Activity For Ethanol Oxidation Reaction Research Articles

On the design of Pt-Sn efficient catalyst for carbon monoxide and ethanol oxidation in acid and alkaline media

Pt-Sn catalysts supported on carbon, with different Pt-Sn atomic ratios (3:1, 1:1, 1:3), were prepared through the formic acid method (FAM) and supported on different carbon supports (nanofibers and carbon blacks) to study their behavior toward CO stripping and ethanol oxidation reaction (EOR). PtSn/C catalysts and supports were physicochemically characterized by XRD, EDX, XPS, TEM and TPD. Good particle dispersion onto the carbon support, similar particle sizes (around 4–5nm) and the presence of tin oxides were observed in all cases. Sn insertion favored the development of the Pt3Sn1 phase and the presence of higher oxidation states of both metals in the catalyst. Ethanol and adsorbed CO oxidation were studied at these materials both in acid and alkaline media, by linear sweep voltammetry and chronoamperometry. Higher EOR current densities were obtained with the increase in the amount of Sn in the samples, been those materials supported on CNF the ones with the best CO tolerance and catalytic activity toward this reaction. As expected, a great improvement of the EOR activity was found in alkaline media compared to sulfuric acid media, providing good expectative for these materials as catalysts for alkaline direct ethanol fuel cells.

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.

Carbon Supported Oxide-Rich Pd-Cu Bimetallic Electrocatalysts for Ethanol Electrooxidation in Alkaline Media Enhanced by Cu/CuOx

Different proportions of oxide-rich PdCu/C nanoparticle catalysts were prepared by the NaBH4 reduction method, and their compositions were tuned by the molar ratios of the metal precursors. Among them, oxide-rich Pd0.9Cu0.1/C (Pd:Cu = 9:1, metal atomic ratio) exhibits the highest electrocatalytic activity for ethanol oxidation reaction (EOR) in alkaline media. X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) confirmed the existence of both Cu and CuOx in the as-prepared Pd0.9Cu0.1/C. About 74% of the Cu atoms are in their oxide form (CuO or Cu2O). Besides the synergistic effect of Cu, CuOx existed in the Pd-Cu bimetallic nanoparticles works as a promoter for the EOR. The decreased Pd 3d electron density disclosed by XPS is ascribed to the formation of CuOx and the spill-over of oxygen-containing species from CuOx to Pd. The low Pd 3d electron density will decrease the adsorption of CH3COads intermediates. As a result, the electrocatalytic activity is enhanced. The onset potential of oxide-rich Pd0.9Cu0.1/C is negative shifted 150 mV compared to Pd/C. The oxide-rich Pd0.9Cu0.1/C also exhibited high stability, which indicated that it is a candidate for the anode of direct ethanol fuel cells (DEFCs).

Double layer effects in electrocatalysis: The oxygen reduction reaction and ethanol oxidation reaction on Au(1 1 1), Pt(1 1 1) and Ir(1 1 1) in alkaline media containing Na and Li cations

Oxygen reduction and ethanol oxidation reactions were studied on Au(111), Pt(111) and Ir(111) in alkaline solutions containing sodium and/or lithium cations. By keeping the same (111) surface orientation and exploring oxophilicity trends and non-covalent interactions between OHad and alkali metal cations (AMCn+), we were able to gain deep insights into the multiple roles that OHad plays in these important electrocatalytic reactions. Cyclic voltammetry experiments revealed that OHad formation initiates at distinct electrode potentials, governed by the oxophilicity of the specific metal surface, with further OHad adlayer stabilization by non-covalent alkali-cation interactions and affecting the formation of a “true oxide” layer at higher electrode potentials. Although OHad is a simple spectator for the ORR, it promotes the ethanol oxidation reaction (EOR) at lower potentials and act as spectator at high OHad coverages. By changing the alkali metal cation at the interface (Li+) on more oxophilic surfaces, it was possible to promote the EOR even more, relative to Na+, without changing the product distribution for the reaction. This cation effect suggests that OHad–Li+(H2O)x clusters can stabilize the ethoxide adlayer, thus improving the EOR activity. Our results indicate the importance of the entire electrochemical interface in determining the electrocatalytic activity during reaction.

