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Direct ethanol fuel cells (DEFCs) play an indispensable role in the cyclic utilization of carbon resources due to its high volumetric energy density, high efficiency, and environmental benign character. However, owing to the chemically stable carbon‐carbon (C─C) bond of ethanol, its incomplete electrooxidation at the anode severely inhibits the energy and power density output of DEFCs. The efficiency of C─C bond cleaving on the state‐of‐the‐art Pt or Pd catalysts is reported as low as 7.5%. Recently, tremendous efforts are devoted to this field, and some effective strategies are put forward to facilitate the cleavage of the C─C bond. It is the right time to summarize the major breakthroughs in ethanol electrooxidation reaction. In this review, some optimization strategies including constructing core–shell nanostructure with alloying effect, doping other metal atoms in Pt and Pd catalysts, engineering composite catalyst with interface synergism, introducing cascade catalytic sites, and so on, are systematically summarized. In addition, the catalytic mechanism as well as the correlations between the catalyst structure and catalytic efficiency are further discussed. Finally, the prevailing limitations and feasible improvement directions for ethanol electrooxidation are proposed. [ABSTRACT FROM AUTHOR]

In this study, the electro-oxidation reaction of ethanol over Pd–Cu supported on Cu porphyrin (TPPCu) was investigated. The catalyst was synthesized using the microwave-assisted polyol method and physicochemically characterized by XRD, XPS, SEM, EDS, TEM, EDAX, UV–Vis, FTIR, and RBS. A Cu-enriched catalyst with Cu3Pd, Pd,Cu, and TPPCu phases was identified using XRD and XPS. However, according to the RBS results, the catalytic surface was enriched with Pd, indicating that the interaction between TPPCu and Pd–Cu allowed the presence of Pd on the surface, thus enhancing the catalytic response of the material. This synthesis prevented the deprotonation of porphyrin on the electrocatalyst, as confirmed by XPS analysis. Electrochemical studies based on cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the response of the catalyst to variations in the scan rate and increasing ethanol concentration. The electrochemical response of PdCu/TPPCu improved with an increasing number of cycles, indicating improved mass transport, thus improving its electrochemical response and tolerance to CO contamination. This catalyst exhibited a high electroactive surface area of 49.4 m2/g, which could be related to the presence of TPPCu as a support. The behavior of the catalyst on the anode of a fuel cell fed with ethanol, bioethanol, and bioethanol residues was evaluated. [ABSTRACT FROM AUTHOR]

In this study, an iridium-oxide-layer-deposited Pt surface (IrOx–Pt) was explored as a catalyst for the ethanol oxidation reaction (EtOR) in an alkaline medium. To fabricate the catalyst, the cleaned Pt surface was scanned from 0 V to +1 V vs. Ag/AgCl (sat. KCl) in an Ir2O3·xH2O colloidal suspension for 10 continuous cycles. The cyclic voltammogram recorded in the 0.1 M NaOH solution corroborated the presence of IrOx as it showed the appearance of a distinct redox pair on the Pt surface, with Epa at −0.31 V and Epc at −0.27 V. Energy-dispersive mapping verified the uniform deposition of IrOx on Pt, and X-ray photoelectron spectroscopy showed that IrOx contained both IrIII and IrIV species. The results of the cyclic voltammetry analysis indicated that the activity of the pure Pt catalyst towards the EtOR was approximately 1.3 times greater than that of IrOx–Pt. However, the CO tolerance of the Pt catalyst was roughly 3.5 times lower than that of IrOx–Pt. The results of the stability test indicated that the current density associated with EtOR on the IrOx–Pt electrode experienced a decrease of approximately 18% with a standard deviation of 1.15% after 500 consecutive cycles. In contrast, the Pt electrode exhibited a decrease in activity of nearly 50% with a standard deviation of 1.53% under similar experimental conditions. The study of scan rate dependent voltammograms revealed that the electrode reaction was limited by mass transfer. [ABSTRACT FROM AUTHOR]

Direct Ethanol Fuel Cells (DEFCs) are important clean energy conversion systems which can reach high energy densities using inexpensive and non-toxic fuels. One of the main obstacles to using DEFC systems is the high cost of platinum or platinum-alloy electrodes traditionally used in these systems. However, other less expensive co-catalysts, e.g., transition metal complexes, can be used to partially replace platinum or platinum-alloys in Pt-based electro-catalysts. The aim of this study is to describe and analyze the use of a new uranyl salen-type complex as co-catalyst in ethanol electro-oxidation. To this end, the structural and spectroscopic properties of the co-catalyst in question was investigated by single-crystal X-ray diffraction, DFT, elemental analysis (CHN), FTIR, UV-Vis, and 1H and 13C NMR. Cyclic voltammetry indicated a quasi-reversible redox pair at 0.97/0.69 V (E1/2 = 0.83 V) along with an anodic process at 1.14 V, both associated to the phenolate/phenoxyl radical couple. Six PtSn-based catalysts were produced by varying the PtSn:uranyl complex molar ratio. The ethanol oxidation reaction was investigated in acidic media via cyclic voltammetry and chronoamperometry. Direct scanning of the samples indicated that the peak-current density for the 6 : 1 PtSn/C : [UO2(3-OMe-c-salcn)H2O] catalyst was higher than that for other catalyst ratios. Moreover, as compared to the pure PtSn catalyst, 6 : 1 PtSn/C : [UO2(3-OMe-c-salcn)H2O] exhibited better catalytic activity in ethanol electro-oxidation reaction (EOR); it decreased the onset potential during ethanol oxidation. In addition, this catalyst exhibited peak-current densities about 2.3 times that of PtSn/C. pH affected the catalytic system performance, which decreased as pH increased (maximum efficiency at pH 0.3). Ethanol oxidation catalyzed by 6 : 1 PtSn/C : [UO2(3-OMe-c-salcn)H2O] was also investigated using cyclic voltammetry and chronoamperometry at different ethanol concentrations, indicating that the EOR peak increased as ethanol concentration increased. [ABSTRACT FROM AUTHOR]

