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An electrocatalyst decorated with nickel oxide nanoflower and borophene (PdNiONF/B) has been presented as a possible catalyst for the ethanol oxidation reaction (EOR) in alkaline media. The crystal microstructure, composition, and morphology of the product were analyzed by using X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Energy‐dispersive X‐ray spectroscopy (EDS). The catalytic activity of the PdNiONF/B for ethanol electrooxidation was assessed by using electrochemical impedance spectroscopy, cyclic voltammetry, and chronoamperometry. PdNiONF/B shows a high current at 0.12 mA as compared to palladium on carbon (Pd/C) and palladium on borophene (Pd/B) in 2 M of NaOH+ 2 M of EtOH. In addition, PdNiONF/B is stable and more tolerant of impurities. This observation suggests that PdNiONF/B possesses a better catalytic behavior. The ratio of the backward peak current (Ibwd) to the forward peak current (Ifwd) (Ibwd/Ifwd) in a 2 M of NaOH+2 M of EtOH is equal to (Ibwd/Ifwd) 1.0 V vs. Ag|AgCl for PdNiONF/B catalyst. This ratio indicates that PdNiONF/B has an excellent tolerance to ethanol intermediate species poisoning. [ABSTRACT FROM AUTHOR]

The ethanol oxidation reaction (EOR) is crucial in direct alcohol fuel cells and chemical production. However, the electro-oxidation of ethanol molecules to produce acetaldehyde and carbon monoxide can poison the active sites of nanocatalysts, resulting in reduced performance and posing challenges in achieving high activity and selectivity for ethanol oxidation. In this study, we employed a dynamic seed-mediated method to precisely modify highly dispersed Ru sites onto well-defined Pd nanocrystals. The oxyphilic Ru sites serve as "OH valves", regulating water dissociation, while the surrounding Pd atomic arrangements control electronic states for the oxidation dehydrogenation of carbonaceous intermediates. Specifically, Ru0.040@Pd nanocubes (Ru:Pd = 0.04 at.%), featuring (100) facets in Ru-Pd4 configurations, demonstrate an outstanding mass activity of 6.53 A ⋅ mg Pd − 1 in EOR under alkaline conditions, which is 6.05 times higher than that of the commercial Pd/C catalyst (1.08 A ⋅ mg Pd − 1 ). Through in-situ experiments and theoretical investigations, we elucidate that the hydrophilic Ru atoms significantly promote the dynamic evolution of H2O dissociation into OHads species, while the electron redistribution from Ru to adjacent Pd concurrently adjusts the selective oxidation of C2 intermediates. This host–guest interaction accelerates the subsequent oxidation of carbonaceous intermediates (CH3COads) to acetate, while preventing the formation of toxic ⋆CHx and ⋆CO species, which constitutes the rate-determining step. [ABSTRACT FROM AUTHOR]

The progress in making macro- and mesoporous layers of porous silicon formed through Pd-assisted etching is analyzed. Different formation times and etching solution temperatures (varying from 25 to 75°C) are taken as the parameters. The layers of porous silicon obtained exhibit ethanol electro-oxidation properties. High values of the dissolution rate of the porous silicon are confirmed at a temperature of 75°C resulting in dramatic thinning and decreasing the specific surface area of the macro- and mesoporous layers, respectively. The resulting porous layers have different surface energies and surface areas. The samples exhibit different rates of ethanol dehydrogenation and differ in the number of dehydrogenated ethanol molecules. This is promising to control the activity of the electrode material in ethanol fuel cells. [ABSTRACT FROM AUTHOR]

Abstract An electrocatalyst decorated with nickel oxide nanoflower and borophene (PdNiONF/B) has been presented as a possible catalyst for the ethanol oxidation reaction (EOR) in alkaline media. The crystal microstructure, composition, and morphology of the product were analyzed by using X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Energy‐dispersive X‐ray spectroscopy (EDS). The catalytic activity of the PdNiONF/B for ethanol electrooxidation was assessed by using electrochemical impedance spectroscopy, cyclic voltammetry, and chronoamperometry. PdNiONF/B shows a high current at 0.12 mA as compared to palladium on carbon (Pd/C) and palladium on borophene (Pd/B) in 2 M of NaOH+ 2 M of EtOH. In addition, PdNiONF/B is stable and more tolerant of impurities. This observation suggests that PdNiONF/B possesses a better catalytic behavior. The ratio of the backward peak current (Ibwd) to the forward peak current (Ifwd) (Ibwd/Ifwd) in a 2 M of NaOH+2 M of EtOH is equal to (Ibwd/Ifwd) 1.0 V vs. Ag|AgCl for PdNiONF/B catalyst. This ratio indicates that PdNiONF/B has an excellent tolerance to ethanol intermediate species poisoning.

Spinel-based materials are promising candidates as electro-catalysts for the oxidation of alcohol fuels. In the present study, electrospun CoFe 2 O 4 spinel nanostructures were prepared by electrospinning technique and the subsequent thermal treatment processes. Then, the bimetallic Au–Pd–CoFe 2 O 4 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–CoFe 2 O 4 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–CoFe 2 O 4 with a scan rate of 50 mVs−1, which is due to the synergistic effect of Au and Pd on CoFe 2 O 4. 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. • Au–Pd–CoFe 2 O 4 are synthesized by electrospinning and chemical reduction technique as an anode catalyst. • The ratio of Au to Pd was investigated in the electro-catalytic performance of Au–Pd–CoFe 2 O 4 spinel for ethanol oxidation. • The Au–Pd–CoFe 2 O 4 catalyst illustrated high current density and suitable potentials. • Au–Pd–CoFe 2 O 4 catalyst was progressed of C–H breaking and CO ad endurance. [ABSTRACT FROM AUTHOR]

The composition and atomic structure of nanoalloy electrocatalysts play an important role in the ethanol oxidation reaction (EOR). To study this and develop an electrochemically active electrocatalyst towards ethanol electro-oxidation, a second oxophilic metal has generally been initiated as an alloy, capable of enhancing the electrocatalytic activity of platinum. Given the above, the present investigation deals with nanoparticles of PtRu with different bimetallic compositions supported on multi-walled carbon nanotube (MWCNT) (C) for their activity on the ethanol electro-oxidation. The structure, morphology, and bonding of the electrocatalysts were studied by XRD, SEM, TEM, EDXRF, and FTIR. Electrochemical methods like cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) were used to explore the catalytic activity towards ethanol electro-oxidation. This study focused on establishing the relationship between the electrocatalysts' composition, atomic structure, and catalytic activity for the EOR. All the results of physical and electrochemical studies revealed an intriguing composition–structure–activity relationship for the PtRu electrocatalysts under EOR experimental conditions. In particular, the alloy with a Pt/Ru ratio of ∼ 84 : 16 was found to exhibit a maximum EOR activity as a function of the bimetallic composition. Notably, the catalytic activities of the C/PtRu electrocatalysts showed a significant improvement during the EOR. The results show a new perspective in the development of C/PtRu electrocatalysts regarding ethanol oxidation reaction which is important for the rational design and synthesis of active nanoalloy electrocatalysts for direct ethanol fuel cell (DEFC). [ABSTRACT FROM AUTHOR]

