Electrocatalysts For Ethanol Oxidation Reaction Research Articles

Palladium/coconut husk biochar composite material as an effective electrocatalyst for ethanol oxidation reaction

This study utilised coconut husk biochar as an alternative sustainable carbon support for Pd-based electrocatalyst for ethanol oxidation reaction in basic medium. Coconut husk biochar (BC) was prepared via slow pyrolysis at 800 °C for 1 h at a ramp rate of 5 °C min−1. The Pd/BC catalyst was prepared via borohydride-facilitated reduction of palladium chloride solution. TEM analysis revealed good dispersion of the Pd nanoparticles on the biochar support with particle size ranging from 1.9 to 3.4 nm. Cyclic voltammetry (CV) measurements of Pd/BC in 1.0 M ethanol in 0.1 M KOH gave an on-set potential of −0.615 V (versus Ag/AgCl) with a forward peak current density of 23.87 mA cm−2, which is slightly higher than the commercial Pd/C catalyst. The Pd/BC also has a higher electrochemical stability and durability than the commercial Pd/C catalyst based on chronoamperometry studies (i.e., 44.43% versus 39.64% current retention). The synthesised coconut husk biochar–supported Pd catalyst exhibited promising results for ethanol oxidation reaction for alkaline direct ethanol fuel cell application.

Materials space-tectonics methodology of conductive mesoporous carbon nanohorns embedded graphene aerogels anchoring Pd nanocrystalline for an efficient ethanol oxidation reaction

Materials space-tectonics (MST) methodology is a powerful strategy to design catalytic materials synthesis to overcome the limitation of monotonous pore geometries and develop functional structures with surface-specific functions. Based on the MST, herein, carbon nanohorns (CNH) as “spacers” inserted into three-dimensional (3D) nitrogen-doped graphene aerogel (NG) anchoring Pd nanocrystalline (Pd/CNH@NG) was constructed through a facile hydrothermal approach and wet chemical reduction method without surfactant and employed as electrocatalyst for ethanol oxidation reaction (EOR). The introduction of CNH can provide important mesopore and macropore characters and generate more active sites to anchor Pd nanocrystalline on the basis of unique internal and interstitial nanopore structures, high surface area and conductive graphitic structure, then enhancing the electrocatalytic efficiency, stability and poison tolerance of catalysts. Meanwhile, the role of CNH doped NG also includes accelerating the reaction of the intermediate (CH3COads) manufactured on the Pd-based aerogels surface with adsorbed hydroxyl (OHads) due to coordination effect from Pyridinic-nitrogen and pyrrolic-nitrogen species. The electrochemical results reveal that the specific and mass activities of the obtained Pd/CNH@NG-2 aerogel (the mass ratio of graphene oxide and CNH is 1:3) are 1.38 and 2.86 times higher than those of the commercial Pd/C for EOR. Simultaneously, the current density of Pd/CNH@NG-2 still maintains 70 % after 500 cycles of complete CV, but commercial Pd/C only maintains 22.6 % of the initial activity. The synthesis of Pd/CNH@NG not only offers a porous three-dimensional aerogel for the EOR but also optimizes a facile strategy to fabricate superior supports for promoting the commercialization of DEFCs.

NiO coupled with CeO2 as an efficient electrocatalysts for ethanol oxidation in hybrid water splitting

Replacing oxygen evolution reaction (OER) by ethanol oxidation reaction (EOR) is an effective strategy to reduce energy consumption in water splitting. Thus, a heterostructure composed of NiO nanosheets and CeO2 nanorods (NRs) (NiO@CeO2) are preapred by hydrothermal method as an efficient electrocatalyst for EOR. Characterization and electrochemical results suggest that NiO@CeO2 shows enhanced EOR performance due to the synergistic effect, which deliver current density (j) of 10 mA cm-2 at only 1.37 V, much smaller than that of NiO and CeO2. So, NiO@CeO2-based electrode shows a low cell voltage (1.39 V@ 10 mA cm-2) for overall water splitting (OWS).

(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.

