Electrocatalysts For Ethanol Electro-oxidation Research Articles

Mild Synthesis of Planar PdPtAuAgCuIr Nanocrystals with Granular Edges for Improved Ethanol Electrooxidation

AbstractWe report a mild, one‐pot synthesis of PdPtAuAgCuIr multimetallic nanocrystals with controlled shapes and explore their applications as the electrocatalysts for ethanol electrooxidation in alkaline medium. The success of current synthesis relies on the co‐reduction of six metal precursors in the presence of octadecylammonium chloride and ascorbic acid at an elevated temperature. The resulting products are featured with an in‐plane core‐shell structure, together with the trigonal/hexagonal plate decorated with granular edges. When serving as EOR electrocatalysts, the carbon‐supported PdPtAuAgCuIr nanocrystals exhibit more than five‐fold increase in mass activity as compared to that of commercial Pt/C, as well as improved reaction kinetics and long‐term durability. DFT calculations disclose that the reduced energy barrier renders the Pd‐based multimetallic catalyst in catalytic performance. The present study provides a feasible strategy to create multimetallic nanocrystals with controlled two‐dimensional morphology under ambient conditions, shedding light for rational design over advanced fuel cell catalysts composed of multimetallic alloy.

Trimetallic PdRhPt Porous Nanooctahedra as Highly Active and Cost‐Effective Electrocatalysts for Ethanol Electrooxidation

AbstractThe development of highly active and cost‐effective electrocatalysts for the ethanol oxidation reaction (EOR) is imperative for the prospective application of direct ethanol fuel cells (DEFCs). In this study, we successfully synthesized porous octahedral nanoarchitectures comprising Pd, Rh, and Pt, through a straightforward one‐step co‐reduction aided by additional Ag precursors and other surface capping agents. The in‐situ galvanic replacement played a pivotal role in shaping hollow structures within the prepared PdRhPt porous octahedra, designated as PdRhPt‐POct. By strategically employing both composition and structure engineering, PdRhPt‐POct exhibited remarkably enhanced activity and stability toward EOR. Specifically, the mass activity of PdRhPt‐POct, reaching 8.11 A mg−1Pd+Pt, surpassed that of the majority of state‐of‐the‐art EOR electrocatalysts, owing to increased efficiency in C−C bond breaking and enhanced anti‐poisoning properties. This work introduces new prospects for designing and producing unique hollow‐structured multi‐metal nanocrystals as high‐performance EOR catalysts.

Tailored synthesis and optimization of nickel-molybdenum carbide-graphite nanofiber composite for enhanced ethanol electrooxidation.

A novel nickel-molybdenum carbide-graphite nanofiber composite is introduced as an electrocatalyst for ethanol electrooxidation. The proposed nanofibers have been prepared by calcinating electrospun nanofibers composed of nickel acetate tetrahydrate, molybdenum chloride, and polyvinyl alcohol. The calcination process was conducted at different temperatures (700, 850, and 1000°C) under a nitrogen gas atmosphere with a heating rate of 2.5 deg/min and a holding time of 5 h. Physicochemical characterizations have indicated that nickel acetate is entirely reduced to nickel metal during the sintering process, and molybdenum has bonded with carbon to produce molybdenum carbide. At the same time, the used polymer has been pyrolyzed to produce a carbon nanofiber matrix embedding formed inorganic nanoparticles. Electrochemical measurements concluded that molybdenum content and calcination temperature should be controlled to maximize the electrocatalytic activity of the proposed catalyst. Typically, the oxidation peak current density was 28.5, 28.8, 51.5, 128.3, 25.6, and 3 mA/cm2 for nanofibers prepared from an electrospun solution containing 0, 5, 10, 15, 25, and 35 wt% molybdenum carbide, respectively. Moreover, it was observed that increasing the calcination temperature distinctly improves the electrocatalytic activity. Kinetic studies have indicated that the reaction order is close to zero with a reaction temperature-dependent value. Moreover, it was detected that the electrooxidation reaction of ethanol over the proposed nanofiber composite follows the Arrhenius equation. The determined activation energy is 33 kJ/mol, which indicates good catalytic activity for the introduced nanofibers. Through the application of a set of visualization-based tools and the general linear model (GLM), the optimal conditions that generate the highest current density were identified. The computations unveiled that the optimal parameter settings are as follows: Mo content at 15 wt.%, methanol concentration of 1.55 M, and reaction temperature of 59°C.