An easy and efficient method was considered to enhance the activity of Pt/C catalyst for ethanol oxidation by formation of a platinum-cobalt alloy via electrodeposition technique. The morphology and structural properties of the prepared Pt-Co/C alloy catalyst were determined by SEM, EDX and XRD. The XRD curves confirmed Pt characteristic peaks at around 2θ = 39.76° (111) and 46.23° (200) while the existence of Co was not clear at 2θ = 44.5° and 51.85° owing to its alloying with Pt. CV, CA, EIS techniques were employed to examine the electrochemical behavior of the Pt-Co/C catalyst. The impedance data were fitted to the Randles circuit to obtain the parameters for a single faradic reaction coupled with mass transfer. The Pt-Co/C catalyst showed better performance in terms of the onset potential and current density. The sample containing Pt-Co/C catalyst exhibited about 2 times more current density than the commercial Pt/C catalyst. [ABSTRACT FROM AUTHOR]

Due to their environmentally friendly nature and high energy density, direct ethanol fuel cells have attracted extensive research attention in recent decades. However, the actual Faraday efficiency of the ethanol oxidation reaction (EOR) is much lower than its theoretical value and the reaction kinetics of the EOR is sluggish due to insufficient active sites on the electrocatalyst surface. Pt/C is recognized as one of the most promising electrocatalysts for the EOR. Thus, the microscopic interfacial reaction mechanisms of the EOR on Pt/C were systematically studied in this work. In metal hydroxide solutions, hydrated alkali cations were found to bind with OHad through noncovalent interactions to form clusters and occupy the active sites on the Pt/C electrocatalyst surface, thus resulting in low Faraday efficiency and sluggish kinetics of the EOR. To reduce the negative effect of the noncovalent interactions on the EOR, a shield was made on the electrocatalyst surface using 4‐trifluoromethylphenyl, resulting in twice the EOR catalytic reactivity of Pt/C. [ABSTRACT FROM AUTHOR]

Abstract Due to their environmentally friendly nature and high energy density, direct ethanol fuel cells have attracted extensive research attention in recent decades. However, the actual Faraday efficiency of the ethanol oxidation reaction (EOR) is much lower than its theoretical value and the reaction kinetics of the EOR is sluggish due to insufficient active sites on the electrocatalyst surface. Pt/C is recognized as one of the most promising electrocatalysts for the EOR. Thus, the microscopic interfacial reaction mechanisms of the EOR on Pt/C were systematically studied in this work. In metal hydroxide solutions, hydrated alkali cations were found to bind with OHad through noncovalent interactions to form clusters and occupy the active sites on the Pt/C electrocatalyst surface, thus resulting in low Faraday efficiency and sluggish kinetics of the EOR. To reduce the negative effect of the noncovalent interactions on the EOR, a shield was made on the electrocatalyst surface using 4‐trifluoromethylphenyl, resulting in twice the EOR catalytic reactivity of Pt/C.

The objective of this work is to employ chemometric tools to investigate the influence of the synthesis parameters in platinum electrodeposition on a titanium substrate using cyclic voltammetry. Through a 22 factorial design, using as response the maximum peak current density during the ethanol electro-oxidation, one can observe that the number of cycles and the scan rate are both significant, but the interaction between them is not. The maximum peak current density is observed for the electrode obtained with NC = 20 cycles and SR = 200 mV s−1. The structural characterization indicates that the surface irregularity of the substrate causes an uneven growth of the (200) and (220) crystallographic planes, which present different performances in the electro-oxidation of ethanol. The response surface methodology indicates that the best experimental condition is that obtained with 10 cycles and 218 mV s−1. The Pt/Ti electrodes prepared with the optimized parameters are promising. A 22 factorial design was applied to prepare Pt/Ti for ethanol eletro-oxidation. Pt electrodeposits have shown an atypical "house of cards" morphology. Preferential orientation of Pt on Ti surface are related to better activity. Response surface methodology points 10 cycles at 218 mV s−1 as the best condition. [ABSTRACT FROM AUTHOR]

Bimetallic Pt3Eu/C, Pt3La/C, and Pt3Ce/C electrocatalysts have been prepared, characterized, and tested for ethanol electro-oxidation (EEO). The materials were synthesized by chemical reduction with NaBH4, rendering nanosized particles with actual compositions close to the nominals and no alloy formation. X-ray photoelectron spectroscopy (XPS) confirmed that the auxiliary rare-earth metals were present on the surface in oxide form. The electrochemical analyses in acid and alkaline EEO evidenced that, compared to Pt/C, the addition of rare earth metals in the form of oxides reduced the onset potential, increased the current density, and enhanced the stability. The results were fully confirmed in the DEFC single-cell measurements. Finally, the presence of rare earth metals in the oxidized form increased the percentage of acetic acid as the final product, making the electrocatalysts more selective and efficient than Pt/C, where acetaldehyde was the main product. [ABSTRACT FROM AUTHOR]

In-situ chemical reduction technique was exploited to fabricate free-standing and binder-free active nanocatalyst materials for direct ethanol fuel cells using nickel nanoparticles onto polyvinylidenefluoride-co-hexafluoropropylene membrane [Ni/PVdF-HFP]. Homogeneously distributed nickel nanoparticles with face-centered cubic structure were observed onto smooth membrane surfaces. Cyclic voltammetric measurements indicated the enhanced activity of Ni/PVdF-HFP membrane for oxidizing the alcohol molecules in NaOH solution. The measured oxidation current density increased with increasing the added ethanol concentration into the supporting electrolyte up to 0.64 M. Some kinetic parameters were calculated such as the charge transfer coefficient (α), Tafel slope and exchange current density values to record 0.468, 369 mV dec−1 and 1.28 μA cm−2, respectively. The three dimensional nanostructure of these fabricated metallic membranes and the increased number of their active voids could provide largely exposed surface areas for adsorbed alcohol molecules. The good stability of nickel nanoparticles onto PVdF-HFP membrane surface with minimum leaching level during prolonged ethanol oxidation in alkaline solution can offer unique possibilities for utilizing these polymeric electrocatalyst structures for energy production applications.

Among direct alcohol fuel cells, the ethanol fuel cell is considered the most acceptable in terms of safety and power density. In this research, a Pt/CNFs-GNPs /GDL electrode was developed using GNPs and CNFs as a supporting medium on carbon paper and the electrodeposition method to deposit Pt catalyst. The morphology and structure features of the prepared film samples were characterized by FESEM and XRD. Pt particles of about 6.53 nm were uniformly deposited on the porous support. Catalytic activities of the prepared electrode for the ethanol oxidation reaction were evaluated through cyclic voltammetry measurements. Based on the electrochemical properties, the as-prepared Pt/CNFs-GNPs/GDL electrocatalyst exhibited a comparable activity for ethanol oxidation reaction for the Pt/C, which may be attributed to the high specific surface area of the CNFs support as well as high conductivity of graphene nanoplates. A notable reduction in the onset and peak potential of ethanol electro-oxidation from 0.55 and 0.81V for Pt/C/GDL to 0.50 and 0.79V for Pt/CNFs-GNPs/GDL electrodes, as well as a substantial increment in anodic Tafel slope values from 376 mV to 521 mV, indicates that an increase in the activity for EOR is achieved by replacing C with CNFs-GNPs.