Cryogels from Pt/γ-Fe2O3 and Pd/γ-Fe2O3 NPs as Promising Electrocatalysts for Ethanol Oxidation Reaction

Cryogels from noble metal NPs have proven to be highly efficient catalysts due to their high specific surface area which increases the mass transfer channels and catalytic active sites. By using metal oxides as co-catalysts, the costs of the material can be significantly reduced, while the catalytic activity can remain the same or even improve due to synergetic effects. In this work, we synthesize different cryogel thin films supported on modified ITO substrates from Pt, Pd nanoparticles (NPs), and mixtures of these noble metals with γ-Fe2O3 NPs in a very low concentration (1 wt% of the noble metal). Structural and elemental analysis of the samples are performed, along with the measurement and analysis of their catalytic activity. The electrocatalytic activity of the cryogels towards ethanol oxidation reaction (EOR) in alkaline media was evaluated by means of cyclic voltammetry. By mixing γ-Fe2O3 NPs with Pt or Pd NPs in the cryogel structure, we observe increased tolerance against poisonous surface intermediates produced during the EOR. Moreover, we observe an increase in the catalytic activity towards EOR in the case of the 1 wt% Pd/γ-Fe2O3 cryogel, making them promising materials for the development of direct ethanol fuel cells.

Efficient promotion of ethanol complete electrooxidation by anti-poisoning rhodium-bismuth alloy nanodendrites

Alkaline direct ethanol fuel cells are promising future energy technologies with a high energy-density, while the lack of robust anodic electrocatalysts limits their energy conversion efficiency due to serious poisoning and weak selectivity to the C1 pathway of ethanol oxidation reaction (EOR). Herein, rhodium-bismuth alloy nanodendrites (RhBi-NDs) are applied as an efficient and anti-poisoning electrocatalyst for EOR, which exhibit superior electrocatalytic performance, including a mass activity of 1068.9 mA mgRh−1 at 0.71 V, a 31.1% Faradaic efficiency for the C1 product, and an excellent stability of 40 h. The mechanism study indicates that Bi improves the oxidation ability of Rh to toxic intermediates by providing oxygen-containing species. The theoretical calculations disclose the electronic interaction between Bi and Rh, which tunes the adsorption energy of intermediates such as CH3CH2OH*, and CH3CO*, resulting in the suppression of C2 pathway and the promotion of C1 pathway for EOR on RhBi-NDs.

Palladium metallene confined on MXene with increased hydroxyl binding strength for highly efficient ethanol electrooxidation

Rational design and synthesis of high-performance electrocatalysts for ethanol oxidation reaction (EOR) is crucial to large-scale commercialization of direct ethanol fuel cells, but it is still an incredible challenge. Herein, a unique Pd metallene/Ti3C2Tx MXene (Pdene/Ti3C2Tx)-supported electrocatalyst is constructed via an in-situ growth approach for high-efficiency EOR. The resulting Pdene/Ti3C2Tx catalyst achieves an ultrahigh mass activity of 7.47 A mgPd-1 under alkaline condition, as well as high tolerance to CO poisoning. Insitu attenuated total reflection-infrared spectroscopy studies combined with density functional theory calculations reveal that the excellent EOR activity of Pdene/Ti3C2Tx catalyst is attributed to the unique and stable interfaces which reduce the reaction energy barrier of *CH3CO intermediate oxidation and facilitate oxidative removal of CO poisonous species by increasing the Pd-OH binding strength.

CoFe-Layered Double Hydroxide Coupled with Pd Particles for Electrocatalytic Ethanol Oxidation.

Electrocatalytic efficiency and stability have emerged as critical issues in the ethanol oxidation reaction (EOR) of direct ethanol fuel cells. In this paper, Pd/Co1Fe3-LDH/NF as an electrocatalyst for EOR was prepared by a two-step synthetic strategy. Metal-oxygen bonds formed between Pd nanoparticles and Co1Fe3-LDH/NF guaranteed structural stability and adequate surface-active site exposure. More importantly, the charge transfer of the formed Pd-O-Co(Fe) bridge could effectively modulate the electrical structure of hybrids, improving the facilitated absorption of OH- radicals and oxidation of COads. Benefiting from the interfacial interaction, exposed active sites, and structural stability, the observed specific activity for Pd/Co1Fe3-LDH/NF (17.46 mA cm-2) was 97 and 73 times higher than those of commercial Pd/C (20%) (0.18 mA cm-2) and Pt/C (20%) (0.24 mA cm-2), respectively. Besides, the jf/jr ratio representing the resistance to catalyst poisoning was 1.92 in the Pd/Co1Fe3-LDH/NF catalytic system. These results provide insights into optimizing the electronic interaction between metals and the support of electrocatalysts for EOR.

