Ethanol Electrooxidation Research Articles

Anchoring bimetallic PtAu nanoparticles on hierarchical zeolite as efficient electrocatalyst for the enhancement of ethanol electrooxidation

Zeolite materials as nanoreactor are promising candidates as catalysts for the oxidation of alcohol fuels. In the present work, the hierarchical zeolite was prepared via a hydrothermal technique. Then, the bimetallic Pt-Au-zeolite composite as electrocatalysts were synthesized by co-precipitation route. The surface morphology, composition and structure of the resulting composite were investigated by FE-SEM, EDS, XRD, XPS, BET&BJH and FT-IR. The catalytic performance of the composite has been examined in ethanol electrooxidation reactions under alkaline media. Pt-Au-zeolite exhibits superior selectivity for the electrooxidation of the ethanol, outperforming both conventional Au and Pt nanoparticles supported on zeolite crystals catalyst. The peak electrooxidation current of ethanol with Pt-Au-zeolite catalyst is 3.63 times that of Pt-zeolite with a scan rate of 50 mVs−1, which is due to the synergistic effect of Au and Pt in zeolite framework. It could be attributed to the incorporation of Au and Pt into zeolite framework, which was beneficial to the charge transferring the surface of Pt-Au-zeolite electrocatalyst and facilitated the ethanol oxidation. Besides, the significant electrochemical activity can be due to the production of OH–, which leads to the species present on the surface of the electrocatalysts during the activation process that controlled by the zeolite framework.

Electrodeposition of CoNi Bimetallic Catalyst for Ethanol Electrooxidation Application

Platinum is potentially employed as a catalyst in direct ethanol fuel cells (DEFCs). However, its scarcity and susceptibility to carbon monoxide poisoning give rise to novel challenges necessitating resolution. Transition metals such as nickel and cobalt are regarded as highly auspicious catalysts for DEFCs due to their perceived potential to reduce the expenditure associated with the synthesis procedure. In the present investigation, the synthesis of a cobalt-nickel (CoNi) catalyst with bimetallic properties was effectively accomplished through the electrodeposition technique utilizing the stimulator mode. Subsequently, an evaluation was conducted to assess the catalyst's proficiency in ethanol electrooxidation. The CoNi samples underwent comprehensive characterization through the utilization of various analytical techniques, namely X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental dispersive X-ray analysis, and electrochemical impedance spectroscopy (EIS). The XRD analysis confirmed the formation of CoNi, while the SEM characterization demonstrated that the CoNi samples exhibited a homogeneous morphological feature. The impedance measured by the EIS technique displayed a resistance to charge transfer value of 21.21 kΩ, while the solution resistance value amounted to 66.67 kΩ. The catalytic efficiency of the specimens in ethanol electrooxidation was evaluated using the cyclic voltammetry technique, resulting in a peak current density of 3.14 mA/cm2 proving the potential of bimetallic CoNi to be a low-cost catalyst for ethanol electrooxidation process.

Interface-confined precise processing of Ag nanowire into AgPd-nanoparticle-sealed AgAu nanotroughs for boosting ethanol electrooxidation

The functions of nanomaterials are closely linked with their fine structures and compositions. Precisely processing nanoparticles into morphology- and composition-varied nanostructures can a cutting-edge technology for producing complex nanostructures. Herein, we develop an interface-confined precise processing strategy towards toluene/water-interfacial Ag nanowires. Interfacial Ag nanowires are transformed into AgPd-nanoparticle-sealed AgAu nanotroughs with abundant AgPd/AgAu hetero-junctions (i.e., AgPdAu hetero-junction nanostructures). By adjusting the reaction conditions, composition-varied AgPdAu hetero-junction nanostructures can be obtained. The formation of AgPdAu hetero-junction nanostructures can be attributed to interface-confined precise etching towards Ag nanowires separately from the two subphases of the water and the toluene. Composition-optimized Ag13Pd67Au20 hetero-junction nanostructure shows satisfactory catalytic performance towards ethanol electrooxidation: ∼4 and 2 times in electrochemical-activity-surface-area-normalized activities; ∼6 and 5 times in mass-normalized activities higher than commercial Pd/C and Pt/C, respectively. The outstanding catalytic capability of Ag13Pd67Au20 may be attributed to optimized composition, porous nanostructures as well as abundant AgPd/AgAu hetero-junctions. This work demonstrates the feasibility of precisely processing interfacial nanoparticles, opening the way for creating morphology-well-defined composition-varied complex nanostructures.