Ethanol is considered an alternative fuel to power fuel cells, especially due to its ease of transport and storage and renewable production on a large scale. However, its use in direct ethanol fuel cells (DEFC) is still limited by incomplete electro-oxidation and slow reaction kinetics. Modeling approaches have focused on investigating different reaction mechanisms, but so far, no formal analysis of model parameter sensitivity has been conducted. This work modeled and identified sensitive parameters for different types of Pt–Sn catalysts previously prepared by our research group that displayed good performance in the 5–15 mW/cm2 range (relative to a performance of 12 mW/cm2 achieved by a commercial ETEK catalyst). Analyses to study the effect of these parameters on coverage fraction distribution, reaction rates and possible correlations were also performed. The model was developed based on Butler–Volmer kinetics and on a reaction mechanism previously reported in the literature. Statistical developments were considered to compute parameter uncertainties for a non-linear system with non-linear restrictions. The model achieved very good fits to experimental data, with low RMSE values between 0.22 × 10−4 and 4.2 × 10−4 A/cm2, while also showing surface coverage fraction distributions in agreement with other experiment-based works from the literature. All catalysts taken into account, the most sensitive parameters were the reaction rate constants associated with the formation of adsorbed CH3CO, and the direct and reverse water dissociative adsorption reactions, respectively. Additional analyses suggested that there is not much correlation between the parameters. The results from this work could contribute to the state-of-the-art DEFC models by providing insights into which variables may be assumed constant or which ones have the greatest impact on the model output, thus helping to reduce the model size and computational time for future broader DEFC models. [ABSTRACT FROM AUTHOR]

Direct ethanol fuel cells (DEFCs) are considered the most suitable direct alcohol fuel cell (DAFC) in terms of safety and current density. The obstacle to DEFC commercialization is the low reaction kinetics of ethanol (C2H5OH) oxidation because of the poor performance of the electrocatalyst. In this study, for the first time, graphene nanoplates (GNPs) were coated with sulfated zirconium dioxide (ZrO2) as adequate support for platinum (Pt) catalysts in DEFCs. A Pt/S-ZrO2-GNP electrocatalyst was prepared by a new process, polyol synthesis, using microwave heating. Field emission scanning electron microscope (FESEM) imaging revealed well-dispersed platinum nanoparticles supported on the S-ZrO2-GNP powder. Analysis of the Fourier transform infrared (FTIR) spectrometry confirmed that sulfate modified the surfaces of the sample. In X-ray diffraction (XRD), no effect of S-ZrO2 on the crystallinity net in Pt was found. Pt/S-ZrO2-GNP electrode outperformed those with unsulfated counterparts, primarily for the higher access with electron and proton, confirming sulfonating as a practical approach for increasing the performance, electrocatalytic activity, and carbon monoxide (CO) tolerance in an electrocatalyst. A considerable decrease in the voltage of the CO electrooxidation peak from 0.93 V for Pt/C to 0.76 V for the Pt/S-ZrO2-GNP electrode demonstrates that the new material increases activity for CO electrooxidation. Moreover, the as-prepared Pt/S-ZrO2-GNPs electrocatalyst exhibits high catalytic activity for the EOR in terms of electrochemical surface area with respect to Pt/ZrO2-GNPs and Pt/C (199.1 vs. 95 and 67.2 cm2.mg−1 Pt), which may be attributed to structural changes caused by the high specific surface area of graphene nanoplates catalyst support and sulfonating effect as mentioned above. Moreover, EIS results showed that the Pt/S-ZrO2-GNPs electrocatalyst has a lower charge transfer resistance than Pt/ ZrO2-GNPs and Pt/C in the presence of ethanol demonstrating an increased ethanol oxidation activity and reaction kinetics by Pt/S-ZrO2-GNPs. [ABSTRACT FROM AUTHOR]

Bimetallic Pt3Eu/C, Pt3La/C, and Pt3Ce/C electrocatalysts have been prepared, characterized, and tested for ethanol electro-oxidation (EEO). The materials were synthesized by chemical reduction with NaBH4, rendering nanosized particles with actual compositions close to the nominals and no alloy formation. X-ray photoelectron spectroscopy (XPS) confirmed that the auxiliary rare-earth metals were present on the surface in oxide form. The electrochemical analyses in acid and alkaline EEO evidenced that, compared to Pt/C, the addition of rare earth metals in the form of oxides reduced the onset potential, increased the current density, and enhanced the stability. The results were fully confirmed in the DEFC single-cell measurements. Finally, the presence of rare earth metals in the oxidized form increased the percentage of acetic acid as the final product, making the electrocatalysts more selective and efficient than Pt/C, where acetaldehyde was the main product.

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

In this study, we report nanoporous gold (NPG) as an economic, efficient, and stable alternative electrocatalyst for methanol electro-oxidation. The said sample was successfully prepared from an Fe-rich metastable Au33Fe67 supersaturated solid solution acting as the precursor, which was formed into ribbons by the phenomenon of rapid solidification using melt-spinning technique. The as-quenched ribbon was then chemically dealloyed in 1 M HCl at 70 °C for different durations of time. A homogeneous, free-standing, and mechanically stable NPG sample was obtained with tunable ligament shape and size. The morphology and composition were characterized by using SEM with EDS, while the structure by XRD. The sample was examined as an electrocatalyst for methanol electro-oxidation profiting off its large surface area; cyclic voltammetry (CV) was the technique employed for electrochemical studies. In a basic solution of methanol and KOH, the sample displays a low peak potential of 0.47 V vs. Ag/AgCl for methanol electro-oxidation with a high peak current density of 0.43 mA/cm2. In addition, it demonstrates outstanding stability and high poisoning tolerance. It is noteworthy that the fabrication process of the NPG sample from start to end was intentionally opted to be sustainable, cost-effective, rapid, and feasible. The usage of critical raw materials was avoided. As a whole, the properties and results put forth by the NPG sample make it an inexpensive, sustainable, and excellent alternative as an electrocatalyst for methanol electro-oxidation. [ABSTRACT FROM AUTHOR]

Ethanol is considered an alternative fuel to power fuel cells, especially due to its ease of transport and storage and renewable production on a large scale. However, its use in direct ethanol fuel cells (DEFC) is still limited by incomplete electro-oxidation and slow reaction kinetics. Modeling approaches have focused on investigating different reaction mechanisms, but so far, no formal analysis of model parameter sensitivity has been conducted. This work modeled and identified sensitive parameters for different types of Pt–Sn catalysts previously prepared by our research group that displayed good performance in the 5–15 mW/cm2 range (relative to a performance of 12 mW/cm2 achieved by a commercial ETEK catalyst). Analyses to study the effect of these parameters on coverage fraction distribution, reaction rates and possible correlations were also performed. The model was developed based on Butler–Volmer kinetics and on a reaction mechanism previously reported in the literature. Statistical developments were considered to compute parameter uncertainties for a non-linear system with non-linear restrictions. The model achieved very good fits to experimental data, with low RMSE values between 0.22 × 10−4 and 4.2 × 10−4 A/cm2, while also showing surface coverage fraction distributions in agreement with other experiment-based works from the literature. All catalysts taken into account, the most sensitive parameters were the reaction rate constants associated with the formation of adsorbed CH3CO, and the direct and reverse water dissociative adsorption reactions, respectively. Additional analyses suggested that there is not much correlation between the parameters. The results from this work could contribute to the state-of-the-art DEFC models by providing insights into which variables may be assumed constant or which ones have the greatest impact on the model output, thus helping to reduce the model size and computational time for future broader DEFC models.