Self-supporting trimetallic PtAuBi aerogels as electrocatalyst for ethanol oxidation reaction

The creation of anodic ethanol oxidation reaction catalysts with superior all-around performance for direct ethanol fuel cells (DEFCs) has continued to attract the attention of researchers. An ultrathin trimetallic PtAuBi aerogel with branching, rough-surfaced 1D nanowires that self-assemble into a 3D porous network structure has been created in this study. It has a mass activity (MA) of 8045 mA mgPt−1 in an alkaline medium, which is 7.56 times greater than that of commercial Pt/C (1064 mA mgPt−1). Notably, the catalytic activity and resistance to CO poisoning of PtAuBi aerogels are improved by the addition of an efficient “active additive” Au. The results analysis reveals that the increased performance of PtAuBi aerogel is mostly attributable to the integrated function of the 3D porous network structure, the downward shift of the Pt d-band center, and the synergistic effect of the “Pt–Bi” and/or “Pt–Au” dual active sites.

Bimetallic AgPt Nanoalloys as an Electrocatalyst for Ethanol Oxidation Reaction: Synthesis, Structural Analysis, and Electro-Catalytic Activity.

In the present work, the chemical synthesis of AgPt nanoalloys is reported by the polyol method using polyvinylpyrrolidone (PVP) as a surfactant and a heterogeneous nucleation approach. Nanoparticles with different atomic compositions of the Ag and Pt elements (1:1 and 1:3) were synthesized by adjusting the molar ratios of the precursors. The physicochemical and microstructural characterization was initially performed using the UV-Vis technique to determine the presence of nanoparticles in suspension. Then, the morphology, size, and atomic structure were determined using XRD, SEM, and HAADF-STEM techniques, confirming the formation of a well-defined crystalline structure and homogeneous nanoalloy with an average particle size of less than 10 nm. Finally, the cyclic voltammetry technique evaluated the electrochemical activity of bimetallic AgPt nanoparticles supported on Vulcan XC-72 carbon for the ethanol oxidation reaction in an alkaline medium. Chronoamperometry and accelerated electrochemical degradation tests were performed to determine their stability and long-term durability. The synthesized AgPt (1:3)/C electrocatalyst presented significative catalytic activity and superior durability due to the introduction of Ag that weakens the chemisorption of the carbonaceous species. Thus, it could be an attractive candidate for cost-effective ethanol oxidation compared to commercial Pt/C.

A fast and inexpensive strategy to fabricate ZnO–Cu composites as non-precious electrocatalysts for ethanol oxidation reaction in alkaline media

A fast and inexpensive strategy to fabricate ZnO–Cu composites as non-precious electrocatalysts for ethanol oxidation reaction in alkaline media

NiO nanocrystal anchored on pitaya peel-derived carbon laminated mesoporous composites for the electrocatalytic oxidation of ethanol

Direct ethanol fuel cell (DEFC) is a kind of energy conversion device with potential application prospect. The development of non-precious metal-based catalysts with high activity and stability is of great necessary for ethanol oxidation reaction (EOR). Here, the laminated composites with hollow structure were synthesized by a simple strategy, which consists of NiO nanocrystals anchored on pitaya peel-derived carbon (PPC). The electrochemical tests show that the optimal electrocatalyst (NiO@PPC-600) exhibits excellent catalytic activity for EOR with the current density (j) of 231.8 mA cm-2 (1.6 V vs. RHE) under alkaline conditions. Furthermore, the j retention rate (83.0%) of NiO@PPC-600 exceeds that (16.4%) of Pt/C in the long-term 12 h EOR test. The superior properties of the NiO@PPC-600 are mainly ascribed to its mesoporous structure that facilitates electrolyte and electron transfer and the PPC substrate that avoids the shedding of NiO nanocrystals, it has moderate lattice defects and graphitization, minimal contact resistance and Tafel slope. The work provides a simple route to prepare a high-efficient electrocatalyst for EOR, and the reuse of biomass pitaya peel (PP) is realized.