Synthesis of nitrogen and phosphorus co-doped graphene quantum dots as metal-free electrocatalysts for ethanol electrooxidation

In this study, three electrocatalysts containing graphene quantum dots, nitrogen-doped graphene quantum dots, and nitrogen and phosphorus co-doped graphene quantum dots are successfully synthesized by a simple hydrothermal method. The as-prepared electrocatalysts are characterized using spectroscopic and electrochemical techniques. The results confirm a uniform distribution and a high order structure with a nanoparticle size of 1–3 nm for all electrocatalysts. Electrochemical analysis demonstrates that the as-synthesized nitrogen and phosphorus co-doped graphene quantum dots (16.67 A g−1) exhibit improved catalytic activity towards ethanol oxidation reaction in alkaline media as compared to nitrogen-doped graphene quantum dots (6.903 A g−1) and graphene quantum dots (0.139 A g−1). Moreover, the nitrogen and phosphorus co-doped graphene quantum dots display a low overpotential than two other synthesized catalysts. The enhanced electrochemical performance may be related to the synergetic effect of phosphorous addition on the nitrogen-doped graphene quantum dots. Based on the results, as-prepared phosphorus and nitrogen co-doped graphene quantum dots could be a promising anodic catalyst for the direct ethanol fuel cells application.

Self-assembled platinum-tungsten carbide (Pt-WC)/multi-walled carbon nanotubes (MWCNTs) electrocatalysts for ethanol electro-oxidation in acid medium

The design of a high-performance, durable and low-cost catalyst for direct ethanol fuel cells (DEFCs) applications is an eternal pursuit for researchers in the materials field. In this work, a kind of novel platinum-tungsten carbide (Pt-WC)/multi-walled carbon nanotubes (MWCNTs) electrocatalyst with different WC loadingsis prepared by self-assembly technology for ethanol oxidation reaction (EOR). The electrochemical performance and stability of Pt-WC/MWCNTs electrocatalysts toward EOR are investigated by cyclic voltammetry and chronoamperometry. The mass activity of Pt-WC0.15/MWCNTs electrocatalyst for EOR is 581.94 mA mg-1Pt, which is 1.33 times higher than that of commercial Pt/C (ETEK). The significant enhancement can be attributed to the more exposed active sites and the synergistic effect between Pt and WC. The Pt-WCx/MWCNTs are a kind of excellent and effective electrocatalyst for EOR, which has a broad application prospect in fuel cells.

Electrodeposition of ternary CuNiPt alloy nanoparticles on graphenized pencil lead electrode as a new electrocatalyst for electro-oxidation of ethanol

In the present study, the ternary CuNiPt alloy nanoparticles (CuNiPt-ANPs) were electrodeposited on the graphenized pencil lead electrode (GPLE) surface, and the obtained modified electrode (CuNiPt-ANPs/GPLE) was examined as a new electrocatalyst towards ethanol electro-oxidation reaction (EEOR). The GPLE was fabricated through the electrochemical exfoliation of pencil lead electrode (PLE) in acidic condition on a three-electrode electrochemical cell. The physicochemical and electrocatalytic characterizations of the prepared electrocatalyst were examined by means of various techniques: X-ray powder diffraction spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, elemental mapping analysis, cyclic voltammetry, and chronoamperometry. Comparison of the electrocatalytic activity of the introduced electrocatalysts (PtNPs/PLE, PtNPs/GPLE, CuPt-ANPs/GPLE, NiPt-ANPs/GPLE, and CuNiPt-ANPs/GPLE) showed that the CuNiPt-ANPs/GPLE has the highest and good electrocatalytic activity (first anodic peak current density = 101 mA cm−2) and outstanding stability for the EEOR in acidic media. This work offers not only an easy and efficient synthesis strategy but also opens new avenues for the design of high performance promising electrocatalyst for fuel cell systems.