Structure-Controlled Rh/Sn/Pt Ternary Catalysts for Complete Oxidation Reaction of Ethanol to Carbon Dioxide

Sn was deposited on a Pt electrode (Sn/Pt) with the coverage of 0.23, following by the Rh deposition by different methods: random arrangement (Rh/Sn/Pt(1)) and controlled arrangement (Rh/Sn/Pt(2)). Inductive coupled plasma mass spectroscopy (ICP-MS) was used to evaluate the Sn/Rh molar ratio, which was 3 for Rh/Sn/Pt(1) and 6 for Rh/Sn/Pt(2). The ethanol oxidation reaction (EOR) activity of Rh/Sn/Pt(2) was similar to that of Sn/Pt, which was ca. 3 times as high as that of Pt. However, the EOR activity of Rh/Sn/Pt(1) was ca. 1.5 times as high as that of Sn/Pt. The onset potential of EOR for the Sn/Pt and Rh/Sn/Pt electrodes was 0.1 V and 0.2 V lower than that for the Pt electrode, respectively. The in-situ infrared reflection absorption spectroscopy (IRRAS) exhibited that, for Rh/Sn/Pt(1), the formation of acetic acid was predominant over CO2, whereas Rh/Sn/Pt(2) with lower EOR activity was superior in CO2 selectivity to Rh/Sn/Pt(1).

Multi-walled carbon nanotubes supported Pd composite nanoparticles hydrothermally produced from technical grade PdO precursor

Palladium (Pd) composite nanoparticles (NPs) supported on multi-walled carbon nanotubes (MWCNTs) (denoted as Pd/MWCNTs) are fabricated by a very simple process of hydrothermal reaction (HR) using the technical grade PdO as the precursor. With a HR period of 3h, the Pd NPs with an average size of ∼5.0nm are found to be quite uniformly dispersed on the surface of MWCNTs. The electrocatalytic activity towards ethanol oxidation reaction (EOR) for the synthesized catalysts is probed by using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The 3-h prepared catalyst has demonstrated 6.7 times better EOR activity than 5-h prepared sample (159.7mAmg−1vs. 23.8mAmg−1) at an applied potential of −0.24V (vs. SCE) in the CA test. The excellent electrocatalytic activity of the 3-h Pd/MWCNTs catalyst toward EOR is mainly ascribed to its easier hydrogen evolution, lower electrode potential and the existence of PdO as compared to other catalysts prepared.

Multiwalled Cabon Nanotubes Functionalized Magnetic Fepd Alloy with Enhanced Activity for Ethanol Oxidation Reaction