Bimetallic Au–Pd nanoparticles decorated electrospun spinel CoFe2O4 nanostructures as efficient electrocatalysts for ethanol fuel oxidation in alkaline media

Spinel-based materials are promising candidates as electro-catalysts for the oxidation of alcohol fuels. In the present study, electrospun CoFe2O4 spinel nanostructures were prepared by electrospinning technique and the subsequent thermal treatment processes. Then, the bimetallic Au–Pd–CoFe2O4 composite as electro-catalysts were synthesized by precipitation method. The surface morphology, composition and structure of the resulting composite nanostructures were studied by FE-SEM, EDS, TEM, XPS, XRD and FT-IR. The catalytic performance of resultant composite has been examined in ethanol electro-oxidation reactions under alkaline conditions. The effect of different Au:Pd ratios on the electrocatalytic performance of Au–Pd–CoFe2O4 composite nanostructures for ethanol oxidation was evaluated. The synthesized composite Au–Pd–CoFe2O4 (APCo22) illustrates a superior ethanol oxidation activity in comparison to other electrocalysts, and the peak current of this spinel-type electro-catalysts is 9.89 times that of Pd–CoFe2O4 with a scan rate of 50 mVs−1, which is due to the synergistic effect of Au and Pd on CoFe2O4. Furthermore, the remarkable electrochemical property can be due to the production of OH−, which leads to the species present on the surface of the electro-catalysts during the activation process.

Synthesis of Pt-Au nanoparticles supported on reduced graphene oxide as a highly active and durability catalyst for electro-oxidation of ethanol

Design of advanced electrocatalyst, with high active and stability in electro-oxidation reactions for Direct Alcohol Fuel Cells system is urgent scientific need in the context of electrochemical energy application. Herein, Pt-Au nanoparticles supported on reduced graphene oxide, with low content of metals (With the theoretical content of 1.87% (Au) and 4.67% (Pt)), as a highly active and durability catalyst for electro-oxidation of ethanol is successfully synthesized. The current density (mass specific activity) of the PtAu/rGO catalyst for electro-oxidation ethanol, in alkaline media, was 13195 mAmgPt-1, which is 1.26 times higher than that of the Pt/rGO catalyst. After 4000s, the current density of PtAu/rGO catalyst reached 317 mAmgPt-1, is higher than that of Pt/rGO catalyst, reaching 172 mAmgPt-1. The high catalytic activity and stability of the bimetallic PtAu/rGO catalyst in the electrochemical oxidation of ethanol in alkaline medium are attributed to the synergistic effect of Au, Pt and rGO, among which, Au not only plays the role of enhancing the dispersion of Pt, but also has the effect of preventing the agglomeration of Pt nanoparticles during the reaction. This research could open up the potential to develop advanced bimetallic PtAu materials that can be used as electrochemical catalysts for various reactions.

Insights into the Rate-Determining Step of the Ethanol Electro-oxidation Reaction on the Pd(111) Surface through Ab Initio Molecular Dynamics Simulations

Insights into the Rate-Determining Step of the Ethanol Electro-oxidation Reaction on the Pd(111) Surface through Ab Initio Molecular Dynamics Simulations

Ag/Ag2O electrode for electrocatalytic oxidation of ethanol

A film of silver oxide is grown on an Ag electrode in KOH solutions, by repetitive cyclic voltammograms at a high scan rate of 2500 mV/s. The formed film is used for the electro-oxidation of ethanol in a dilute potassium hydroxide using the cyclic voltammetry technique. Some effective experimental parameters such as the ethanol concentration, KOH concentration, scanning rate, and temperature on the electrocatalytic oxidation of ethanol have been investigated and discussed. The data confirmed that the formed silver oxide electrode behaves as a good catalyst for the electrooxidation of ethanol. The mechanism of oxidation is likely to be dissociative chemisorption involving one electron transfer. The apparent activation energy, E*, for the electrooxidation, was found to be 68.23 kJ/mole, which is considered too high for a pure diffusion process and moderate for a pure adsorption process. Then the charge transfer is probably controlled by a mixed adsorption-diffusion process

Hydrogen-induced p-d orbital hybridization and tensile strain of PdGa single-atom alloy metallene boosts complete electrooxidation of ethanol

Ethanol oxidation reaction (EOR) at the anode of direct ethanol fuel cells (DEFCs) obeys C1/C2 dual-pathway reaction mechanism, and improving the selectivity of C1 pathway is crucial to the commercialization of DEFCs. Herein, a novel hydrogen-implanted PdGa single-atom alloy metallene (H-Ga1Pdene) is designed for optimizing the C1 pathway to achieve greatly enhanced C1 pathway selectivity through electronic and strain engineering. Benefiting from the strong p-d orbital hybridization interaction and tensile strain effect induced by hydrogen-implantation, H-Ga1Pdene exhibits high mass activity of 10.34 A mgPd−1 and C1 pathway selectivity of 54.7%, both showing an order of magnitude higher than that of commercial Pd/C. Theoretical calculations reveal that the p-d hybridization interaction could effectively accelerate the C-C bond cleavage and tensile strain enable efficient oxidation of CO* and CH3 * produced by the C-C bond cleavage in C1 pathway, enabling H-Ga1Pdene to efficiently catalyze the complete electrooxidation of ethanol through the C1 pathway.