In this work, to prepare nanostructured and porous Fe/Pd–Fe bimetallic catalysts, the iron coating is applied firstly onto the copper substrate by the electrochemical deposition method. Subsequently, iron-zinc alloy coating is deposited on the underlayer iron. Eventually, by immersing this alloy coating in an alkaline solution containing palladium ions, the palladium will replace the zinc, resulting in porous Fe/Pd–Fe catalysts. The X-ray diffraction (XRD) technique was used for the characterization of the physical properties of the as-prepared electrocatalysts. Their electrocatalytic activity was studied by electrochemical methods such as cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The XRD results showed that the zinc element was the main component of the Fe/Zn-Fe alloy and was replaced by palladium as a result of leaching-galvanic replacement. The electrochemical investigations showed that a new porous Fe/Pd-Fe bimetallic catalyst had higher electro-catalytic activity and stability than pure Pd and Fe electrodes for ethanol electro-oxidation in alkaline media. The superiority of the Fe/Pd–Fe catalyst is related to the high surface area and a synergistic effect between Fe and Pd in Fe/Pd–Fe catalysts. Therefore, the nanostructured Fe/Pd–Fe catalysts can be proposed as potential anode materials for alkaline ethanol fuel cells. A new porous Fe/Pd–Fe bimetallic catalyst shows higher electro-catalytic activity and stability than pure Pd and Fe electrodes for ethanol electro-oxidation in alkaline media. The superiority of the Fe/Pd–Fe catalyst is related to the high electrochemical surface area and a synergistic effect between Fe and Pd in Fe/Pd–Fe catalysts [ABSTRACT FROM AUTHOR]

In this work, the synergism between the nano nickel particles and its carbon xerogel support, CX, together with their graphite substrate, G, leads to an efficient Nickel/CX/G electrode for electrocatalysis of ethanol oxidation reaction, EOR. The preparation conditions are optimized. The optimum electrode is made of 6 % weight of Ni doped in CX matrix and drop‐casted on a graphite surface, Ni‐6/CX/G. The catalyst structure and morphology are investigated using XRD, SEM, TEM and FTIR techniques. The electrochemical activity towards EOR is tested in 1 M NaOH+1 M Ethanol solutions by cyclic voltammetry combined with a rotating ring disk electrode. The optimum electrode shows an oxidation peak current density value of 5925 A.gNi-1 ${{\rm A}.{{\rm g}}_{{\rm N}{\rm i}}^{-1}}$ and considerable stability. This electrode may serve as a good candidate for the anode in the Direct Alkaline Ethanol Fuel Cell, DAEFC. [ABSTRACT FROM AUTHOR]

The synthesis of Pt−Rh alloy nanowires (NWs) using straightforward methodologies remains a challenge. Here, carbon‐supported Pt and Pt−Rh nanowire catalysts were synthesised by chemical reduction at room temperature, without using surfactants or templates. The method of synthesis used yielded Pt/C NWs and a mixture of nanowires with some nanoparticles for the Pt−Rh/C catalysts (characterised using XRD, TEM, EDX, XPS, and XAS). The nanoparticles form due to differences in the surface energy and atomic radius between Pt and Rh. The binary NWs are found to be more active towards ethanol oxidation than the commercial Pt/C reference catalyst. Additionally, the Pt−Rh/C NW catalyst displays a specific activity 2.5‐fold higher than the Pt/C NWs and Pt/C reference catalysts after 15 min of chronoamperometric tests (at 0.5 V vs RHE). Thus, the synthesised carbon‐supported Pt NWs and Pt−Rh nanowires‐nanoparticles are promising alternatives for direct ethanol fuel cell anodes. [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]