Ultrafine Palladium iron alloy (FePd) nanoparticles (NPs) deposited on gamma phased iron oxide (r-Fe2O3), FePd-Fe2O3, which were further anchored on Multi-walled carbon nanotubes (MWNTs), FePd-Fe2O3/MWNTs, was successfully synthesized by a facile one-pot solution based method as thermal decomposing palladium acetylacetonate (Pd(acac)2) and iron pentacarbonyl (Fe(CO)5) in a refluxing dimethylformamide (DMF) solution in the presence of carboxylic groups functionalized MWNTs (MWNTs-COOH). The formation of FePd alloy was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) through investigating the crystalline structures and verifying specific bonding energy. Transmission electron microscope (TEM) revealed that the ultrafine FePd NPs were uniformly deposited on the surface of superparamagnetic r-Fe2O3 NPs which were further evenly distributed on the MWNTs surface. A 3.65 increase of peak current density after normalizing to Pd mass was observed in cyclic voltammetry (CV) for ethanol oxidation reaction compared with that of Pd/MWNTs. Greatly enhanced tolerance stability towards poisoning species and largely reduced charge resistances were also obtained in chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) due to the formation of FePd alloy and the unique double deposited Pd structure. Experimental 100.0 mg MWNTs-COOH was first dispersed in 60 mL DMF solution undergoing 1h sonication, the solution was then transferred to a 250-mL 3-neck flask and heated to reflux (~160 °C) in ~ 20 min. For the synthesis of FePd-based nanocatalysts, 202.0 mg well dispersed Pd(acac)2 in 20 mL DMF was added to the refluxing MWNTs-COOH/DMF solution. Fe(CO)5 (130.2, 437.0, and 875.0 mg) was following added to the solution after boiling again in ~ 5 min, the products were donated as FePd-Fe3C/MWNTs, FePd-Fe2O3(3:5)/MWNTs and FePd-Fe2O3(3:10)/MWNTs, respectively(the composition was determined by Mössbauer spectrometer). For the control synthesis of Pd/MWNTs and Fe3O4/MWNTs, only 202.0 mg Pd(acac)2 or 875.0 mg Fe(CO)5 was added to the refluxing MWNTs-COOH/DMF solution. All the solutions were maintained refluxing for an additional 3 hours to complete the whole reaction. Finally, after cooling down to room temperature, the solid iron containing products were removed from the suspension using a permanent magnet and Pd/MWNTs were filtered under vacuum. All the final products were rinsed with acetone 3 times and collected after vacuum drying at 60 °C for 24 hours. Results and Discussion The Mössbauer spectrometer and XPS has successfully determined the compositions of catalysts with varying the amount of Fe(CO)5. Typical peaks of Fe2O3, Fe3O4 and FePd are clearly observed in XRD indicating the successful synthesis of FePd-Fe2O3/MWNTs. The interaction between NPs and MWNTs and the loading of catalysts was determined by Raman spectra and TGA. An greatly enhanced the peak current in CV and improved tolerance stability toward poisoning species are also demonstrated by CV, CV and EIS, which indicates the positive role of the FePd alloy and the Fe2O3 substrates. Conclusion Highly catalytic active and magnetic FePd-Fe2O3/MWNTs nanocatalysts have been prepared by simple thermal decomposing Pd(acac)2 and Fe(CO)5 in a refluxing dimethylformamide (DMF) solution in the presence of MWNTs-COOH. The formation of FePd alloy has been confirmed by the crystalline structures and composition investigation by XRD and XPS spectra. A unique structure as FePd NPs first deposited on Fe2O3 NPs which further uniformly dispersed on MWNTs was disclosed by TEM. Electro-characterizations as CV, CA and EIS demonstrated an enhanced catalytic performance compared with Pd/MWNTs towards EOR after the introduction of Fe. Modified electronic properties of Pd by Fe, easily proceeded poisoning species on γ-Fe2O3 and the optimal combination of promoter Fe2O3 and MWNTs substrate are mainly account for the greatly enhanced activity. This simple method is of great significance for the facile preparation of recyclable Pd catalysts with high catalytic activity. Acknowledgments The financial supports from University of Tennessee Knoxville are kindly acknowledged. Figure 1. CV of (a) Fe3O4/MWNTs, (b) Pd/MWNTs, (c) FePd-Fe2O3(3:10)/MWNTs, (d) FePd-Fe3C/MWNTs and (e) FePd-Fe2O3(3:5)/MWNTs in 1.0 M KOH solution containing 1.0 M ethanol with current density normalized to Pd mass at a scan rate of 50 mV/s. Background is the HRTEM of FePd-Fe2O3(3:5)/MWNTs. References 1 Y. Wang, Q. He, J. Guo, H. Wei, K. Ding et al, ChemElectroChem, 2(4) (2015) 559-570. 2. Z. Zhang, J. Ge, L. Ma, J. Liao, T. Lu, W. Xing, Fuel Cells, 9 (2) (2009) 114-120 Figure 1

Trimetallic PtSnRh Wavy Nanowires as Efficient Nanoelectrocatalysts for Alcohol Electrooxidation.