A metal–organic framework derived PtCo/C electrocatalyst for ethanol electro-oxidation

Abstract Currently, designing and preparing low-cost and high-efficiency electrocatalysts still remains of huge impediment for direct ethanol fuel cells (DEFCs). In this work, by leveraging the unique superiority of Co3[Co(CN)6]2 (Prussian blue analogues, PBA) precursor, we used Pt4+ to replace partial dispersed Co2+ in Co3[Co(CN)6]2 and a metal–organic framework (MOF) derived PtCo electrocatalyst (MD-PtCo/C) was successfully fabricated. Notably, as-obtained MD-PtCo/C (Pt, 0.9532 wt.%) electrocatalyst achieves high utilization rate of ultra-low Pt load and exhibits favorable electrocatalytic performance with lower onset potential, higher EOR activity, less activation energy (Ea) value and better stability compared to commercial Pt/C for ethanol oxidation reaction (EOR). Moreover, the consequence of concentrations (KOH, C2H5OH) and temperatures on electrocatalytic activity of EOR have also been studied. This study would be supportive of developing highly active and low-cost electrocatalysts for other catalytic applications.

Effect of Heat Treatment and Bath Compositions on the Performance of Co-Ni-Mo-P Electrocatalysts for Ethanol Electro-Oxidation

As-deposited (ASD) Co-Ni-Mo-P electrocatalyst on carbon support was investigated for the ethanol electro-oxidation. Electrocatalysts were prepared by electroless deposition method on carbon substrate support (CCS) made active for electroless deposition with Pd-ink. The reaction performances for all electrodes were investigated using cyclic voltammetry (CV). An effect of electroless bath compositions was studied. The result showed that the current density tended to increase with increasing Co, Ni, and Mo contents, suggesting that they contributed to the catalytic activity. The optimum molar ratio of NiSO4, CoSO4, and Na2MoO4 was 1:1.8:0.6 for the catalyst without heat treatment. In addition, after the electrocatalysts were treated thermally for 2h under H2/Ar gas at different temperatures, an optimal temperature of 400°C was identified for which the current density was higher than any other annealing temperature including that of the ASD electrocatalyst. The result is attributed to the effect of crystallinity and particle sizes. Above and below this optimal temperature, the current density decreased, indicating that the crystalline structures at these conditions are not appropriate for optimal performance. Moreover, the active surface area decreased after the heat treatment because the catalyst lost its amorphous structure. Additionally, the stability of the ASD and thermally treated electrocatalysts will be discussed. Figure 1

Tin oxide species as promotive additives to Ni-P/C electrocatalysts for ethanol electro-oxidation in NaOH solution

Incorporating transition metal oxide species in the chemical structure of nickel-based electrocatalysts was beneficial in improving their activity as anode materials in fuel cells. Electroless deposition technique was employed to synthesize Ni-P-SnO2/C composites containing variable wt% values of tin oxide species. Scanning electron micrographs revealed spherical nickel particles with diameter values ranging between 500 and 1100 nm. Elemental mapping images of these composites confirmed the presence of nickel, phosphorous, tin, oxygen and carbon in their structural composition. An enhanced performance of these Ni-P-SnO2/C electrocatalysts was measured during ethanol oxidation reaction in alkaline solution. The added SnO2 content in the prepared electrocatalysts was found to influence their electrocatalytic activity. The highest ethanol oxidation current density values were attained at electrocatalysts containing 2.5 or 25 wt% SnO2. Furthermore, chronoamperometry demonstrated their stable behavior over prolonged operation. The charge transfer properties of Ni-P-SnO2/C electrocatalysts were significantly affected by the chosen potential value, ethanol and NaOH concentrations.