Rational design and synthesis of superior electrocatalysts for ethanol oxidation is crucial to practical applications of direct ethanol fuel cells. Here, we report that the construction of Pd-Zn dual sites with well exposure and uniformity can significantly improve the efficiency of ethanol electro-oxidation. Through synthetic method control, Pd-Zn dual sites on intermetallic PdZn nanoparticles, Pd-Pd sites on Pd nanoparticles and individual Pd sites are respectively obtained on the same N-doped carbon coated ZnO support. Compared with Pd-Pd sites and individual Pd sites, Pd-Zn dual sites display much higher activity for ethanol electro-oxidation, exceeding that of commercial Pd/C by a factor of ~24. Further computational studies disclose that Pd-Zn dual sites promote the adsorption of ethanol and hydroxide ion to optimize the electro-oxidation pathway with dramatically reduced energy barriers, leading to the superior activity. This work provides valuable clues for developing high-performance ethanol electro-oxidation catalysts for fuel cells. Rational design and synthesis of superior electrocatalysts for ethanol oxidation is crucial to practical applications of direct ethanol fuel cells. Here, authors report the construction of Pd-Zn dual sites with well exposure and uniformity can improve the efficiency of ethanol electro-oxidation. [ABSTRACT FROM AUTHOR]

Carbon-supported PtSnCu/C, Pt3Sn/C, Pt3Cu/C and Pt/C electrocatalysts were synthesized by chemical reduction of metal precursors in ethanol reflux. These materials were characterized by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and applied to the ethanol electro-oxidation in acidic medium. The reaction kinetics was studied by cyclic voltammetry and the mechanism was explored by in situ Fourier transform infrared spectroscopy (FTIR). The investigated materials presented chemical composition close to the nominal ones. XRD results indicated the formation of solid solution of Pt and Cu and/or Sn in the bi and tri-metallic materials. The particle size distribution was narrow with mean particle size of around 3 nm. A homogeneous distribution of the nanoparticles over the carbon support was evidenced. The investigated catalysts were active towards the ethanol oxidation reaction in acidic medium and led to the formation of CO2 and carbonyl compounds, as evidenced by FTIR. PtSnCu/C and Pt3Cu/C started to produce CO2 at 0.70 V vs. RHE, while this product was detected only at 0.75 V and 0.80 V vs. RHE on Pt and Pt3Sn/C, respectively, suggesting that Cu improves the dissociative adsorption of ethanol. [ABSTRACT FROM AUTHOR]

• Synthesis of Pt-Sn-Co core-shell cubic nanoparticles. • Outstanding performance toward the ethanol oxidation reaction. • Mechanistic and structural insights by in situ and operando techniques. • High amount of C1 (CO 2) and C2 (acetic acid/acetaldehyde) products during EOR. • High ability to remove adsorbed CO from the Pt surface. Direct ethanol fuel cells are among the most promising clean electrochemical power sources. Nevertheless, the high cost and low efficiency of the Pt-based catalysts hinder their commercialization. Here, Pt-Sn-Co nanocubes with a Pt- and Sn-rich shell show improved performance towards the electrochemical ethanol oxidation reaction (EOR). Mechanistic and structural insights were obtained by synergistically combining different in situ and operando spectro-electrochemical techniques, including electrochemical mass spectrometry, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. In particular, electrochemical conditioning and EOR were found to induce Sn leaching from the core and shell, leading to electrochemically-accessible Pt sites adjacent to partially-oxidized Sn sites on a Pt 3 Co-like core. The increased activity of the Pt-Sn-Co nanocubes was assigned to the formation of a higher amount of C 1 (CO 2) and C 2 (acetic acid/acetaldehyde) products during EOR as well as to their high ability to remove adsorbed CO from the Pt surface when compared to similarly-sized cubic Pt-Sn or Pt NPs. Beneficial strain and ligand effects are combined here through a catalyst design resulting in adjacent Pt and Sn sites at the overlayer on top of a Pt 3 Co alloy core. [ABSTRACT FROM AUTHOR]

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]

