak current density of 610.4 mA mgPt −1 and a steady-state current density of 39.8 mA mgPt −1 after 7,200 s, suggesting that the Pt/MoC0.25/MWCNTs is a very promising candidate for application in EOR of DEFCs.

Assembly of Alloyed PdCu Nanosheets and Their Electrocatalytic Oxidation of Ethanol.

Two-dimensional (2D) nanostructured catalysts have attracted great attention in many important fields, including energy applications and chemical industry. In this study, PdCu nanosheet assemblies (NSAs) have been synthesized and investigated as electrocatalysts for direct ethanol fuel cells in an alkaline medium. A great number of active sites on the nanosheets of PdCu NSAs for ethanol electro-oxidation are exposed, where the electron structures are optimized combined with the second element copper. Electrochemical measurements show that PdCu NSA1 exhibits excellent catalytic activity (2536 mA mg-1) and cyclic stability compared to PdCu NSA2 (1700 mA mg-1) and PdCu NSA3 (1436 mA mg-1), much higher than commercial Pd/C. Kinetics studies on the electrolysis of ethanol suggest that PdCu NSAs should be more favorable at higher catalytic temperatures, higher concentrations of ethanol, and low pH value environments. The unique composition and structures PdCu NSA1 would result in the lowest energy barrier in the rate-controlling step of the ethanol oxidation reaction (EOR), confirmed by density functional theory (DFT). The formation mechanism of PdCu NSAs and their excellent electrocatalytic activity toward EOR have been discussed and analyzed.

Synthesis of Pt-CuO/RuO2 composites by dealloying from metallic glass and their ethanol electrooxidation performance

Synthesis of the noble metal-based catalyst with a multi-composite system, unique structure, and special morphology is very important for boosting the catalytic performance while reducing the noble metal use. Here, attractive island/nanosheet structural Pt-CuO/RuO2 composites were constructed on the surface of Cu-Al-Ce-based metallic glass ribbons containing a small amount of Pt and Ru by dealloying. The surface morphology of these binder-free, self-supported flexible hybrid electrocatalysts can be facilely regulated in a controllable way. Electrochemical measurements revealed the islands-nanosheets/glassy hybrid electrocatalysts obtained from Cu60Al10Ce26Pt3Ru1 MG ribbon exhibit superior electrocatalytic performance toward ethanol oxidation with a high current density of ∼215 mA⋅cm−2 and better stability, outperforming commercial Pt/C and other dealloyed products. This can be attributed to the enlarged surface area, the abundant Pt-rich active sites, and the synergistic effects of Pt, Ru/RuO2, and CuO in the removal of poisoning intermediates. This work provides a new perspective for the design of high-active binder-free composite catalysts based on multicomponent metallic glass with low noble metal usage.

Tailoring porous/filament silicon using the two-step Au-assisted chemical etching of p-type silicon for forming an ethanol electro-oxidation layer

In this paper, we are reporting on the fabrication of a porous silicon/Au and silicon filament/Au using the two-step Au-assisted chemical etching of p-type Si with a specific resistivity of 0.01, 1, and 12 Ω·cm when varying the Au deposition times. The structure analysis results show that with an increasing Au deposition time of up to 7 min, the thickness of the porous Si layer increases for the same etching duration (60 min), and the morphology of the layer changes from porous to filamentary. This paper shows that the uniform macro-porous layers with a thickness of 125.5–171.2 μm and a specific surface area of the mesopore sidewalls of 142.5–182 m2·g−1 are formed on the Si with a specific resistivity of 0.01 Ω·cm. The gradient macro-porous layers with a thickness of 220–260 μm and 210–290 μm, the specific surface area of the mesopore sidewalls of 3.7–21.7 m2·g−1 and 17–29 m2·g−1 are formed on the silicon with a specific resistivity of 1 and 12 Ω·cm, respectively. The por-Si/Au has excellent low-temperature electro oxidation performance with ethanol, the activity of ethanol oxidation is mainly due to the synergistic effect of the Au nanoparticles and porous Si. The formation mechanism of the uniform and gradient macro-porous layers and ethanol electro-oxidation on the porous/filament silicon, decorated with Au nanoparticles, was established. The por-Si/Au structures with perpendicularly oriented pores, a high por-Si layer thickness, and a low mono-Si layer thickness (with a specific resistivity of 1 Ω·cm) are optimal for an effective ethanol electro-oxidation, which has been confirmed with chronoamperometry measurements.