Improved Pt/CeO2 Electrocatalysts for Ethanol Electro-oxidation

Improved Pt/CeO2 Electrocatalysts for Ethanol Electro-oxidation

Sonochemical synthesis of high-performance Pd@CuNWs/MWCNTs-CH electrocatalyst by galvanic replacement toward ethanol oxidation in alkaline media

In this paper, a fast and effective method for the palladium (Pd) wire nanostructures synthesis with the great surface area through galvanic replacement reaction utilizing copper nanowires (CuNWS) as a template by the assistance of ultrasound under room temperature condition is proposed. A multifunctional catalyst with the mentioned nanostructure, Pd@CuNWs, and multi walled carbon nanotubes (MWCNTs) and chitosan (CH) as a binder was fabricated. To investigate the morphology and bulk composition of the prepared catalyst, Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Powder Diffraction (XRD), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) were utilized. Various electrochemical techniques including chronoamperometry and cyclic voltammetry were employed for the electrocatalytic activity of ethanol electrooxidation and durability in basic solution. Electrochemical catalytic activity and durability evaluation results proved that the as-synthesized Pd@CuNWs/MWCNTs-CH has a super electrocatalytic activity compared to Pd/MWCNTs and Pd/C electrocatalysts for ethanol electrooxidation. Pd@CuNWs/MWCNTs-CH catalyst demonstrated substantially enhanced performance and long-term stability for ethanol electrooxidation in the basic solution in comparison to Pd/MWCNTs and commercial Pd/C demonstrated the potential in utilizing Pd@CuNWs/MWCNTs-CH as an efficient catalyst for ethanol oxidation. Additionally, thermodynamic and kinetic evaluations revealed that the Pd@CuNWs/MWCNTs-CH catalyst has lower activation energy compared to Pd/MWCNTs and Pd/C which leads to a lower energy barrier and an excellent charge transfer rate towards ethanol oxidation. Noticeably, the Pd@CuNWs/MWCNTs-CH presented excellent catalytic activities with high peak current density which was 9.5 times more than Pd/C, and more negative onset potential in comparison to Pd/C is acquired for ethanol electrooxidation denoting synergistic effect between CuNWs/MWCNs-CH and Pd. The Pd@CuNWs/MWCNTs-CH can be considered as a valid candidate among available electrocatalysts in direct ethanol fuel cells (DEFCs).

Pd-NiO decorated multiwalled carbon nanotubes supported on reduced graphene oxide as an efficient electrocatalyst for ethanol oxidation in alkaline medium

The synthesis of Pd-NiO nanoparticles decorated multiwalled carbon nanotubes (MWCNTs) on reduced graphene oxide (rGO) for ethanol electrooxidation is reported. NiO nanoparticles (NPs) were deposited on functionalized MWCNTs by wet impregnation method. Pd nanoparticles were formed on NiO-MWCNTs by the addition of PdCl2 and its reduction using NaBH4. The Pd-NiO/MWCNTs nanocomposite then deposited on rGO support using ultrasound irradiation which led to the formation of the Pd-NiO/MWCNTs/rGO electrocatalyst. The prepared electrocatalysts were characterized by XRD, SEM, HR-TEM and XPS analysis. Electrochemical measurements demonstrate that as synthesized Pd-NiO/MWCNTs/rGO electrocatalyst exhibit higher catalytic activity (90.89 mA/cm2) than either Pd/MWCNTs/rGO (43.05 mA/cm2) or Pd/C (28.0 mA/cm2) commercial catalyst. Chronoamperometry study of Pd-NiO/MWCNTs/rGO electrocatalyst showed long-term electrochemical stability. The enhanced catalytic activity of Pd-NiO/MWCNTs/rGO electrocatalyst for electrooxidation of ethanol can be attributed to the synergistic effect between Pd & NiO active sites.