Direct alkaline ethanol fuel cells (DAEFCs) have attracted great attention as one of the most promising portable energy systems. In this work, we report a novel and facile method to prepare PdAg/xCeO2/C hybrid nanostructured anode catalysts without reducing agents or surfactants. The microstructure and morphology of the as-synthesized nanocatalysts were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and X-ray photon spectroscopy (XPS) techniques. Furthermore, the electrochemical performance of the resultant catalysts was studied using cyclic voltammetry (CV) and chronoamperometry (CA) measurements. Among the different compositions of PdAg/xCeO2/C catalysts, PdAg/30CeO2/C showed the highest performance for ethanol electro-oxidation reaction (EOR) in the alkaline medium. Such an excellent performance for the EOR indicates that the as-synthesized PdAg/30CeO2/C catalyst could be potentially used as a high performance anode catalyst in DAEFCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pt-Ag/AC bimetallic catalyst synthesis via a gradual reduction method. • The synergistic effect was revealed between Pt and Ag for EOR. • Pt-Ag/AC has good cyclic stability: activity retention of 65.2% till 1000 cycles. • The anti-poisoning property of Pt-Ag/AC is impressive with j f /j b ratio of 3.5. • A detailed kinetic study is provided for EOR on Pt/AC (2 wt%) and Pt-Ag/AC catalysts. Due to the scarcity of fossil fuels and their severe environmental consequences, the development of high-efficiency energy conversion devices such as fuel cells (FCs) has gained considerable attention. The specific energy conversion efficiency of FC is highly influenced by the activity of the electrocatalysts. Platinum (Pt) is widely used as an electrocatalyst due to its high activity and stability, but high cost and depletion of resources hinder its commercialization. One of the workable strategies for the practical application of Pt is to reduce its content by alloying with non-precious metals and simultaneously maintain its electrochemical performance. In this context, we developed a low Pt-loaded Pt-Ag/AC alloy electrocatalyst. The electrocatalytic activity and kinetics of the as-synthesized catalyst were evaluated by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) using the three-electrode electrochemical workstation at room temperature. The electrocatalytic investigations reveal that the resultant AC-supported Pt-Ag with Pt: Ag = 1.8:2.3 at% has higher activity i.e., 32.7 mA cm−2 as compared to that of Pt/AC (20.8 mA cm−2) in an alkaline electrolyte and makes it an efficient electrocatalyst for the electro-oxidation of ethanol. The electron donation from Ag to Pt during the alloying process helps in weakening the interaction with CO and other intermediate species, thereby lowering their binding and poisoning effect on the surface, which may partly be responsible for the improved catalytic performance of Pt-Ag/AC. The activated carbon (AC) support also favors charge transport by reducing ohmic resistance. The cyclic stability studies also reveal that Pt-Ag/AC performs significantly better than Pt/AC with a current retention of 65.2 % and 48.3 % till 1000 cycles, respectively. Therefore, alloying Pt with earth-abundant Ag under rational composition provides optimized surface and electronic properties that result in improved ethanol electro-oxidation activity while reducing the utilization of precious noble metals. [ABSTRACT FROM AUTHOR]

[Display omitted] • Composition engineering was adopted to design Pt x RhRu/CNTs EOR catalysts. • Experiments conform the predictions by DFT and Pt 4 RhRu/CNTs performed the best. • The optimal EOR route is changed on Pt x RhRu, further enhancing C 1 selectivity. • The poisoning is declined by both weakening molecular bonding and providing *OH. The practice of direct ethanol fuel cells (DEFCs) is hindered by insufficient activity of anode Pt-based catalyst for ethanol oxidation reaction (EOR), while alloying Rh and Ru to Pt is hopeful to solve the problem by simultaneously enhancing C C cleavage and decreasing poisoning; and Ru owning better stability and activity than usually doped Sn in alkaline electrolyte. Nevertheless, Pt-Rh-Ru catalysts were rarely reported. In this work, to avoid random trials, the "composition engineering" strategy was applied to design Pt x RhRu catalysts. The optimal x range was predicted by DFT. Then, carbon nanotubes supported Pt x RhRu ultrafine nanoparticles (Pt x RhRu/CNTs) were synthesized and characterized. The synthetic mechanism was also studied. EOR tests show that, in line with the forecast, Pt 4 RhRu/CNTs (∼1.9 nm) exhibit the highest activity (5.85 mA·cm−2), 6.97 times of commercial Pt/C, and higher than most reports. The selectivity, stability and durability are also excellent. DFT analysis reveals the role of Pt-Rh-Ru site for the first time, that the optimal route on Pt x RhRu is changed. New route clearly enhances complete ethanol oxidation and reduces poisoning. Bifunctional mechanism on Pt-Rh-Ru site was also confirmed. This study may provide new perspective for material design; the products are also promotive for DEFCs into practice. [ABSTRACT FROM AUTHOR]

• MD-PtCo/C electrocatalyst is prepared from Pt-replaced Prussian blue analogues. • It possesses ultra-low Pt load (0.95 wt.%) with small particle (4.5 ± 0.9 nm). • It has good EOR activity (840 mA mg−1 Pt) than that of Pt/C. Currently, designing and preparing low-cost and high-efficiency electrocatalysts still remains of huge impediment for direct ethanol fuel cells (DEFCs). In this work, by leveraging the unique superiority of Co 3 [Co(CN) 6 ] 2 (Prussian blue analogues, PBA) precursor, we used Pt4+ to replace partial dispersed Co2+ in Co 3 [Co(CN) 6 ] 2 and a metal–organic framework (MOF) derived PtCo electrocatalyst (MD-PtCo/C) was successfully fabricated. Notably, as-obtained MD-PtCo/C (Pt, 0.9532 wt.%) electrocatalyst achieves high utilization rate of ultra-low Pt load and exhibits favorable electrocatalytic performance with lower onset potential, higher EOR activity, less activation energy (E a) value and better stability compared to commercial Pt/C for ethanol oxidation reaction (EOR). Moreover, the consequence of concentrations (KOH, C 2 H 5 OH) and temperatures on electrocatalytic activity of EOR have also been studied. This study would be supportive of developing highly active and low-cost electrocatalysts for other catalytic applications. [ABSTRACT FROM AUTHOR]