Ultrafine SnPd Nanoalloys Promise High-Efficiency Electrocatalysis for Ethanol Oxidation and Oxygen Reduction

The catalytic activity and stability of palladium (Pd)-based electrocatalysts for ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR) can be improved by optimizing their composition and structure. Alloying tin (Sn) into Pd can induce electronic and synergistic effects, which weaken the adsorption of intermediate species (e.g., O and OH in ORR and CO in EOR) on Pd sites and even promote their further transformation. However, the SnPd alloys often suffer from complicated synthesis, large particle size, and inhomogeneity. In this context, we report the synthesis of SnPd nanoalloys with an ultrafine size of ca. 3.8 nm using a simple one-pot approach and their superior catalytic performance for EOR and ORR. Specifically, the SnPd alloy nanoparticles with an optimized Sn/Pd ratio of 18/82 show the mass and specific activity of 3.8 A mg–1 and 5.72 mA cm–2, respectively, for EOR, while excellent performance for ORR with a half-wave potential of 0.92 V and specific activity of 3.46 mA cm–2 at 0.9 V, both of which are much higher than those of their commercial Pd/C and Pt/C counterparts.

ZIF-67-Derived NiCo-Layered Double Hydroxide@Carbon Nanotube Architectures with Hollow Nanocage Structures as Enhanced Electrocatalysts for Ethanol Oxidation Reaction.

The rational design of efficient Earth-abundant electrocatalysts for the ethanol oxidation reaction (EOR) is the key to developing direct ethanol fuel cells (DEFCs). Among these, the smart structure is highly demanded for highly efficient and stable non-precious electrocatalysts based on transition metals (such as Ni, Co, and Fe). In this work, high-performance NiCo-layered double hydroxide@carbon nanotube (NiCo-LDH@CNT) architectures with hollow nanocage structures as electrocatalysts for EOR were prepared via sacrificial ZIF-67 templates on CNTs. Comprehensive structural characterizations revealed that the as-synthesized NiCo-LDH@CNTs architecture displayed 3D hollow nanocages of NiCo-LDH and abundant interfacial structure between NiCo-LDH and CNTs, which could not only completely expose active sites by increasing the surface area but also facilitate the electron transfer during the electrocatalytic process, thus, improving EOR activity. Benefiting from the 3D hollow nanocages and interfacial structure fabricated by the sacrificial ZIF-67-templated method, the NiCo-LDH@CNTs-2.5% architecture exhibited enhanced electrocatalytic activity for ethanol oxidation compared to single-component NiCo-LDH, where the peak current density was 11.5 mA·cm-2, and the jf/jb value representing the resistance to catalyst poisoning was 1.72 in an alkaline environment. These results provide a new perspective on the fabrication of non-precious metal electrocatalysts for EOR in DEFCs.

Pt-Bi on carbon aerogels as efficient electrocatalysts for ethanol oxidation reaction in alkaline medium

Platinum-containing multimetallic catalysts supported on carbon materials have become one of the main choices for direct ethanol fuel cells (DEFCs) due to their high catalytic activity for the ethanol oxidation reaction (EOR). In this study, a platinum-bismuth alloy catalyst (PtBi@CA) with uniform distribution and small particles was provided by a one-step reduction method without the addition of structure directing agents and stabilizers. In the half-cell test, PtBi@CA(50−50) with the smallest crystallite size has high peak current density and pseudo-steady current density of 64.336 mA/cm2 and 0.096 mA/cm2, respectively, which is 11.22 times and 1.85 times the high of the most advanced commercial carbon-supported platinum catalysts (Pt/C). The method is simple and feasible, greatly reduces the amounts of precious metals, and has broad application prospects in the synthesis of anode electrocatalysts for direct ethanol fuel cells.

Activity and durability of intermetallic PdZn electrocatalyst for ethanol oxidation reaction

Activity and durability of intermetallic PdZn electrocatalyst for ethanol oxidation reaction

(Digital Presentation) Activated Carbon Supported Ni-Co Layered Double Hydroxides Nanowires: An Effective and Low-Cost Electrocatalyst Towards Ethanol Oxidation Reaction in Alkaline Media