Self-Interface in Rh Nanosheets-Supported Tetrahedral Rh Nanocrystals for Promoting Electrocatalytic Oxidation of Ethanol.

Direct ethanol fuel cells hold great promise as a power source. However, their commercialization is limited by anode catalysts with insufficient selectivity toward a complete oxidation of ethanol for a high energy density, as well as sluggish catalytic kinetics and low stability. To optimize the catalytic performance, rationally tuning surface structure or interface structure is highly desired. Herein, a facile route is reported to the synthesis of Rh nanosheets-supported tetrahedral Rh nanocrystals (Rh THs/NSs), which possess self-supporting homogeneous interface between Rh tetrahedrons and Rh nanosheets. Due to full leverage of the structural advantages within the given structure and construction of interfaces, the Rh THs/NSs can serve as highly active electro-catalysts with excellent mass activity and selectivity toward ethanol electro-oxidation. The in situ Fourier transform infrared reflection spectroscopy showed the Rh THs/NSs exhibit the highest C1 pathway selectivity of 23.2%, far exceeding that of Rh nanotetrahedra and Rh nanosheets. Density function theory calculations further demonstrated that self-interface between Rh nanosheets and tetrahedra is beneficial for C-C bond cleavage of ethanol. Meanwhile, the self-supporting of 2D nanosheets greatly enhance the stability of tetrahedra, which improves the catalytic stability.

A Study on significant role of Ru on MWCNT-supported PtRu electrocatalysts for ethanol electro-oxidation

A Study on significant role of Ru on MWCNT-supported PtRu electrocatalysts for ethanol electro-oxidation

Electrooxidation of methanol and ethanol catalyzed by high-performance three-dimensional graphene-supported PdM (Co, Cu) binder-free electrode

PdM/RGN (M = Co, Cu) self-supporting composite electrodes were synthesized via a simple two-step spontaneous reduction process using Ni foam as the substrate and reduced graphene oxide as support layer. The composites were characterized using X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy were performed to study the electrocatalytic activities of the prepared electrodes for methanol and ethanol oxidation. The performances of PdM/RGN for methanol and ethanol oxidation increased and then decreased as the atomic ratio of Pd to M (Co, Cu) increased. The Pd6Co1/RGN and Pd6Cu1/RGN electrodes exhibited markedly superior catalytic activity and long-term stability. The peak current densities of Pd6Cu1/RGN and Pd6Co1/RGN electrodes reached 0.36 and 0.29 A/cm2 for methanol electrooxidation and which reached 0.8 and 0.5 A/cm2 for the ethanol electrooxidation, respectively. This excellent performance is owing to the three-dimensional structure of nickel foam, the improving specific surface area and the synergistic effect between Pd and M.

Interfacial Electron Engineering of PdSn-NbN/C for Highly Efficient Cleavage of the C-C Bonds in Alkaline Ethanol Electrooxidation.

The splitting of the C-C bonds of ethanol remains a key issue to be addressed, despite tremendous efforts made over the past several decades. This study highlights the enhancement mechanism of inexpensive NbN-modified Pd1 Sn3 -NbN/C towards the C-C bonds cleavage for alkaline ethanol oxidation reaction (EOR). The optimal Pd1 Sn3 -NbN/C delivers a catalytic activity up to 43.5 times higher than that of commercial Pd/C and high carbonate selectivity (20.5%) toward alkaline EOR. Most impressively, the Pd1 Sn3 -NbN/C presents good durability even after 25 200 s of chronoamperometric testing. The enhanced catalytic performance is mainly due to the interfacial interaction between PdSn and NbN, demonstrated by multiple structural characterization results. In addition, in situ ATR-SEIRAS (Attenuated total reflection-surface enhanced infrared absorption spectroscopy) results suggest that NbN facilitates the C-C bonds cleavage towards the alkaline EOR, followed by the enhanced OH adsorption to promote the subsequent oxidation of C1 intermediates after doping Sn. DFT (density functional theory) calculations indicate that the activation barriers of the C-H bond cleavage in CH3 CH2 OH, CH3 CHOH, CH3 CHO, CH3 CO, CH2 CO, and the C-C bond cleavage in CH3 CO, CH2 CO, CHCO are evidently reduced and the removal of adsorbed CH3 CO and CO becomes easier on the PdSn-NbN/C catalyst surface.