The design and creation of efficient catalysts for alcohol oxidation reaction has attracted great research attention because alcohols are promising fuels for direct fuel cell reactions because of their high energy density, easy storage, and transportation. We herein report an efficient strategy that allows the preparation of ternary PtSnM (M=Co, Ni, and Rh) wavy nanowires (WNWs) with ultrathin diameter of only around 2 nm and tunable compositions in high yield. Detailed catalytic studies show that all the ternary WNWs exhibit high performance for ethanol oxidation reaction (EOR) and methanol oxidation reaction (MOR), and their performance shows interesting composition-dependent electrocatalytic activity with PtSnRh WNWs having the best activity for both EOR and MOR. The PtSnRh WNWs are also more stable than commercial Pt/C catalyst, as revealed by long-time chronoamperometric (CA) measurements. The present work highlights the use of multimetallic WNWs as highly active and durable nanocatalysts in enhancing alcohol electrooxidation, which will open a new way in tuning 1D multimetallic nanostructures for boosting other fuel cell reactions, various heterogeneous reactions, and beyond.

Improving the Ethanol Oxidation Activity of Pt-Mn Alloys through the Use of Additives during Deposition

In this work, sodium citrate (SC) was used as an additive to control the particle size and dispersion of Pt-Mn alloy nanoparticles deposited on a carbon support. SC was chosen, since it was the only additive tested that did not prevent Mn from co-depositing with Pt. The influence of solution pH during deposition and post-deposition heat treatment on the physical and electrochemical properties of the Pt-Mn alloy was examined. It was determined that careful control over pH is required, since above a pH of four, metal deposition was suppressed. Below pH 4, the presence of sodium citrate reduced the particle size and improved the particle dispersion. This also resulted in larger electrochemically-active surface areas and greater activity towards the ethanol oxidation reaction (EOR). Heat treatment of catalysts prepared using the SC additive led to a significant enhancement in EOR activity, eclipsing the highest activity of our best Pt-Mn/C prepared in the absence of SC. XRD studies verified the formation of the Pt-Mn intermetallic phase upon heat treatment. Furthermore, transmission electron microscopy studies revealed that catalysts prepared using the SC additive were more resistant to particle size growth during heat treatment.

Thermally induced changes in the structure and ethanol oxidation activity of Pt0.25Mn0.75/C

Decreasing the cost associated with platinum based catalysts along with improving catalytic properties is a major challenge for commercial direct alcohol fuel cells (DAFC). In this work, Pt/C and Pt–Mn/C alloys have been synthesized and the impact of heat treatment on the structure and electrochemical properties of these catalysts was investigated. The structure, composition and thermal properties of the samples were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). TGA and XRD data showed the Pt–Mn deposits did not have a uniform structure. Several phase transitions occurred upon heat treatment of the catalysts at temperatures between 500 and 950°C. Cyclic and linear sweep voltammetry illustrated that the ethanol oxidation reaction (EOR) activity of pure Pt and Pt–Mn alloy catalysts was altered significantly by heat treatment. The highest EOR activity was achieved with a Pt–Mn alloy that was annealed at 700°C for 4h, exceeding the EOR activity of the pure Pt and untreated Pt–Mn alloy catalysts. XRD analysis indicated that at 700°C an ordered PtMn intermetallic phase was formed and that these highly alloyed particles were the reasons for the enhanced EOR activity.

Effect of acid functionalised carbon supports for Pd–Ni–Sn catalyst on ethanol oxidation reaction

The reduction method was used to prepare catalysts on carbon black (CB), functionalised carbon black (CBsn), multi-walled carbon nanotubes (MWCNTs) and functionalised MWCNTs (MWCNTsn) to improve the catalytic activity for ethanol oxidation reaction.