Direct ethanol fuel cells (DEFCs) are considered the most suitable direct alcohol fuel cell (DAFC) in terms of safety and current density. The obstacle to DEFC commercialization is the low reaction kinetics of ethanol (C2H5OH) oxidation because of the poor performance of the electrocatalyst. In this study, for the first time, graphene nanoplates (GNPs) were coated with sulfated zirconium dioxide (ZrO2) as adequate support for platinum (Pt) catalysts in DEFCs. A Pt/S-ZrO2-GNP electrocatalyst was prepared by a new process, polyol synthesis, using microwave heating. Field emission scanning electron microscope (FESEM) imaging revealed well-dispersed platinum nanoparticles supported on the S-ZrO2-GNP powder. Analysis of the Fourier transform infrared (FTIR) spectrometry confirmed that sulfate modified the surfaces of the sample. In X-ray diffraction (XRD), no effect of S-ZrO2 on the crystallinity net in Pt was found. Pt/S-ZrO2-GNP electrode outperformed those with unsulfated counterparts, primarily for the higher access with electron and proton, confirming sulfonating as a practical approach for increasing the performance, electrocatalytic activity, and carbon monoxide (CO) tolerance in an electrocatalyst. A considerable decrease in the voltage of the CO electrooxidation peak from 0.93 V for Pt/C to 0.76 V for the Pt/S-ZrO2-GNP electrode demonstrates that the new material increases activity for CO electrooxidation. Moreover, the as-prepared Pt/S-ZrO2-GNPs electrocatalyst exhibits high catalytic activity for the EOR in terms of electrochemical surface area with respect to Pt/ZrO2-GNPs and Pt/C (199.1 vs. 95 and 67.2 cm2.mg−1 Pt), which may be attributed to structural changes caused by the high specific surface area of graphene nanoplates catalyst support and sulfonating effect as mentioned above. Moreover, EIS results showed that the Pt/S-ZrO2-GNPs electrocatalyst has a lower charge transfer resistance than Pt/ ZrO2-GNPs and Pt/C in the presence of ethanol demonstrating an increased ethanol oxidation activity and reaction kinetics by Pt/S-ZrO2-GNPs.

The present work deals with a new methodology to produce a sustainable carbon material through a simple synthetic route, and its performance as Ni-based electrocatalyst support. Such porous carbon was easily synthesized from the raw Kraft black liquor, a by-product rich in lignin, by chemical polymerization in alkaline medium with a nickel source and subsequent activation by CO2. Nickel nanoparticles were homogeneously distributed in the samples, as revealed by STEM images. XPS analyses and BET method indicated the presence of Ni species in the synthesized material and a micro-mesoporous structure, respectively. The electrochemical characterization in NaOH and NaOH+ ethanol solutions showed that the as-prepared material has the relevant potential to be applied as electrocatalyst for Ethanol Oxidation Reaction (EOR) in alkaline medium. [ABSTRACT FROM AUTHOR]

Abstract By combining the hydrothermal and pulsed laser deposition methods, several three‐dimensional Pt catalysts on TiO2 structures are prepared and used for the electro‐oxidation of ethanol in acidic medium. SEM reveals that TiO2 prepared with 0.6 M of HCl consist of a mixture of nanowires and nanorods. For higher HCl concentrations, the TiO2 are either in the form of vertically aligned bars or large branched crystals in the form of flowers‐like. Despite having the same loading of Pt, among the 3D Pt/TiO2/Ti structures, only those with TiO2 prepared with 0.6 M of HCl shows a higher area specific activity and current mass activities exceptionally superior of about >50 times than those of unsupported Pt/Ti catalyst toward ethanol oxidation reaction, which suggests a promising application in ethanol fuel cells.

The development of highly efficient Pt-based nanocatalysts is important for the commercialization of direct ethanol fuel cells (DEFCs) but remains challenging to achieve. Here in, we developed an ingenious strategy to significantly improve the electrocatalytic property of Pt-based catalyst towards ethanol oxidation reactions (EOR) in acid medium by doping tungsten. In this study carbon (Vulcan XC-72R, Ketjen black, carbon nanotubes) supported Pt-surface-enriched platinum–tungsten bimetallic nanoparticles (W@Pt/C, W@Pt/KJ, W@Pt/CNT) were prepared using the etching effect of galvanic replacement on amorphous tungsten nanoparticles. Additionally, no surfactant is used in the preparation of the catalysts. The catalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical methods. From the results, we can conclude that W@Pt nanoparticles were uniformly loaded on each carbon support. Finally, when compared with JM Pt/C, the catalytic activity of W@Pt/C was increased by 30% and the current density retained by W@Pt/C was 1.6 times that of the commercial catalyst (123 mA mgPt−1). At the end of the 3600 s reaction, W@Pt/C retained a current density of 198 mA mg−1 which is 1.6 times that of commercial catalyst JM Pt/C (123 mA mg−1). Also, W@Pt/KJ retained a current density of 176 mA mg−1 which is 1.4 times that of JM Pt/C. Furthermore, the metal oxides (WOX) in the catalyst can easily adsorb -OH species which can transform COads poisoning species to CO2, thus promoting the catalytic activity and stability toward EORs. [ABSTRACT FROM AUTHOR]

Abstract Palladium nanoparticles supported on carbon Vulcan XC72 (Pd/C) and biocarbon (Pd/BC) synthesized by sodium borohydride process were used as catalysts for ethanol electro-oxidation in alkaline media. The biocarbon (BC) from coconut shell with mesoporous and high surface area (792 m2 g−1) was obtained by carbonization at 900 °C and the hydrothermal treatment in a microwave oven. The D-band and G-band intensity ratio (I D/I G) from Raman analysis showed high disorder of the biocarbon, while X-ray photoelectron spectroscopy (XPS) suggests higher percentage of oxygen groups on the surface of biocarbon than of Vulcan XC72. From X-ray diffraction (XRD), it was observed peaks in 2θ degree related to the face centered cubic (fcc) structure of palladium and the mean crystallite sizes calculated based on the diffraction peak of Pd (220) were 5.6 nm for Pd/C and 5.3 nm for Pd/BC. Using Transmission Electron Microscope (TEM), it was observed particles well dispersed on both carbons support materials. The electrocatalytic activity of the materials was investigated by cyclic voltammetry (CV) and chronoamperometry (CA) experiments. The peak current density (on CV experiments) from ethanol electro-oxidation on Pd/BC was 50% higher than on Pd/C, while the current density measured at 15 min of CA experiments was 80% higher on Pd/BC than on Pd/C. The higher catalytic activity of Pd/BC might be related to the large surface area of the biocarbon (792 m2 g−1) vs (239 m2 g−1) of Vulcan carbon, the defects of the biocarbon structure and higher amount of oxygen on the surface than Carbon Vulcan XC 72.