Achieving complete electrooxidation of ethanol by single atomic Rh decoration of Pt nanocubes.

SignificanceDirect ethanol fuel cells are attracting growing attention as portable power sources due to their advantages such as higher mass-energy density than hydrogen and less toxicity than methanol. However, it is challenging to achieve the complete electrooxidation to generate 12 electrons per ethanol, resulting in a low fuel utilization efficiency. This manuscript reports the complete ethanol electrooxidation by engineering efficient catalysts via single-atom modification. The combined electrochemical measurements, in situ characterization, and density functional theory calculations unravel synergistic effects of single Rh atoms and Pt nanocubes and identify reaction pathways leading to the selective C-C bond cleavage to oxidize ethanol to CO2. This study provides a unique single-atom approach to tune the activity and selectivity toward complicated electrocatalytic reactions.

B, N Co-Doping Sequence: An Efficient Electronic Modulation of the Pd/MXene Interface with Enhanced Electrocatalytic Properties for Ethanol Electrooxidation.

Improving the electrocatalytic properties by regulating the surface electronic structure of supported metals has always been a hot issue in electrocatalysis. Herein, two novel catalysts Pd/B-N-Ti3C2 and Pd/N-B-Ti3C2 are used as the models to explore the effect of the B and N co-doping sequence on the surface electronic structure of metals, together with the electrocatalytic properties of ethanol oxidation reaction. The two catalysts exhibit obviously stratified morphology, and the Pd nanoparticles having the same amount are both uniformly distributed on the surface. However, the electron binding energy of Ti and Pd elements of Pd/B-N-Ti3C2 is smaller than that of Pd/N-B-Ti3C2. By exploring the electrocatalytic properties for EOR, it can be seen that all the electrochemical surface area, maximum peak current density, and antitoxicity of the Pd/B-N-Ti3C2 catalyst are much better than its counterpart. Such different properties of the catalysts can be attributed to the various doping species of B and N introduced by the doping sequence, which significantly affect the surface electronic structure and size distribution of supported metal Pd. Density functional theory calculations demonstrate that different B-doped species can offer sites for the H atom from CH3CH2OH of dehydrogenation in Pd/B-N-Ti3C2, thereby facilitating the progress of the EOR to a favorable pathway. This work provides a new insight into synthesizing the high-performance anode materials for ethanol fuel cells by regulating the supported metal catalyst with multielement doping.

Electrooxidation of ethanol and acetaldehyde in neutral electrolyte, an infrared study

• EOR in neutral electrolyte takes place via C1 and C2 pathways. • In situ FTIR reveal the formation of CO adsorbed on the Pt surface at low potentials. • The scission of the C-C bond of ethanol takes place at ca. 300 mv. • Acetic acid is the main reaction product of the EOR or AOR at high potentials. The electrooxidation of ethanol (EOR) in neutral media is attracting a great deal of attention, especially in the area of micro devices and microbial fuel cells. In this work we study the EOR with Pt/C in neutral electrolyte and followed the evolution of the species formed with the potential by in situ FTIR. The EOR in neutral electrolyte displays higher overpotentials than in acid electrolyte but follows a similar reaction pathway, producing mainly C1 species (CO ad , CO 2 ) and C2 species (acetaldehyde, and acetic acid). The scission of the C C bond of ethanol takes place at 200 mV, a potential higher than in acid electrolyte. According to the FTIR experiments, the production of acetaldehyde during the EOR is higher than that of acetic acid. We have also studied the electrooxidation of acetaldehyde (AOR) in a neutral medium with FTIR. We observed the production of CO ad at 300 mV which is oxidized to CO 2 from E ≥ 700 mV.