Developing nanostructured architectures using non-noble, low-cost transition metals with good electrocatalytic activity and durability to replace noble electrocatalysts such as Pt and Pd have gained considerable attention in the field of sustainable and clean energy production technology. To address this, we adopted a facile synthesis route to synthesize Ni-Co layered double hydroxides (NiCo-LDH) nanowires supported on Activated Carbon (AC) via a one-pot hydrothermal synthesis method. The resulting NiCo-LDH nanowires, possessing a crystallite size of ~16.15 nm and a Surface area of 100.81 m2/g, have been utilized as a bifunctional electrocatalyst for ethanol oxidation reaction (EOR) in an alkaline medium. The electrochemical performance of the synthesized catalyst was investigated by Cyclic Voltammetry (CV), Chronoamperometry (CA), and Electrochemical Impedance Spectroscopy (EIS) techniques at room temperature. Impressively, NiCo-LDH/AC exhibited good electrocatalytic activity of 9.79 mA.cm-2 at 1.51 V vs. Saturated Calomel Electrode (SCE) and retained remarkable stability even after 200 cycles in 0.1 M NaOH with 1 M EtOH. The better electrocatalytic activity of NiCo/AC catalyst can be attributed to the presence of active sites and porous structures as well as the good electron transfer conductivity of AC. The attractive performance and facile synthesis of NiCo-LDH supported on AC highlights its potential application as an anodic material in direct ethanol fuel cells (DEFCs).

High C1 selectivity in alkaline ethanol oxidation reaction over stable Lewis pairs of Pd-MxC@CNT (M = W, Mo and Cr)

Pd-based catalysts have been widely studied as electrocatalysts for ethanol oxidation reaction (EOR) because of their higher oxygenophilic properties. However, there are still some disadvantages such as low activity, poor stability and poor selectivity, which hinder the development of EOR. Herein, a method through strong metal-support interaction (SMSI) and heterostructure of Pd-MxC@CNT (M = W, Mo and Cr) to construct a stable Lewis acid-base pair is proposed. Pd-W2C@CNT nanomaterial showed the highest mass activity (13.9 A mgPd−1), C1 selectivity (74.15%) and stability, better than Pd Black (3.5 A mgPd−1, 7.2%) and Pd@CNT (4.1 A mgPd−1, 7.6%). Ex situ and in situ electrochemical experiments reveal that the introduction of W2C became a stable electron donor for Pd, increasing the electron density of Pd atoms and forming a stable Lewis acidity Pd atoms to weaken the adsorption of intermediates. Reducing the electron density of W2C and forming a stable Lewis basicity W2C to provide sufficient OH adspecies for the reaction, thereby increasing the selectivity of the C1 pathway. Furthermore, the Pd-MxC@CNT synthesized by this method also exhibited excellent EOR activity, stability and C1 selectivity and glycerol oxidation reaction (GOR) performance.

Copper-doped nickel oxyhydroxide for efficient electrocatalytic ethanol oxidation

Rational design of low-cost and efficient electrocatalysts for ethanol oxidation reaction (EOR) is imperative for electrocatalytic ethanol fuel cells. In this work, we developed a copper-doped nickel oxyhydroxide (Cu-doped NiOOH) catalyst via in situ electrochemical reconstruction of a NiCu alloy. The introduction of Cu dopants increases the specific surface area and more defect sites, as well as forms high-valence Ni sites. The Cu-doped NiOOH electrocatalyst exhibited an excellent EOR performance with a peak current density of 227 mA·cm−2 at 1.72 V versus reversible hydrogen electrode, high Faradic efficiencies for acetate production (> 98%), and excellent electrochemical stability. Our work suggests an attractive route of designing non-noble metal based electrocatalysts for ethanol oxidation.

Preparation of graphite carbon/Prussian blue analogue/palladium (GC/PBA/pd) synergistic-effect electrocatalyst with high activity for ethanol oxidation reaction

In this paper, newly graphite carbon/Prussian blue analogue/palladium (GC/PBA/Pd) synergistic-effect electrocatalyst for ethanol oxidation reaction were developed, with Co-based PBA (Co3[Co(CN)6]2) as a co-catalyst. Structural analysis shows that the Co3(Co(CN)6)2 nanoparticles were highly dispersed and inlaid on surface of GC nanosheets with outstanding structural stability. The GC/Co3(Co(CN)6)2/Pd electrocatalyst exhibits significantly enhanced electrocatalytic activity towards ethanol oxidation with a maximum mass activity of 2644 A g−1 Pd GC/Pd, which is more than double that of GC/Pd electrocatalyst (1249 A g−1). Excellent electrochemical stability is also demonstrated for this GC/Co3(Co(CN)6)2/Pd electrocatalyst. The enhanced electrocatalytic activity can be attributed to the synergistic effects of GC support and Co3(Co(CN)6)2 promoter on the Pd electrocatalysts, in which Co3(Co(CN)6)2 acts as a co-catalyst and GC acts as a conductive support.