Simple room temperature synthesis of porous nickel phosphate foams for electrocatalytic ethanol oxidation

The simple and eco-friendly fabrication of non-noble metal catalyst is of great importance for sustainable energy production from alcohol. Herein, we report the new synthetic route for the preparation of nickel phosphate nanostructure through simple co-precipitation method. We studied the effect of annealing temperature ranging from 500°C to 1100°C on the electrocatalyst for ethanol electro-oxidation. In addition, we demonstrate that the resulting nickel phosphate materials can serve as efficient transition metal electrocatalyst for the ethanol oxidation under alkaline condition. In particular, the nickel phosphate annealed at 900°C (NP-900) affords higher current density of 1.2mAcm−2 at the low potential of 0.7mV, demonstrating great catalytic stability as well as good cyclability for 1000cycles giving about 92% faradaic yield towards the ethanol.

Palladium modified gold nanoparticles as electrocatalysts for ethanol electrooxidation

Resemblin, g core-shell electrocatalysts consisting of a Au core and Pd shell (Au@Pd) are synthesized via a Cu underpotential deposition (UPD)-Pd-displacement method. The Pd shell is non-uniform consisting of tiny Pd clusters with a coverage of 0.5–0.6. The ethanol oxidation reaction (EOR) activity of this kind of structure is much higher than Pd/C in an alkaline solution. The forward peak current density of Au@Pd is 5.4 times higher than that of Pd/C. Furthermore, the onset potential for EOR of the former is ∼100 mV more negative. An interesting particle size dependent EOR activity is also observed. With increasing the Au particle size (2.9, 5.8 and 6.5 nm), the EOR activity increases. The strain and ligand effects from the Au core, together with the bifunctional reaction mechanism in the Au–Pd system may be reasons for the enhanced activity in Au@Pd catalysts.

Influence of the support on PtSn electrocatalysts behavior: Ethanol electro-oxidation performance and in-situ ATR-FTIRS studies

Different activated biocarbons (aBCs) were prepared from Eucalyptus grandis wood and activated Vulcan carbons (aVCs) were prepared from commercial Vulcan XC72 carbon. These carbon materials were used as a support in a PtSn/C electrocatalysts for ethanol electro-oxidation (EEO). Structural, morphological and chemical composition differences of the electrocatalysts were correlated to their electrocatalytic performance, and by in-situ Fourier Transform Infrared Spectroscopy in the Attenuated Total Reflectance mode (in-situ ATR-FTIRS), with the ethanol electro-oxidation mechanism (EEOM) pathways and product distributions at different potentials using sulfuric acid as a base electrolyte.The nature of the carbon support and it activation method affected the morphological and structural characteristics of the PtSn based electrocatalysts. The electrocatalytic performance of the electrocatalysts supported on the aBCs was better than that of the supported on the activated Vulcan carbons. The PtSn electrocatalysts using CO2 activated biocarbon support had a higher electrochemically active surface area (EASA), lower onset potential and greater current density for the EEO. It was determined that the EEO on all studied PtSn electrocatalysts in sulfuric acid media occurs mainly through the acetic acid and acetaldehyde production.

Facile and shape-controlled electrochemical synthesis of gold nanocrystals by changing water contents in deep eutectic solvents and their electrocatalytic activity

Au NCs with different morphologies were synthesized in DESs by changing water contents, and used as electrocatalysts for ethanol electrooxidation.