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Electrocatalyst support materials play significant role in the performance, durability and commercialization of fuel cells. This research work describes the preparation of metal oxide (nickel oxide (NiO), cobalt (Co) and copper (Cu) doped NiO) support materials on meshed titanium (Ti) substrate via a simple electro-deposition method for their application as novel support material for palladium (Pd) catalyst. Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques are employed to study morphology, composition and structure of fabricated electrodes, respectively. The electrocatalytic performance of fabricated electrodes toward ethanol oxidation reaction (EOR) in alkaline solution is examined by the cyclic voltammetry (CV), chronoamperometry (CA) techniques. Low peak potential (−0.2 V), increased peak current density (62.54 mA cm−2) and large electrochemical active surface area (16.02 m2 g−1) were remarkable properties of Pd/Cu–NiO/Ti electrode. The results of other electrochemical measurements, CO-striping voltammetry, long-term stability and electrochemical impedance spectroscopy (EIS) revealed that the Pd/Cu–NiO/Ti electrode has the privileged electrocatalytic performance for EOR relative to other prepared electrodes. Accordingly, the Pd/Cu–NiO/Ti can be considered as a hopeful electrode for ethanol electro-oxidation reaction in DEFCs. Image 1 • The novel electrocatalysts were fabricated via simple electro-deposition technique. • The surface of fabricated catalyst layer was stable and uniform. • The Pd/Cu–NiO/Ti electrode was demonstrated larger EAS than other electrodes. • Doped-NiO supports were promoted catalytic activity of Pd catalyst toward EOR. [ABSTRACT FROM AUTHOR]

To fabricate cost‐effective anode catalysts for direct ethanol fuel cells (DEFC), Pd and a series of bimetallic PdxNi100‐x alloy nano catalyst has been synthesized by adhering toclassical wet chemical synthetic procedure. External capping agents have not been employed for stabilization of the nanoparticles. Several physicochemical characterizations reveal the generation of uniformly dispersed PdxNi100‐x catalysts with average crystallite size 6 nm. The catalytic capability of the PdxNi100‐x/C catalysts for ethanol oxidation reaction (EOR) has been verified by cyclic voltammetry (CV) and chronoamperometry (CA) study. It has been revealed that the peak current density is about 1.2 times higher for ethanol oxidation on Pd80Ni20/C catalyst than similarly synthesized Pd/C catalyst. Moreover, the catalytic proficiency of the bimetallic nano catalysts have been strongly dependent on the Pd : Ni ratio. The poisoning protected ability of the PdxNi100‐x/Ccatalysts leads to show stable performance after several cycles of continuous operation. Cyclic voltammetric and ex‐situ FTIR study of probable intermediates of EOR like acetaldehyde, sodium acetate reveal that Ni facilitate the generation of acetate in comparison to carbonate enlightening the reasonable mechanism of the ethanol oxidation reaction on PdNi surface. [ABSTRACT FROM AUTHOR]

BACKGROUND: In this work, the influence of the anodic catalyst carbonaceous support and the membrane on the electrochemical reforming of ethanol for hydrogen production in alkaline media has been studied. Physicochemical characterization and electrochemical activity measurements were performed for different palladium‐based anodic catalysts. The best anodic catalyst was scaled up to two different membrane electrode assemblies (MEAs) based on anion exchange membranes (AEMs): Tokuyama and KOH‐doped polybenzimidazole (PBI) membranes. In both systems, the influence of the temperature and the stability were evaluated for the electrochemical reforming of ethanol. RESULTS: Among the different investigated catalysts, palladium supported on non‐functionalized low‐surface nanofibers was the best anodic catalyst for the electrochemical reforming of ethanol in alkaline media, which was attributed to the specific physicochemical and textural properties of this material. In addition, the use of a Tokuyama membrane allowed to obtain the highest electrocatalytic activity in hydrogen production together with a suitable stability behavior. Under the optimized conditions, current density values up to 120 mA cm−2 at 1.4 V were obtained, leading to lower energy values for hydrogen production compared with those of water electrolysis in commercial alkaline electrolyzers. CONCLUSION: The choice of palladium supported on non‐functionalized nanofibers as anodic catalyst and a Tokuyama membrane allows to obtain the best MEA configuration for the electrochemical reforming of ethanol for hydrogen production. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In this study, we reported a novel and facile synthesis of self-supported three-dimensional (3D) Ni aerogel using cellulose hydrogel as template followed by removing the template under a moderate condition. The as-prepared Ni aerogel composed of Ni(OH) 2 ultrathin nanofilms and Ni(OH) 2 hybrid nanoparticles had hierarchical porous structure with a considerable specific surface area of 100 m2 g−1, which was beneficial to the enhanced catalytic activity towards ethanol electro-oxidation. Additionally, the self-supported 3D structure of Ni aerogel with free-carbon supports showed a positive effect on the stability of the catalysts. Electrochemical measurements revealed that a high peak current density for Ni aerogel achieved about 27.6 mA cm−2 in an electrolyte of 1.0 M KOH with 0.1 M ethanol, which was 5 times higher than that on alone Ni nanoparticles. Meanwhile, the R ct of Ni aerogel catalyst was only 0.88 Ω cm−2 after the CA measurements for 1800s, which was much smaller than commercial Ni nanoparticles and other similar catalysts reported. The enhanced electrocatalytic performance for ethanol electro-oxidation can be ascribed to the high surface area and predominant properties of above-mentioned special materials structure. This novel Ni aerogel and its excellent properties have great prospects in the application of electro-oxidation catalyst. Unlabelled Image • A novel and facile method to fabricate self-supported three-dimensional Ni aerogel is presented. • The resultant aerogel has hierarchical porous structure and high surface area of 100.1 m2 g−1. • This Ni aerogel has enhanced catalytic activity and stability towards ethanol electrooxidation. [ABSTRACT FROM AUTHOR]

• A facile synthetic route for Au@Pd/C core–shell nanoparticle preparation is proposed. • Core–shell and alloy catalysts were evaluated toward ethanol oxidation. • Catalytic activity toward ethanol oxidation depends on structure and composition. • Au@Pd/C exhibited the highest catalytic activity for ethanol electro-oxidation. • The catalytic activity for Au@Pd/C was two times higher, at 1.1 V, compared to Pd/C. Carbon-supported Pd, Au@Pd core–shell and Au 1– x Pd x -alloyed nanoparticles were prepared by a chemical reduction method and characterized by different experimental techniques, including X-ray powder diffraction, transmission electron microscopy, scanning-transmission electron microscopy using bright-field and high-angle annular dark field detectors and X-ray energy dispersive spectroscopy. The catalytic mass activity toward ethanol oxidation was assessed by cyclic voltammetry and chronoamperometry at room temperature. The measurements showed that the addition of Au enhances remarkably the electrocatalytic activity of the material, due to the bifunctional effect of Au 1– x Pd x /C alloys, and the synergetic effect on Au@Pd/C, resulting in a dissolution resistance of core–shell catalysts at potentials of 1.5 V versus reversible hydrogen electrode. In situ Fourier transform infrared spectroscopy measurements showed that the mechanism for ethanol oxidation depends on the electrocatalyst structure and morphology. Acetate was identified as the main product of ethanol electro-oxidation on the studied electrocatalysts. However, the presence of a core–shell structure on Au@Pd/C resulted in enhanced ethanol oxidation selectivity toward CO 2. The improvement of activity is attributed to the interaction between Pd shell and Au core. [ABSTRACT FROM AUTHOR]