MoS2/Ni3S2/Reduced Graphene Oxide Nanostructure as an Electrocatalyst for Alcohol Fuel Cells

The development of active and stable catalysts is essential for the commercialization of direct alcohol fuel cells. In this work, we introduce a MoS2/Ni3S2/rGO catalyst as a cost-effective, stable, and high-performance catalyst for application in alcohol fuel cells. MoS2/Ni3S2 and its hybrid with reduced graphene oxide (rGO) are synthesized and evaluated as nanocatalysts in the alcohol (methanol and ethanol) electro-oxidation process in alkaline media. The effects of temperature and scanning rate are investigated. Voltammetry results show that MoS2/Ni3S2/rGO has good catalytic efficiency and excellent stability of 106 and 104% after 200 consecutive CV cycles for MOR and EOR, respectively. The synergic effect of starfish Ni3S2 and the coated porous MoS2 facilitates the absorption of hydroxyl ions and alcohols on the surface of the catalyst, while rGO enlarges the specific surface area and the electrical conductivity of the electrocatalyst.

Five-fold twinned Ir-alloyed Pt nanorods with high C1 pathway selectivity for ethanol electrooxidation

Five-fold twinned Ir-alloyed Pt nanorods with high C1 pathway selectivity for ethanol electrooxidation

Hierarchical AgAu alloy nanostructures for highly efficient electrocatalytic ethanol oxidation

The ethanol oxidation reaction is a significant anodic reaction for direct alcohol fuel cells. The most commonly used catalysts for this reaction are Pt-based materials; however, Pt-based electrocatalysts cause carbon monoxide poisoning with intermediates before the complete transformation of alcohol to CO2. Herein, we present hierarchical AgAu bimetallic nanoarchitectures for ethanol electrooxidation, which were fabricated via a partial galvanic reduction reaction between Ag and HAuCl4. The ethanol electrooxidation performance of the optimal AgAu nanohybrid was increased to 1834 mA mg−1, which is almost 10 times higher than that of the pristine Au catalyst (190 mA mg−1) in alkaline solutions. This was achieved by introducing Ag into the Au catalyst and controlling the time of the replacement reaction. The heterostructure also presents a higher current density than that of commercial Pt/C (1574 mA mg−1). Density functional theory calculations revealed that the enhanced activity and stability may stem from unavoidable defects on the surface of the integrated AgAu nanoarchitectures. Ethanol oxidation reactions over these defects are more energetically favorable, which facilitates the oxidative removal of carbonaceous poison and boosts the combination with radicals on adjacent Au active sites.

Synthesis and Characterization of NiCoPt/CNFs Nanoparticles as an Effective Electrocatalyst for Energy Applications.

In this work, three nanoparticle samples, Ni4Co2Pt/CNFs, Ni5CoPt/CNFs and Ni6Pt/CNFs, were designed according to the molar ratio during loading on carbon nanofibers (CNFs) using electrospinning and carbonization at 900 °C for 7 h in an argon atmosphere. The metal loading and carbon ratio were fixed at 20 and 80 wt%, respectively. Various analysis tools were used to investigate the chemical composition, structural, morphological, and electrochemical (EC) properties. For samples with varying Co%, the carbonization process reduces the fiber diameter of the obtained electrospun nanofibers from 200–580 nm to 150–200 nm. The EDX mapping revealed that nickel, platinum, and cobalt were evenly and uniformly incorporated into the carbonized PVANFs. The prepared Ni-Co-Pt/CNFs have a face-centered cubic (FCC) structure with slightly increased crystallite size as the Co% decreased. The electrocatalytic properties of the samples were investigated for ethanol, methanol and urea electrooxidation. Using cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance measurements, the catalytic performance and electrode stability were investigated as a function of electrolyte concentration, scan rate, and reaction time. When Co is added to Ni, the activation energy required for the electrooxidation reaction decreases and the electrode stability increases. In 1.5 M methanol, the Ni5CoPt/CNFs electrode showed the lowest onset potential and the highest current density (30.6 A/g). This current density is reduced to 28.2 and 21.2 A/g for 1.5 M ethanol and 0.33 M urea, respectively. The electrooxidation of ethanol, methanol, and urea using our electrocatalysts is a combination of kinetic/diffusion control limiting reactions. This research provided a unique approach to developing an efficient Ni-Co-Pt-based electrooxidation catalyst for ethanol, methanol and urea.