Improving the catalytic performance of ethanol electro-oxidation reaction (EOR) is crucial for accelerating the commercialization of direct ethanol fuel cells (DEFCs). In this work, AuPd nanowires (NWs) anchored on the hybrid of layered double hydroxides and carbon black (CB) was prepared by a facile procedure for anode electrocatalyst of ethanol electro-oxidation reaction (EOR). For comparison, unloaded AuPd NWs and AuPd nanopaticles (NPs) supported on LDH-CB were also prepared. These catalysts were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The performance of these catalysts was evaluated by the reactions of ethanol in alkaline media by cyclic voltammetry, chronoamperometric measurements and electrochemical impedance spectroscopy. It was found that the as-prepared AuPd NWs/LDH-CB demonstrated higher activity and stability than those of unloaded AuPd NWs, commercial Pd/C and AuPd NPs/LDH-CB attributed to the AuPd nanowires with more active sites, electronic structure of Pd modified by alloyed with Au and interacted with LDH-CB as well as the electron transfer ability facilitated by CB. Image 1 • Monodispersed LDH sheets were prepared to support AuPd catalyst. • AuPd nanowires anchored on the hybrid of LDH-CB were prepared by a facile strategy. • Strong interactions of electrons promoted the enhancement of catalytic performance. • AuPd NWs/LDH-CB displayed super-higher catalytic performance for EOR. [ABSTRACT FROM AUTHOR]

Abstract Direct ethanol fuel cells are highly promising energy conversion devices, but the complete oxidation of ethanol to CO 2 at low temperatures is still one of the main challenges. Titanium oxycarbide (TiO 1-x C x) powder is investigated as stable and synergistic support for Pt nanoparticles during the ethanol oxidation reaction (EOR) in acidic electrolytes. EOR products are quantitatively detected online with differential electrochemical mass spectrometry. At room temperature, Pt/TiO 1-x C x has a CO 2 efficiency maximum of 8.9%, while only 1.7% are measured for Pt nanoparticles on Vulcan carbon (Pt/C). The reaction pathway is channeled towards the formation of C1 products, while C2 product formation is suppressed. This effect is expected to be much enhanced at elevated temperatures which makes TiO 1-x C x a highly interesting catalyst support material in general. Graphical abstract Image 1 Highlights • The electrocatalytic activity of Pt/TiOC towards the EOR exceeds that of Pt/C. • EOR products are quantitatively detected online with DEMS. • The RT CO 2 efficiency of Pt/TiOC is enhanced and outperforms that of Pt/C. • The C2-pathway is largely suppressed with enhancement of the CO 2 efficiency. • TiO 2 formation enhances the CO tolerance of Pt through a bifunctional mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Direct ethanol fuel cells (DEFCs) have great activity as a green energy conversion device. However, the weak activity of most anode electrocatalysts for the CC bond cleavage is an obstacle to the DEFCs development. Herein, a simple galvanic replacement reaction strategy to synthesize hollow and porous PtRhCu trimetallic nanoboxes (CNBs) with a tunable Pt/Rh atomic ratio is developed. For the ethanol oxidation reaction (EOR), PtRhCu CNBs show morphology and composition‐dependent electrocatalytic activity. The composition optimized Pt54Rh4Cu42 CNBs exhibit excellent specific and mass activity and stability for the EOR, which is attributed to its unique geometric structure and synergistic effects. The hollow porous structure can effectively enhance the atomic utilization and mass transfer. The introduction of Cu improves the antipoisoning capability for CO. The introduction of Rh elevates the self‐stability of PtRhCu CNBs. More importantly, further electrochemical results confirm that the introduction of Rh significantly promotes the cleavage of CC bonds, leading to the transformation of the main catalytic pathway for EOR from C2 to C1 pathway. The real concentration detection for C2 products (CH3COOH and CH3CHO) shows Pt54Rh4Cu42 CNBs have a nearly 11.5‐fold C1 pathway enhancement compared to Pt nanoparticles, showing an obvious selectivity enhancement for the C1 pathway. [ABSTRACT FROM AUTHOR]

Ethanol electrooxidation in acid medium was investigated on Pt-Ru-Sn/C, Pt-Ru/C and Pt-Sn/C. The electrocatalysts were synthesized by microwave assisted chemical reduction reaction. The samples were characterized by transmission electron microscopy (TEM), X-ray diffraction analysis (XRD) and electrochemical analysis for the electrooxidation of ethanol. The ternary electrocatalyst was evaluated in an experimental Direct Ethanol Fuel Cell (DEFC). The method of synthesis used in this work allowed the formation of nanostructured electrocatalysts. The results obtained by electrochemical studies showed that the ternary system Pt-Ru-Sn/C exhibited the highest activity with respect to the binary systems Pt-Ru/C and Pt-Sn/C for carrying out the ethanol electrooxidation reaction. 0.4 mg·cm-2 of electrocatalytic load of Pt-Ru-Sn/C was placed in the anode of an experimental fuel cell operating at room temperature. It was possible to obtain a power density of 0.14, 0.12 and 0.11 mW·cm-2 after 20, 40 and 60 minutes respectively. The experiments were carried out at a controlled temperature of 297 K and they showed the feasibility to produce electricity at room temperature by using this ternary electrocatalyst in Direct Ethanol Fuel Cells. [ABSTRACT FROM AUTHOR]