In this work, we introduce a novel ZnTe/quinhydrone (ZnTe/QH) nanocomposite as an excellent catalyst for electro-oxidation of ethanol in alkaline medium. The ZnTe semiconductor nanorods were synthesized by a novel chemical route. The synthesized product was characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), FT-IR spectroscopy, and cyclic voltammetry techniques. Then, this product along with quinhydrone were used for the electrocatalytic oxidation of ethanol in alkaline medium. The ZnTe/QH/GCE showed a higher electrocatalytic activity toward ethanol oxidation. The performance of catalyst was evaluated by electrochemical measurements such as cyclic voltammetry and electrochemical impedance spectroscopy using the three-electrode system. Furthermore, the ZnTe/QH/GCE displayed a higher stability with 93% retention of the initial current density after 6000 s in long term current-time curve. This newly prepared ZnTe/QH nanohybrid could be a promising anodic catalyst for the direct ethanol fuel cells (DEFCs) application. Image 1 • Synthesized a novel catalyst ZnTe/QH by ultrasonic assisted strategy. • ZnTe/QH catalyst used as a low cost alternative to Pt and Pd catalysts. • ZnTe/QH catalyst has large j f /j b value, high activity and stability. [ABSTRACT FROM AUTHOR]

In this work, we prepared four electrocatalysts based on trimetallic PtPdNi nanoparticles on different carbon supports, i. e., i) two activated carbons produced from biomass, ii) micro‐mesoporous carbon synthesized by the nanocasting method, and iii) commercial carbon black. The electrocatalytic activity of the prepared materials was tested in the electro‐oxidation of ethanol in alkaline medium. Well‐distributed nanoparticles with sizes in the range of 3.5–5.2 nm were obtained through galvanic replacement. The bulk Pt, Pd and Ni contents were about 65, 25 and 15 at. %, measured by EDX and ICP‐AES. By XPS the surface Pt : Pd atomic ratios were in the range of 1.82–2.2. Electrochemical experiments showed that the trimetallic nanoparticles deposited over micro‐mesoporous carbon material exhibit the highest electrochemical activity towards ethanol electro‐oxidation in alkaline medium. Results showed that both synthetic carbon and biomass‐derived carbon are suitable materials to support electrocatalysts in low‐temperature fuel cells. [ABSTRACT FROM AUTHOR]

Herein, the catalysts contained metal- and nitrogen-doped carriers were synthesized by a novel and simple method. The synthesized catalysts with different particle size and distribution were controlled by adjusting the ratio of urea and metal salt solution. The morphology, microstructure, and particle distribution of the catalysts were confirmed by transmission electron microscopy and X-ray powder diffraction. The catalytic performance of the catalysts was tested by cyclic voltammetry (CV) and amperometric i-t curves. It was found that the urea content had an influence on the distribution of metal particles and the size of the nanoparticles. More catalyst active sites were formed on the surface of the catalyst due to that many nitrogen-based functional groups were formed on the surface of the carrier. Compared with other samples, catalyst with urea amount of 100 mg (Pt2Ni3/C–N3 samples) possessed small particle size and uniform distribution, which exhibited higher electrocatalytic activity and stability, and the maximum of forward anodic peak reached 1454 mA mg−1. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Carbon dioxide (CO 2) is considered a useful greenhouse gas that can be captured and be used in the electro-syntheses of useful chemicals or fuels. On the other hand, there's also a tremendous interest on ethanol beneficiation as it is largely produced from crops, and it is regarded as a potential candidate for low temperature fuel cell applications. Although ethanol possesses good advantages, its resistant to oxidation poses a threat. The main objective of the study is to synthesis bio-inspired metal oxide–support catalyst which will help enhance the activity, efficiency and selectivity of Pd catalyst in CO 2 reduction, Fuel cell performance and ethanol oxidation. Here, Pd nanoparticles were supported on NiO/C through a green facile one-step process using pomegranate peel extracts as reducing agent. A series of characterizations were carried out to provide proof for and to quantify the presence of Pd, Ni, O and C in the prepared sample. Microscopic methods confirmed the successful preparation of pure NiO/C and (%5 Pd) Pd-NiO/C, evident by the key elemental components, mixed nanostructures and co-existence of Pd and NiO/C. The resultant Pd-NiO/C nanocatalyst revealed higher activity towards the oxidation of ethanol and that the nanocatalyst is more tolerant to poising by intermediate oxidation species. Enhanced cell performance with current and power densities of 66 mA cm−2 and 26 mW cm−2 relative to the commercial Pd/C were obtained under passive conditions at 1 M ethanol in 1MKOH. In addition, the nanocatalyst showed good selectivity to HCOOH with enhanced current efficiencies of 45%. [ABSTRACT FROM AUTHOR]

Abstract Due to the depletion of fossil fuels and severe environmental pollution problems, the urgent demand for clean and sustainable energy sources is constantly emphasized. In recent decades, platinum (Pt)-based fuel cells have achieved tremendous advances as a green energy source, but there is still a need to further improve energy production efficiency in order to realize practical applications. Conventional Pt electrocatalysts are usually insufficient in catalytic activity and the selectivity of electrochemical reactions due to sluggish kinetics and surface poisoning. In contrast, metal alloy nanocatalysts exhibit exceptional electrocatalytic performance on fuel cells, more than pure Pt catalysts, owing to the synergistic effect by systematic modification of the surface geometry and electronic structure of the catalytically active metal component. This review provides overviews and advances in the applications of metal alloy nanohybrid particles enabling the improvement of electrocatalytic efficiency and discusses the challenges and outlooks in the fields of green energy production based on metal alloy nanocatalysts. Graphical abstract Synergistic effects (d -band shift, surface-lattice strain and surface-defects formation) of metal alloy nanocatalysts for the improvement of electrochemical activity. fx1 Highlights • Metal alloy nanocatalysts exhibit exceptional electrocatalytic activity on fuel cell. • Advances of metal alloy particles enhancing electrocatalytic activity are reviewed. • Outlooks in the field of fuel cell based on metal alloy nanocatalysts are discussed. [ABSTRACT FROM AUTHOR]

Abstract We report the study of the oscillatory electro-oxidation of ethanol on platinum surfaces under galvanostatic conditions. In order to correlate the features of potential oscillations with the surface chemistry of different adsorbates, we use in situ surface-enhanced infrared absorption spectroscopy in the attenuated total reflectance mode (ATR-SEIRAS). Results show that the maintenance of the oscillatory state does not seem to be particularly correlated with the CO surface coverage, conversely to what is observed for methanol. Indeed, our data suggest that oscillations continue as long as the coverage of molecular fragments from ethanol (regardless its nature) remain within a range that allows the coexistence of surface oxides (responsible for the activation of the surface throughout oxidation steps). Our results throw some light in the oscillatory kinetics of ethanol by establishing an unequivocal correlation between the features of the galvanostatic oscillations and the dynamics of the adsorbed species. Highlights • The oscillatory electro-oxidation of ethanol on platinum was studied by ATR-SEIRAS. • The oscillation pattern is different from that observed for methanol. • ATR-SEIRAS show that the oscillation persists even in the absence of CO. • CO cannot explain the sustenance of oscillatory loops. • Species containing carbonyl seem to be co-responsible for the oscillations. [ABSTRACT FROM AUTHOR]