Pd nanoparticles anchored on carbon-doped TiO2 nanocoating support for ethanol electrooxidation in alkaline media

Carbon-doped TiO2 nanocoating (TiO2-C) on carbon black (CB) was prepared and employed as the support of Pd catalyst for ethanol oxidation reaction (EOR) in alkaline media. The obtained catalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. TEM characterization shows that TiO2 nanocoating is formed uniformly on CB and still preserves its structure with no apparent sintering after carbon doping, and Pd particles are well dispersed on the conductive TiO2-C support. XRD characterization shows that TiO2-C presents an anatase structure. XPS characterization shows that oxygen vacancy defects resulting from carbon doping present in TiO2-C. Cyclic voltammetry (CV) and chronoamperometry (CA) results demonstrate that the as-prepared Pd/TiO2-C catalyst exhibits much enhanced catalytic activity and stability for EOR in alkaline media than Pd/C catalyst. The enhanced activity presented by the Pd/TiO2-C catalyst may result from the strong interactions between TiO2 and Pd, the facilitated oxidation removal of CH3COads intermediate, and the facilitated transportation of ethanol to Pd active sites.

Palladium and palladium–tin supported on multi wall carbon nanotubes or carbon for alkaline direct ethanol fuel cell

Pd and PdSn (Pd:Sn atomic ratios of 90:10), supported on Multi Wall Carbon Nanotubes (MWCNT) or Carbon (C), are prepared by an electron beam irradiation reduction method. The obtained materials are characterized by X-Ray diffraction (XRD), Energy dispersive X-ray analysis (EDX), Transmission electron Microscopy (TEM) and Cyclic Voltammetry (CV). The activity for ethanol electro-oxidation is tested in alkaline medium, at room temperature, using Cyclic Voltammetry and Chronoamperometry (CA) and in a single alkaline direct ethanol fuel cell (ADEFC), in the temperature range of 60–90 °C. CV analysis finds that Pd/MWCNT and PdSn/MWCNT presents onset potentials changing to negative values and high current values, compared to Pd/C and PdSn/C electrocatalysts. ATR-FTIR analysis, performed during the CV, identifies acetate and acetaldehyde as principal products formed during the ethanol electro-oxidation, with low conversion to CO2. In single fuel cell tests, at 85 °C, using 2.0 mol L−1 ethanol in 2.0 mol L−1 KOH solutions, the electrocatalysts supported on MWCNT, also, show higher power densities, compared to the materials supported on carbon: PdSn/MWCNT, presents the best result (36 mW cm−2). The results show that the use of MWCNT, instead of carbon, as support, plus the addition of small amounts of Sn to Pd, improves the electrocatalytic activity for Ethanol Oxidation Reaction (EOR).

Facile preparation of rutile Ti0.7W0.3O2 with high conductivity and its effect on enhanced electrocatalytic activity of Pt as catalyst support

Rutile Ti0.7W0.3O2 with high conductivity is prepared in a mild conditon and characterized by X-ray diffraction (XRD), scanning electron mocroscopy (SEM) and electrochemical impedance spectroscopy (EIS). Pt nanoparticles are loaded on the non-carbon catalyst support Ti0.7W0.3O2 and the electrocatalytic activity of Pt/Ti0.7W0.3O2 is evaluated by cyclic voltammetry (CV), chronoampermetry (CA) and rotating disk electrode (RDE) experiments. The Pt/Ti0.7W0.3O2 exhibits higher electrocatalytic activity of ethanol oxidation reaction (EOR) than commercial Pt/C (E-TEK) and its durability is also enhanced. The oxygen reduction reaction (ORR) activity of Pt/Ti0.7W0.3O2 is increased compared with that of Pt/C. The activation energy studies show that the dissociation adsorption of ethanol on Pt/Ti0.7W0.3O2 is as easy as that on Pt/C in kinetic-controlled process of ethanol. X-ray photoelectron spectroscopy (XPS) analysis shows that electrocatalytic activity enhancement of Pt/Ti0.7W0.3O2 is attributed to the charge transfer from Ti0.7W0.3O2 to Pt.