Direct ethanol fuel cells (DEFCs) are a promising technology for the generation of electricity via the direct conversion of ethanol into CO 2 , showing higher thermodynamic efficiency and volumetric energy density than hydrogen fuel cells. However, implementation of DEFCs is hampered by the low CO 2 selectivity during the ethanol oxidation reaction (EOR). Comprehensive understanding of the electro-kinetics and reaction pathways of CO 2 generation via C C bond-breaking is not only a fundamental question for electro-catalysis, but also a key technological challenge since practical implementation of DEFC technology is contingent on its ability to selectively oxidize ethanol into CO 2 to achieve exceptional energy density through 12-electron transfer reaction. Here, we present comprehensive in situ potentiodynamics studies of CO 2 generation during the EOR on Pt, Pt/SnO 2 and Pt/Rh/SnO 2 catalysts using a house-made electrochemical cell equipped with a CO 2 microelectrode. Highly sensitive CO 2 measurements enable the real time detection of the partial pressure of CO 2 during linear sweep voltammetry measurements, through which electro-kinetics details of CO 2 generation can be obtained. In situ CO 2 measurements provide the mechanistic understanding of potentiodynamics of the EOR, particularly the influence of ∗ OH adsorbates on CO 2 generation rate and selectivity. Density functional theory (DFT) simulations of Pt, Pt/SnO 2 , and Pt/Rh/SnO 2 surfaces clarify reaction details over these catalysts. Our results show that at low potentials, inadequate ∗ OH adsorbates impair the removal of reaction intermediates, and thus Pt/Rh/SnO 2 exhibited the best performance toward CO 2 generation, while at high potentials, Rh sites were overwhelmingly occupied (poisoned) by ∗ OH adsorbates, and thus Pt/SnO 2 exhibited the best performance toward CO 2 generation. [ABSTRACT FROM AUTHOR]

The synergetic effect of alloy and morphology of nanocatalysts play critical roles towards ethanol electrooxidation. In this work, we developed a novel electrocatalyst fabricated by one-pot synthesis of hierarchical flower-like palladium (Pd)-copper (Cu) alloy nanocatalysts supported on reduced graphene oxide (Pd-Cu/RGO) for direct ethanol fuel cells. The structures of the catalysts were characterized by using scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectrometer (XPS). The as-synthesized Pd-Cu/RGO nanocatalyst was found to exhibit higher electrocatalytic performances towards ethanol electrooxidation reaction in alkaline medium in contrast with RGO-supported Pd nanocatalyst and commercial Pd black catalyst in alkaline electrolyte, which could be attributed to the formation of alloy and the morphology of nanoparticles. The high performance of nanocatalyst reveals the great potential of the structure design of the supporting materials for the future fabrication of nanocatalysts. [ABSTRACT FROM AUTHOR]

This paper presents the study of a simple and fast method to prepare an activated hydrothermal carbon supported nickel electrocatalyst (Ni/aHC) for ethanol oxidation reaction (EOR) in alkaline medium. The cyclic voltammogram obtained for the Ni/aHC sample in a 1.0 mol L −1 NaOH solution shows an anodic and a cathodic peak. These redox couple reaction peaks can be related to the reversible formation of (NiO)OH. The catalytic activity of the Ni/aHC sample regarding the EOR is clearly evident from the cyclic voltammogram obtained in presence of ethanol, where a significant increase in the current density from 0.55 V vs . Hg/HgO is observed. This potential value, related with the onset potential (E onset ) of the EOR, is very close to the corresponding (NiO)OH formation potential, confirming that this species is directly involved in the EOR on the Ni/aHC electrocatalyst. The in-situ Attenuated Total Reflectance FTIR ( in-situ ATR-FTIRS) spectra of this sample show two intense peaks related with acetate ion formation. Based on the ATR-FTIRS and electrochemical analyses, and in the literature information, a reaction pathway of the EOR on Ni/aHC in alkaline medium is proposed. [ABSTRACT FROM AUTHOR]

Ni/Graphite electrocatalysts (Ni/G) are successfully prepared through electrodeposition of Ni from acidic (pH = 0.8) and feebly acidic (pH = 5.5) aqueous Ni (II) baths. The efficiencies of such electrodes are investigated as anodes for direct alkaline ethanol fuel cells through their ethanol electrooxidation cyclic voltammetric (CV) response in alkaline medium. A direct proportionality between the amount of the electrodeposited Ni and its CV response is found. The amounts of the deposited Ni from the two baths are recorded using the Electrochemical Quartz Crystal Microbalance (eQCM). The Ni/G electrodes prepared from the feebly acidic bath show a higher electrocatalytic response than those prepared from the acidic bath. Surface morphology of the Ni particles electrodeposited from feebly acidic bath appears in a nano-scale dimension. Various electrochemical experiments are conducted to confirm that the Ni/G ethanol electrooxidation CV response greatly depends on the pH rather than nickel ion concentration of the deposition bath. The eQCM technique is used to detect the crystalline phases of nickel as α-Ni(OH) 2 /γ-NiOOH and β-Ni(OH) 2 /β-NiOOH and their in-situ inter-transformations during the potentiodynamic polarization. [ABSTRACT FROM AUTHOR]