Tuning electronic structure of Pt to enhance ethanol electrooxidation performance of SnO2 patched ultrathin PtRhNi nanowires

Tuning electronic structure of Pt to enhance ethanol electrooxidation performance of SnO2 patched ultrathin PtRhNi nanowires

Enhancing ethanol electrooxidation stability catalyzed by Pt with SnO2 modified graphene as support

Developing catalysts for the stable electrooxidation of ethanol have been a goal pursued by scientists. The present work reports a facile synthesis of catalysts with a double junction structure of Pt and SnO2 on graphene (Pt/SnO2GN) through sol–gel combined with glycol hydrothermal reduction method. The physicochemical analyses show that the reduced Pt uniformly dispersed on GN is located adjacent to SnO2 and has electronic interaction with the composite carrier. The electrochemical results exhibit that Pt/SnO2GN has better catalytic performance for ethanol electrooxidation than PtSnO2/GN and PtSn/GN. The ethanol oxidation peak current density on Pt/SnO2GN, after 1500 cycles of voltammetric testing, can still maintain 99.2% of the highest. The excellent catalytic stability of Pt/SnO2GN is ascribed to the double junction structure and the appropriate interaction between Pt and SnO2 on GN, which enlarge the ECSA of Pt, improve the structural integrity, accelerate the charge transfer kinetics and increase the CO tolerance.

Enhanced stability and efficiency of Pd electrocatalysts towards electrooxidation of ethanol using CNT–CNF supporting materials

Enhanced stability and efficiency of Pd electrocatalysts towards electrooxidation of ethanol using CNT–CNF supporting materials

Highly active and durable PdFe/Cu nanocatalysts prepared by liquid phase synthesis for ethanol electrooxidation reaction

In the face of environmental pollution and an energy shortage, how to reduce the cost of a noble metal catalyst in clean energy such as the fuel cell system and improve its electrocatalytic performance is one of the hot issues in this field. Here, a facile stepwise co-reduction route for synthesizing a series of PdFe/Cu catalysts with surface reconstruction is investigated and the ethanol oxidation reaction (EOR) performance is explored. The greater exposure of Pd active sites makes it excellent in EOR in alkaline media compared to the homemade and commercial Pd black catalyst. The mass activity of PdFe/Cu (794.97 mA mg−1Pd) is 2.52 times that of the Pd black catalyst (315.64 mA mg−1Pd). This kind of PdFe/Cu catalyst shows enhanced mass current density (255.66 mA mg−1Pd) after the 1800 s chronoamperometry test and only exhibits a decay of 1.4% after accelerated 500-cycle measurement. The enhanced EOR performance may be due to the change in the electronic structure of Pd caused by synergistic and strain effects among Pd, Fe, and Cu. This work provides an effective and kindly strategy to synthesize electrocatalysts with superior activity and durability in relation to EOR.

Structure and Reactivity of Metal-Oxide-Supported Noble Metal Nanoparticles: Electrooxidation of Simple Organic Molecules

There has been growing interest in utilizing small (simple) organic molecules, as alternative fuels to hydrogen, in electrochemical energy conversion systems. In addition to ethanol (biofuel), that can be ideally oxidized to carbon dioxide thus delivering twelve electrons, recent important systems include dimethyl ether as well. But realistically the respective reaction is rather slow at ambient conditions. Obviously, there is a need to develop novel electrocatalytic materials.Platinum has been recognized as the most active catalytic metal towards oxidation of ethanol at low and moderate temperatures. But Pt anodes are readily poisoned by the strongly adsorbed intermediates, namely by CO-type species, requiring fairly high overpotentials for their removal. To enhance activity of Pt catalysts towards methanol and ethanol oxidation, additional metals including ruthenium, tin, molybdenum, tungsten or rhodium are usually introduced as the alloying component. More recently it has been demonstrated that catalytic activity of platinum-based nanoparticles towards electrooxidation of ethanol has been significantly enhanced through interfacial modification with ultra-thin monolayer-type films of metal oxo species of tungsten, titanium or zirconium.We pursue a concept of utilization of mixed metal (e.g. zirconium/tungsten or titanium/tungsten) oxide matrices for supporting and activating noble metal nanoparticles (e.g. PtRu) during electrooxidation of methanol, ethanol, formic acid and dimethyl ether. Among important issues is incorporation of Rh nanostructures capable of weakening, or even breaking, the C-C bond in the ethanol molecules. On the other hand, rhodium itself is not directly electrocatalytic toward oxidation of ethanol. The oxides and noble metal nanoparticles have been deposited in a controlled manner using the layer-by-layer method. Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed. The most likely explanation takes into account possibility of specific interactions of noble metals with transition metal oxide species as well as existence of active hydroxyl groups in the vicinity of catalytic noble metal sites. In addition, formation of “nanoreactors” where ethanol is partitioned (at Rh) to methanolic residues further oxidized at PtRu cannot be excluded.