Abstract The Pd/C, PdRh(50:50)/C and PdSn(50:50)/C nanomaterials were used as electrocatalysts for ethanol (EtOH) oxidation in Direct Ethanol Fuel Cell (DEFC) in an alkaline medium. This work aims to provide a complete physical characterization of the nanomaterials, elucidate the bifunctional mechanism concerning ethanol oxidation reaction and understand the influence of carbon – metal bonding in the electrochemical activity. These nanomaterials were investigated by X-ray photoelectron spectroscopy (XPS) and revealed that the atomic percentage of the surface is different of those obtained by Energy Dispersive X-ray spectroscopy (EDS). Raman spectroscopy showed a bonding between palladium and carbon atoms which can play a decisive role in the performance of the materials. Attenuated Total Reflectance technique coupled to the Fourier Transform Infrared spectroscopy (ATR-FTIR) made possible to investigate the oxidation products originated by the ethanol oxidation, and all the electrocatalysts showed the presence of acetaldehyde, carbonate ions, acetate and carbon dioxide, suggesting that the mechanism of oxidation is incomplete. Among all the nanomaterials studied, PdSn(50:50)/C showed the best electrochemical and Fuel Cell's results. It is about 33% better than Pd/C. The micrographs obtained by Transmission Electron Microscopy (TEM) revealed some agglomerate regions, but they are consistent with the literature data. Highlights • Pd-C bonds show a significant effect toward EOR. • XPS was more surface sensitive than EDS concerning metal oxidation states. • PdSn(50:50)/C has a better performance in DEFC than Pd/C and PdRh(50:50)/C. [ABSTRACT FROM AUTHOR]

The addition of H 2 SO 4 to the anolyte feeding solution for the electrochemical reforming of ethanol has been studied in terms of activity and stability for hydrogen production in a PEM electrolysis cell. Five equivalent MEAs based on commercial Pt-Sn/C and Pt/C as anode and cathode materials, respectively, and a Nafion membrane, have been prepared and tested to optimize the addition of the H 2 SO 4 . Results demonstrated that the addition of an optimal H 2 SO 4 concentration (ethanol 4 mol L −1 and 0.01 mol L −1 H 2 SO 4 ) enhances the electrocatalytic activity and stability of the MEA by decreasing the energy requirements for hydrogen production. According to impedance spectroscopy experiments, this improvement is caused by a decrease in the anodic charge transfer resistance, probably due to an increase in the number of contact triple points (electrolyte/catalyst particles/electronic support). However, the addition of a higher H 2 SO 4 concentration (0.05 mol L −1 ) induced the dissolution of the Pt-Sn/C anodic catalyst causing a severe degradation of the MEA. Therefore, the optimal addition of H 2 SO 4 , which is not consumed during the electrochemical reforming experiments, may be of great practical importance for using this technology for the renewable hydrogen production from real bioethanol streams. [ABSTRACT FROM AUTHOR]

Ethanol has attracted attention as a renewable fuel for application in electrochemical reformers, for the production of hydrogen, and in fuel cells. The electro-oxidation of ethanol, however, faces a central drawback related to the difficulty for the C C bond cleavage, which is required for its complete electro-oxidation to CO 2 . Thus, the efficiency has to be increased and this is the main challenge for the use of ethanol as a fuel in such devices. In this study, the ethanol electro-oxidation was studied at metallic nanoparticle/Aquivion® solid-state interfaces. The nanostructured electrocatalysts were formed by Pt/C, Rh/C, Sn/Pt/C, and Sn/(PtRh)/C nanoparticles, and the electrocatalysis was tested at temperatures ranging from 25 to 140 °C. Potentiostatic and potentiodynamic measurements showed a marked effect of the temperature on the electrocatalytic activity and, principally, on the stability, due to lower poisoning by adsorbed reaction intermediates above 100 °C. By using a new setup for coupling the solid-state electrolyte cell with a DEMS (Differential Electrochemical Mass Spectrometry) equipment, with a proper calibration, it was possible to determinate the faradaic efficiency of ethanol electrochemical oxidation to CO 2 at each studied condition. The results showed that the CO 2 current efficiencies ( CCE ) increased from approximately zero, at 25 °C, to 54.0, 44.1, 22.7, and 13.1% for Rh/C, Pt/C, Sn/(PtRh)/C (1:3), and Sn/Pt/C (1:3), respectively, at 120 °C, under potentiostatic conditions. The impact of the temperature was more prominent for Rh/C, and this was associated to its ability for ethanol dehydrogenation in the methyl group, resulting in the formation of adsorbed oxametallacycle species, that facilitates the direct cleavage of the C C bond, this step being more rapid at 120 °C than at ambient temperature. [ABSTRACT FROM AUTHOR]

An in-situ composite methodology was first proposed to prepare carbon supported PtNix (X = 1, 3, 1/3) via online reaction, nucleation and growth of nanocrystals (NCs) on carbon support along the microfluidic channel. Uniform dispersed ultra-small PtNi X NCs (1 nm–3 nm) with high surface exposed Pt atoms and enhanced nanocrystal-carbon interface interaction can be constructed. The annealed nanocomposites with a Pt/Ni ratio of 1/3 exhibit a mass catalytic activity of 7.6 times higher than the commercial Pt/C nanocatalysts in the ethanol oxidation reaction. The chronoamperometry measurement indicates that their mass activity still retains 3.6 times of the commercial Pt/C nanocatalysts at 4000 s. Moreover, PtNi 3 /C nanocatalysts have the highest tolerance to CO poisoning according to CO stripping measurements. [ABSTRACT FROM AUTHOR]

The efficiency of direct ethanol fuel cells suffers from the partial oxidation of ethanol into acetic acid as opposed to the complete oxidation of this fuel to CO 2 . Herein, we support the quest for a selective catalyst for ethanol electro-oxidation to CO 2 , building on our previous mechanistic hypothesis based on experimental insight and DFT computations. We derive a simple descriptor of the expected selectivity towards full oxidation, Ω, as a function of the adsorption energy of atomic C and O. Three different families of catalyst surfaces are screened using this descriptor: monometallics, bimetallics and conducting metal oxides, totaling to 600 surfaces. In agreement with available experimental data, no single metal surface is more selective for total oxidation than platinum and palladium. While the selected conducting oxides were not predicted to be selective towards splitting the C C bond, structurally-controlled monometallics (such as Pd(100)) or some bimetallics (Pd 3 Ag) are found to be competitive with the most stable facet, (111), of Pd and Pt. Despite this very extensive screening, no very promising catalyst has been identified. This highlights the need to identify catalysts for acetate oxidation or to exploit support effects and electrolyte engineering to profit from the full power of direct ethanol fuel cells. [ABSTRACT FROM AUTHOR]