Dry-grinding Synthesized Multi-walled Carbon Nanotubes Supported PdO Catalyst for Ethanol Oxidation Reaction

For the first time, it was found that dry-grinding the mixture containing technical grade PdO and multi-walled carbon nanotubes (MWCNTs) can generate a catalyst with ultrahigh electrocatalytic activity for ethanol oxidation reaction (EOR). The as-prepared catalysts were denoted as PdO/MWCNTs. For a comparison, the graphene and graphite supported PdO samples were also prepared using the same process, leading to the formation of PdO/graphene and PdO/graphite catalysts respectively. The structural details, the morphologies as well as the particle sizes of the prepared catalysts are mainly characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Although no novel diffraction peaks were observed in the XRD patterns of the resulting samples, the morphologies of the samples after the dry-grinding process have changed greatly as compared to the starting materials of PdO. The results also indicate that the PdO/MWCNTs catalysts show the smallest particle sizes among all the prepared catalysts. The catalytic activities of the prepared PdO/MWCNTs catalysts towards EOR are examined by electrochemical measurements, and the results obtained from cyclic voltammery (CV) test demonstrated that the PdO/MWCNTs catalyst delivers a forward peak current density for EOR of 5029mAmg−1 at a scan rate of 50mVs−1, which is about 2.1 times higher than the reported value (2361mAmg−1) obtained on the (Pd/C) catalyst. After detailed analysis, it is thought that the easier hydrogen evolution process on the PdO/MWCNTs catalyst is regarded as the main reason for its excellent electrochemical performance as compared to other catalysts, i.e., PdO/graphene and PdO/graphite. Most interestingly, the as-prepared catalyst has electrocatalytic activity for both methanol oxidation reaction and formic acid oxidation, which were also explored approximately in this preliminary work.

Electro-oxidation of ethanol on ternary Pt–Sn–Ce/C catalysts

Ternary Pt–Sn–Ce/C catalysts were prepared by a modified formic acid method, and their activity for the ethanol oxidation reaction (EOR) was compared to that of Pt–Sn/C, Pt–Ce/C and Pt/C catalysts. No bulk alloy formation was detected by XRD analysis. XPS measurements indicated no segregation on the catalyst surface and the presence of Sn(0) and SnOx, Ce2O3 and CeO2 oxides. The onset potential for CH3CH2OH oxidation on Pt–Sn/C and Pt–Sn–Ce/C (60:20:20) catalysts, which have the highest Sn content on the surface, was lower than that of Pt–Sn–Ce/C (70:20:10) and (50:20:30), Pt–Ce/C and Pt/C catalysts. This work highlights the dependence on the potential of the effect of cerium in Pt–Sn–Ce/C catalysts on the EOR activity and on the reaction mechanism. By derivative voltammograms, different reaction pathways at different potentials, involving Sn (at ca. 0.44V vs. RHE), Sn+Ce (at ca. 0.55V vs. RHE) and Ce (at ca. 0.67V vs. RHE) were inferred. The Pt–Sn–Ce/C catalysts were less tolerant to poisoning by ethanol oxidation intermediate species than Pt/C and Pt–Sn/C, but more stable than Pt–Ce/C catalysts. DEFC tests at 90°C indicated that a higher Sn surface content is more effective for ethanol oxidation than the addition of Ce to Pt–Sn/C.

Reduced graphene oxide supported palladium nanoparticles via photoassisted citrate reduction for enhanced electrocatalytic activities.

Reduced graphene oxide (rGO) supported palladium nanoparticles (Pd NPs) with a size of ∼3 nm were synthesized using one-pot photoassisted citrate reduction. This synthetic approach allows for the formation and assembly of Pd NPs onto the rGO surface with a desired size and can be readily used for other metal NP preparation. The prepared rGO-Pd exhibited 5.2 times higher mass activity for ethanol oxidation reaction than the commercial platinum/carbon (Pt/C). In the oxygen reduction reaction tests, rGO-Pd exhibited comparable activity compared with Pt/C and maintained its high performance after 4000 cycles of potential sweep. These results demonstrate that our synthetic approach is effective for preparing graphene-supported metal NPs with excellent activity and stability in ethanol oxidation and oxygen reduction reactions.