Synthesis and enhanced electrocatalytic properties of Au/Pd/Pt nanohollows

Well-defined hollow Au/Pd/Pt nanoparticles (NPs) were synthesized through a two-step galvanic replacement reaction, which were used as the electrocatalysts for ethanol electrooxidation under alkaline conditions. The Au/Pd/Pt nanohollows (NHs) showed remarkably enhanced catalytic property in comparison with those of the Pd NPs and Au/Pd NHs. Moreover, the electrcatalytic properties of the Au/Pd/Pt NHs were closely dependent on their Pt contents. With increasing the Pt contents, the electrochemical properties of the Au/Pd/Pt NHs gradually enhanced and then lowered. Our results indicated that the Au/Pd/Pt NHs prepared using 22.5µL H2PtCl6 possessed the most excellent electrochemical properties in comparison with Au/Pd, Pd/Pt, Au/Pt and other Au/Pd/Pt nanocatalysts.

Deoxyribonucleic acid-directed growth of well dispersed nickel–palladium–platinum nanoclusters on graphene as an efficient catalyst for ethanol electrooxidation

Trimetallic NiPdPt alloy nanoclusters with diameter of about 10 nm are successfully dispersed on the deoxyribonucleic acid-modified reduced graphene oxide (DNA-rGO) by using NaBH4 as reductant. The prepared NiPdPt nanoclusters grown on DNA-rGO (NiPdPt/DNA-rGO) composite are used as electrocatalysts for ethanol electrooxidation in alkaline solution. Cyclic voltammetry and chronoamperometry are used to investigate the electrochemical activities and stabilities of the catalysts. The Ni1Pd1Pt1/DNA-rGO (molar ratio of Ni, Pd, Pt is 1:1:1) has extraordinary electrocataltic activity, with their mass current density reaching 3.4 A mg−1metal and better stability. As compared with the bimetallic counterparts and NiPdPt grown on multi-wall carbon nanotubes, Ni1Pd1Pt1/DNA-rGO retains the highest mass current density after a 2000 s current-time test at 0 V.

Pulse electrodeposited Ni-Gd2O3 nanocomposite electrode as electrocatalysts for ethanol electro-oxidation

In this work, pure Ni and Ni-Gd2O3 nanocomposites are deposited on mild steel surface using nickel sulphamate electrolyte by pulse electrodeposition method. The effect of Gd2O3 nano particles concentration on the preferred orientation of Ni-Gd2O3 nanocomposite was studied by X-ray diffractrometer. The surface morphology, surface topography and chemical composition of deposited pure Ni and Ni-Gd2O3 nanocomposite was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDAX) respectively. The electrocatalytic activity of the pure Ni and Ni-Gd2O3 nanocomposite electrodes for the electro-oxidation of ethanol was studied by cyclic voltammetry and chronoamperometry. The results showed that, Ni-Gd2O3 nanocomposite electrode increases the electrocatalytic activity towards ethanol electro-oxidation compared with pure Ni. However, the chronoamperometry experiments revealed that the stability of the Ni-Gd2O3 composite electrodes with time is found to be equivalent to pure Ni electrode.

Electrochemical and Fuel Cell Evaluation of PtIr/C Electrocatalysts for Ethanol Electrooxidation in Alkaline Medium

PtIr/C electrocatalysts prepared by borohydride reduction process were characterized by X-ray diffraction, transmission electron microscopy, and cyclic voltammetry. The X-ray diffraction measurements suggested the PtIr alloy formation; furthermore, peaks of IrO2 were not observed; nevertheless, the presence of Ir oxides in small amounts and amorphous forms cannot be discarded. The transmission electron microscopy showed the average particle diameter between 4.0 and 6.0 nm for all compositions prepared. The catalytic activity for ethanol electrooxidation in alkaline medium at room temperature (cyclic voltammetry and chronoamperometry results) showed that PtIr/C (70:30) and PtIr (90:10) exhibited higher performance toward ethanol oxidation than the other electrocatalysts. Experiments using direct ethanol alkaline fuel cell at 75 °C showed PtIr (90:10) as the best electrocatalyst and Ir/C as virtually inactive for ethanol oxidation in real conditions. The best result obtained using PtIr/C may be associated to the electronic effect between Pt and Ir that could decrease the poisoning on catalyst surface and also by the occurrence of bifunctional mechanism.