Ethanol oxidation reaction (EOR) on Pd 2 Ru/C and Pd/C catalysts in alkaline media is studied comprehensively by cyclic voltammetry, chronoamperometry, in situ FTIR, single fuel cell test and electrochemical impedance spectroscopy measurements. The results show that, as compared to Pd/C, Pd 2 Ru/C favors acetaldehyde formation and hinders its oxidation. Based on X-ray absorption data, which evidence that Ru promotes a larger electronic vacancy of the Pd 4d band, it is expected that the formation of adsorbed ethoxy is favored on Pd 2 Ru/C and followed by its oxidation to acetaldehyde facilitated by oxygenated species provided by Ru. In contrast, acetaldehyde oxidation is more difficult on Pd 2 Ru/C than on Pd/C likely because the adsorption energy of the reactive species is increased. We also show that the performance of Pd 2 Ru/C anode in alkaline direct ethanol fuel cell (ADEFC) is initially better but degrades much more rapidly than that with Pd/C anode under the same test conditions. The degradation is demonstrated to result from the accumulation of large amounts of acetaldehyde, which in alkaline media forms dimers by the aldol condensation reaction. The dimers tend to be responsible for blocking the active sites for further ethanol oxidation. This comprehensive study provides new understandings of the roles of Ru in Pd 2 Ru/C for EOR in alkaline media, unveils the causes of the performance degradation of fuel cells with Pd 2 Ru/C and demonstrates that initial good performances are not necessarily a valid criterion for selecting appropriate anode catalysts for ADEFC applications. [ABSTRACT FROM AUTHOR]

The stability testing of three different synthesized PtxSn1 − x/C anodic catalysts has been demonstrated for the renewable generation of hydrogen via the electrochemical reforming of ethanol in a proton exchange membrane (PEM) electrolysis cell. Three Pt-Sn anodic catalysts with different nominal Pt:Sn ratios of 60:40, 70:30, and 80:20 atomic (at.) % were synthetized and characterized by the means of electrochemical tests and XRD. Among them, the Pt-Sn anodic catalyst with 70:30 at. ratio showed the highest electrochemical active surface area (ECSA) and highest electrochemical reforming activity, which allowed the production of pure H2 with the lowest electrical energy requirement (below 23 kWh·kgH2−1). The stability of the system was also demonstrated through a long-term chronopotentiometry experiment of 48 h in duration. The potential for practical use and coupling this technology with renewable solar energy, a number of cyclic voltammetry tests (with a low scan rate of 0.19 mV·s−1) were also carried out. These experiments were performed by simulating the electrical power produced by a photovoltaic cell. This test showed good stability/reproducibility of the MEA and, hence, a suitable integration between the two technologies for the sustainable energy storage in the form of hydrogen.ᅟGraphical Abstract [ABSTRACT FROM AUTHOR]

Abstract: In this work, we prepared a polymer gel based on poly (acrylic acid) partial potassium salt (PAA‐K) for its use as an electrolyte in the ethanol electro‐oxidation. In addition, we synthesized PdxAgy materials by varying the metallic ratio through differential pulse amperometry (DPA). These materials showed particle sizes ranging from 40 to 60 nm, and their compositions were Pd75Ag25, Pd60Ag40, and Pd50Ag50, as determined by X‐ray fluorescence. Electrocatalytic evaluation of ethanol oxidation in aqueous electrolyte at 1.0 M ethanol resulted in the following activity trend: Pd60Ag40>Pd50Ag50>Pd75Ag25≥Pd, where Pd60Ag40 showed the highest current density with 102.6 mA mg−1 Pd. In the PAA‐K gel electrolyte, Pd60Ag40 also achieved the highest peak current density (7.5 mA mg−1 Pd). Additionally, Pd60Ag40 maintained almost the same oxidation potential (−0.41 V vs. NHE) in aqueous and gel electrolytes, but the current density decreased 13.7‐fold owing to the high viscosity of PAA‐K electrolyte (∼400 cP). [ABSTRACT FROM AUTHOR]

Palladium nanoparticles supported on carbon Vulcan XC72 (Pd/C) and on phosphorus-doped carbon (Pd/P-C) were prepared by an alcohol reduction process. X-ray diffractograms of Pd/C and Pd/P-C showed the typical face-centered cubic (fcc) structure of Pd. The crystallite sizes of Pd fcc phase were around 8 nm for both samples. X-ray photoelectron spectroscopy revealed to Pd/C and Pd/P-C that Pd was found predominantly in the metallic state and to Pd/P-C, the presence of P increases the amount of oxygen on the electrocatalyst surface. The activity and stability of the electrocatalyts for ethanol electro-oxidation in alkaline medium was investigated by cyclic voltammetry and chronoamperometry experiments. The peak current density on Pd/P-C was 50% higher than on Pd/C, while the current density measured after 30 min at − 0.35 V vs. Hg/HgO was 65% higher on Pd/P-C than on Pd/C. The enhancement of the catalytic activity of Pd/P-C electrocatalyst might be related to the presence of higher amounts of oxygen species on the surface, which could contribute to the oxidation of intermediates formed during ethanol electro-oxidation process. [ABSTRACT FROM AUTHOR]

A PtCu electrocatalyst was synthesized using a galvanic displacement route obtaining nanoparticles with a semi-spherical morphology and an average size of 4 nm, supported on carbon black (Vulcan). The crystallographic characterization by X-ray diffraction showed a certain degree of Pt Cu alloying. The electrocatalytic activity of the prepared electrocatalyst for the electro-oxidation of ethanol in alkaline media was investigated. A 2-fold increase of the peak current density and a negative shift of the potential were recorded in half-cell experiments for the bimetallic catalyst compared to a commercial Pt/C. The presence of Cu promotes ethanol oxidation in alkaline electrolyte by hindering the Pt H adsorption at low overpotentials. Additionally, the PtCu electrocatalyst was used as anode in an anion-exchange-membrane direct ethanol fuel cell (AEM-DEFC) exhibiting about 2-fold higher power density than the benchmark Pt/C. [ABSTRACT FROM AUTHOR]

A new catalysts electrode was prepared by in situ controllable deposition of Pd shell layer on the gas diffusion layer (GDL) supported Ni(OH) 2 nanoparticles using atomic layer deposition (ALD) technology. High resolution transmission electron microscope confirmed that the Ni(OH) 2 core was coated by several atomic layers of Pd. The core-shell Ni(OH) 2 @Pd catalysts with different thickness of Pd shell are easily prepared by controlling ALD cycle. Electrochemical tests showed that the 100-Ni(OH) 2 @Pd/GDL catalyst prepared via 100 ALD cycles presented the highest catalytic activity for ethanol electro-oxidation reaction (EOR). The peaking current density of Ni(OH) 2 @Pd/GDL was 1439 mA mg Pd −1 , which was about 2.75 times as high as that of Pd/GDL (522 mA mg Pd −1 ). The shift in binding energy of the XPS peak of Pd in Ni(OH) 2 @Pd catalyst confirmed the strong interaction between the Pd shell and the Ni(OH) 2 core. We suggested that the high catalytic activity of Ni(OH) 2 @Pd/GDL catalyst layer may be due to following factors: high Pd dispersion arising from the core-shell structure, high Pd utilization because of the in situ deposition of Pd on catalyst layer and the interaction between the Pd shell and the Ni(OH) 2 core. Herein, the ALD technology exhibits a promising application prospect for preparing core-shell structure and precisely controlling shell thickness of nano-composite as an electro-catalyst toward EOR. [ABSTRACT FROM AUTHOR]