Pd-Au/C catalysts with different alloying degrees for ethanol oxidation in alkaline media

High alloyed Pd-Au/C catalyst is prepared through a rate-limiting strategy in water/ethylene glycol solution. Pd/C and low alloyed Pd-Au/C catalysts are prepared with trisodium citrate and sodium borohydride as stabilizing and reducing agents, respectively. Transmission electron microscopy (TEM) shows that the synthesized Pd(Au) particles are well dispersed on the catalysts. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) show that the high alloyed Pd-Au/C catalyst presents a relatively homogenous structure while the low alloyed Pd-Au/C catalyst presents a Pd-rich shell/Au-rich core structure. Electrochemical characterization shows that the low alloyed Pd-Au/C catalyst exhibits the best catalytic activity for ethanol oxidation reaction (EOR) in alkaline media, which could be attributed to its relatively large exposed Pd surface area as compared with the high alloyed Pd-Au/C catalyst due to its Pd-rich shell structure and its enhanced adsorption of OHads as compared with Pd/C catalyst due to its core-shell structure.

Efficient C-C bond splitting on Pt monolayer and sub-monolayer catalysts during ethanol electro-oxidation: Pt layer strain and morphology effects.

Efficient catalytic C-C bond splitting coupled with complete 12-electron oxidation of the ethanol molecule to CO2 is reported on nanoscale electrocatalysts comprised of a Pt monolayer (ML) and sub-monolayer (sML) deposited on Au nanoparticles (Au@Pt ML/sML). The Au@Pt electrocatalysts were synthesized using surface limited redox replacement (SLRR) of an underpotentially deposited (UPD) Cu monolayer in an electrochemical cell reactor. Au@Pt ML showed improved catalytic activity for ethanol oxidation reaction (EOR) and, unlike their Pt bulk and Pt sML counterparts, was able to generate CO2 at very low electrode potentials owing to efficient C-C bond splitting. To explain this, we explore the hypothesis that competing strain effects due to the Pt layer coverage/morphology (compressive) and the Pt-Au lattice mismatch (tensile) control surface chemisorption and overall activity. Control experiments on well-defined model Pt monolayer systems are carried out involving a wide array of methods such as high-energy X-ray diffraction, pair-distribution function (PDF) analysis, in situ electrochemical FTIR spectroscopy, and in situ scanning tunneling microscopy. The vibrational fingerprints of adsorbed CO provide compelling evidence on the relation between surface bond strength, layer strain and morphology, and catalytic activity.

Highly Active Graphene-Supported NixPd100–xBinary Alloyed Catalysts for Electro-Oxidation of Ethanol in an Alkaline Media

A series of graphene (G)-supported NixPd100–x binary alloyed catalysts (BACs) were prepared with variation of Ni and Pd metal loading through a facile chemical reduction method and were used as an anode catalyst for ethanol oxidation reaction (EOR), which is superior fuels for direct ethanol fuel cells (DEFCs). The X-ray diffraction (XRD) data reveals that the NixPd100–x/G catalysts were homogeneously alloyed, and Ni was present with the oxidized form. The transmission electron microscopy (TEM) images also suggest the alloyed formation with different shapes of metal nanoparticles (NPs). The electrochemical properties of the catalysts were evaluated using cyclic voltammetry (CV) and chronoamperometry (CA) in 1 M KOH electrolyte. The higher catalytic activity for EOR was increased in the order Ni75Pd25/G > Ni0Pd100/G > Ni25Pd75/G > Ni50Pd50/G. Among NixPd100–x/G BACs, the Ni50Pd50/G catalyst showed the highest onset potential (−0.8 V) on CV and long-term stability on amperometric measurements. The overall p...