(Invited) Kinetic Modeling of Ethanol Electro-Oxidation on Co-Ni-Mo-P Electrocatalyst

A rotating disk electrode technique was used to study the kinetics of ethanol electro-oxidation on multi-alloy composition of CoNiMoP deposited on catalyzed carbon substrate (CCS). A simple kinetic model for ethanol oxidation on CoNiMoP/CCS was developed with the assumption of a simultaneous generation of two main products – CH3CHO (acetaldehyde) and CH3COOH (acetic acid) and the experimental result was used to evaluate the kinetic parameters of the model. In the developed model, if only one of the two products- CH3CHO or CH3COOH was generated, the result showed that at high ethanol concentration, the ethanol reaction mechanism followed the acetaldehyde route while at low ethanol concentration, the mechanism led to acetic acid and carbon dioxide route. However, a modified model in which a simultaneous production of both CH3CHO and CH3COOH occurred, showed that ethanol oxidized rapidly to CH3COOH. Additionally, the effect of the rotation speed (400 or 900 rpm) on the reaction was investigated and the result showed that the speed did not affect the mechanism because the experimental results were closer to the CH3COOH curves for both cases (400 and 900 rpm), but rotation speed affected the mole fraction of CH3COOH and CH3CHO.

(Digital Presentation) Ethanol Electro-Oxidation Kinetics Using Activated Carbon-Supported Pt-Ag Catalysts in Alkaline Media

Due to scarcity of fossil fuels and their severe environmental consequences, the development of high efficiency energy conversion devices such as fuel cells (FCs) have gained considerable attention. The specific energy conversion efficiency of FC is highly influenced by the activity of the electrocatalysts. The Pt is widely used as an electrocatalyst due to its high activity and stability, but its high cost and depletion of resources hinder its commercialization. One of the workable strategies for the practical application of Pt is to reduce its content by alloying with some non-precious metals and simultaneously maintain its electrochemical performance. In this context, we developed a low Pt-loaded Pt-Ag/C alloy electrocatalyst via a gradual reduction process. The electrochemical performance of the as-synthesized catalyst was investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) using the three-electrode electrochemical workstation at room temperature. The electrocatalytic investigations reveal that the resultant alloy has an activity of 32.7 mA cm-2, which is significantly higher than that of Pt/C (17.6 mA cm-2) in an alkaline electrolyte and makes it a very efficient electrocatalyst for the ethanol oxidation reaction (EOR). The partial electron transfer from Ag to Pt in Pt-Ag alloy, which weakens the CO binding and poisoning effect on the surface, may be partly responsible for the enhanced catalytic activity of Pt-Ag/C. The activated carbon support also favors charge transport by transferring charge from catalytic active sites to external circuits. The stability and durability studies reveal that Pt-Ag/C performs significantly better than Pt/C, making it a viable electrocatalyst for EOR. Keywords: Direct Ethanol Fuel Cell, Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, Alloy.

Oxygen-Bridged Long-Range Dual Sites Boost Ethanol Electrooxidation by Facilitating C-C Bond Cleavage.

Optimizing the interatomic distance of dual sites to realize C-C bond breaking of ethanol is critical for the commercialization of direct ethanol fuel cells. Herein, the concept of holding long-range dual sites is proposed to weaken the reaction barrier of C-C cleavage during the ethanol oxidation reaction (EOR). The obtained long-range Rh-O-Pt dual sites achieve a high current density of 7.43 mA/cm2 toward EOR, which is 13.3 times that of Pt/C, as well as remarkable stability. Electrochemical in situ Fourier transform infrared spectroscopy indicates that long-range Rh-O-Pt dual sites can increase the selectivity of C1 products and suppress the generation of a CO intermediate. Theoretical calculations further disclose that redistribution of the surface-localized electron around Rh-O-Pt can promote direct oxidation of -OH, accelerating C-C bond cleavage. This work provides a promising strategy for designing oxygen-bridged long-range dual sites to tune the activity and selectivity of complicated catalytic reactions.