Metal oxides are investigated, as additives of a PtRu/C catalyst, for enhancing the electro-oxidation of ethanol in acidic solution. High surface area TiO 2 and SnO 2 additives are synthesized and physico-chemically characterized. These oxides are added to PtRu/C during the catalytic ink preparation to obtain tri-metallic composite electrodes. These composite electro-catalysts are investigated for the ethanol electro-oxidation in half-cell configuration in comparison with additive-free PtRu/C and Pt/C catalysts. The PtRu-based composite catalyst containing SnO 2 promoter shows a lower onset potential and larger current density for ethanol oxidation than the additive-free catalyst and that containing TiO 2 promoter. The composite catalysts (PtRu/C + metal oxide) are also used in a direct ethanol fuel cell under practical operating conditions and assessed against the benchmark PtRu catalyst. An increase in performance is recorded with the composite tri-metallic electrodes. The analysis of electro-catalytic activity towards ethanol oxidation reaction and ethanolic residues coverage indicates an enhanced capability to activate ethanol chemisorption or a larger electroactive surface area, together with a faster intrinsic activity at lower overpotential, as the reasons for the improved performance with the use of metal oxide additives. [ABSTRACT FROM AUTHOR]

Highly active and stable carbon supported PtSnO 2 catalyst with Pt:Sn ratio of 3:1 is prepared by a modified polyol method. The tin oxide is prepared via a facile co-precipitation method using stannic chloride solution and calcined at 500 °C to form only tetragonal rutile structures of SnO 2 . The PtSnO 2 /C catalyst is synthesized through an ex situ method named as PtSnO 2 /C (E). The role of SnO 2 and preparation method of PtSnO 2 (E) to enhance the ECSA, for oxidation of ethanol, are considered and the activity is compared to synthesized in situ catalyst named PtSnO 2 (I) method using SnCl 2 . The electro-catalysts are characterized using XRD, SEM-EDX, ICP-OES, TEM, Cyclic Voltammetry (CV), Choronoamperometry (CA), Electrochemical Impedance Spectroscopy (EIS) and direct alcohol fuel cell test (DAFC). The ethanol and acetaldehyde oxidation reaction activity of the catalyst are compared to PtSnO 2 /C (I) and Pt/C and ranked in order: PtSnO 2 (E) > PtSnO 2 (I) > Pt. It is found that the stability of PtSnO 2 /C (E) is considerably higher than that of PtSnO 2 /C (I) and Pt/C. The direct ethanol fuel cells (DEFCs) with PtSnO 2 /C (E) and PtSnO 2 /C (I) as modified electro-catalyst and Pt/C anode catalyst are also tested with ethanol and filled with acetaldehyde as a fuel. The synthesized catalyst shows higher open circuit voltage (OCV) and power density for ethanol and acetaldehyde compared with PtSnO 2 /C (I) and Pt/C as anode catalysts. [ABSTRACT FROM AUTHOR]

Even though platinum is known as an active electro-catalyst for ethanol oxidation at low temperatures (< 100 °C), choosing the electrode material for ethanol electro-oxidation is a crucial issue. It is due to its property which easily poisoned by a strong adsorbed species such as CO. PtSn-based electro-catalysts have been identified as better catalysts for ethanol electro-oxidation. The third material is supposed to improve binary catalysts performance. This work presents a study of the ethanol electro-oxidation on carbon supported Pt-Sn and Pt-Sn-Ni catalysts. These catalysts were prepared by alcohol reduction. Nano-particles with diameters between 2.5-5.0 nm were obtained. The peak of (220) crystalline face centred cubic (fcc) Pt phase for PtSn and PtSnNi alloys was repositioned due to the presence of Sn and/or Ni in the alloy. Furthermore, the modification of Pt with Sn and SnNi improved ethanol and CO electro-oxidation. [ABSTRACT FROM AUTHOR]

The electrocatalytic activity of Pt/C, Pt-Rh/C and Pt-Rh-SnO2/C electrocatalysts toward the ethanol oxidation reaction (EOR) was investigated in a three-electrode assembly at 25 °C, 40 °C and 70 °C in acidic medium. The 10 wt.% electrocatalysts were prepared with a modified polyol method and physically characterized by both X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The CO-stripping study revealed that COad oxidation initiates at lower potential on Pt-Rh/C and Pt-Rh-SnO2/C than on Pt/C and shifts negatively when the temperature increases. The positive effect of the temperature is maintained for the EOR: the three electrocatalysts exhibit a higher activity and a negative shift of the EOR wave at higher temperature. Pt-Rh-SnO2/C demonstrates the lowest EOR onset potential of the three electrocatalysts. The steady-state Tafel slopes and apparent activation energies Ea were determined in 0.5 M H2SO4 + 0.1 M EtOH between E = 0.4 and 0.7 V vs. RHE in the temperature range 25-70 °C. The results show rather comparable rate determining steps ( rds) for the ethanol electrooxidation on Pt/C and Pt-Rh/C in the ranges of potential and temperature studied. The EOR on Pt-Rh-SnO2/C seems less influenced by the potential than on Pt/C and Pt-Rh/C electrocatalysts, but is more temperature sensitive. [ABSTRACT FROM AUTHOR]

Direct ethanol fuel cells are based in ethanol electro-oxidation at low temperature and they constitute an alternative energy conversion system. However, they need catalysts in order to improve their efficiency, given that ethanol electro-oxidation is a slow-kinetic reaction. Among those catalysts platinum and platinum alloys play an important role in the increase of the ethanol cleavage kinetics for fuel cell application. However, to maximize the catalyst performance, support materials are needed in order to reduce the catalyst load considering its high cost. One of the more versatile catalyst supports is activated carbon. Recently, attention has focused on wood as carbon material precursor, because of its sustainability and also because the obtained carbons have excellent final properties. In the present work, activated carbon obtained by physical activation of Eucalyptus grandis wood (biocarbon) was tested as Pt and PtSn catalyst support, for ethanol electro-oxidation reaction. For comparison purposes, commercial activated carbon Vulcan XC72 was also tested. The catalyst supports were characterized by textural analysis, elemental analysis and infrared spectroscopy. The obtained catalysts were characterized regarding structure by XRD and their electrochemical behavior was evaluated by cyclic voltammetry. Biocarbon-supported PtSn electrocatalysts showed better electrochemical performance related to the commercial activated carbon (Vulcan XC72)-supported ones, since its developed current density and potential were the highest and its onset potential was the lowest. However, pure platinum showed better values for current density, potential and onset potential in Vulcan XC72-based activated carbons, being the untreated one the best support in this case. [ABSTRACT FROM AUTHOR]

Abstract: The electro-oxidation of ethanol by the catalyst of PtRu nanoparticles supported on a TiO2-embedded carbon nanofiber (PtRu/TECNF), which has recently been proposed by the authors as a highly active catalyst for methanol oxidation, is investigated by cyclic voltammetry using a glassy carbon electrode and by operating a direct ethanol fuel cell (DEFC) with the catalyst. The mass activity obtained from the cyclic voltammogram for the ethanol oxidation is compared to that for the methanol oxidation reported in our recent paper. The mass activity for the ethanol oxidation is comparable or slightly higher than that for the methanol oxidation, and the relationship between the TECNF composition, i.e., the Ti/C mass ratio, and the activity are also similar to that for the methanol oxidation. A DEFC fabricated with the PtRu/TECNF shows a higher power output compared to that with the commercial PtRu/C catalyst. An analysis of the reaction products by a simple two-step reaction model reveals that the PtRu/TECNF increases the rate constant for the reaction steps from ethanol to acetaldehyde and subsequently to CO2, but decreases that from acetaldehyde to acetic acid. This means that the PtRu/TECNF improves not only the kinetics, but also the selectivity to acetaldehyde. [Copyright &y& Elsevier]

The sluggish kinetics of ethanol oxidation on Pt-based electrodes is one of the major drawbacks to its use as a liquid fuel in direct ethanol fuel cells, and considerable efforts have been made to improve the reaction kinetics. Herein, we report an investigation on the effect of the Pt microstructure (well-dispersed versus agglomerated nanoparticles) and the catalyst support (carbon Vulcan, SnO, and RuO) on the rate of the electrochemical oxidation of ethanol and its major adsorbed intermediate, namely, carbon monoxide. By using several structural characterization techniques such as X-ray diffraction, X-ray absorption spectroscopy, and transmission electron microscopy, along with potentiodynamic and potentiostatic electrochemical experiments, we show that by altering both the Pt microstructure and the support, the rate of the electrochemical oxidation of ethanol can be improved up to a factor of 12 times compared to well-dispersed carbon-supported Pt nanoparticles. As a result of a combined effect, the interaction of Pt agglomerates with SnO yielded the highest current densities among all materials studied. The differences in the activity are discussed in terms of structural and electronic properties as well as by mass transport effects, providing valuable insights to the development of more active materials. [ABSTRACT FROM AUTHOR]

Abstract: A Ni nanowire array (NiNWA) supported three-dimensional flower-like Pd nano-electrocatalyst with high electrocatalytic performance for the electrooxidation of ethanol in alkaline media has been fabricated by borohydride hydrothermal reduction method. This novel hybrid NiNWA/PdNF (nanoflowers) electrocatalyst exhibits large electrochemically active surface area (EASA, 45m2 g−1(Pd)), excellent electrocatalytic activity (765mAmg−1(Pd)), and high level of the poisoning tolerance (I f /I b =1.2) to the carbonaceous oxidative intermediates for the electrooxidation reaction in alkaline media. In addition, the electrochemical stability of NiNWA/PdNF is significantly higher than that of NiNWA/PdNP (nanoparticles) electrocatalyst, as evidenced by chronoamperometry experiments in which the electrooxidation current of nanoflowers is controlled by the diffusion transport of ethanol species rather than the carbonaceous poisoning. This high electrocatalytic activity can be attributed to the more open structure with higher electrochemically active sites and shape of Pd nanoflowers. This is further enhanced by the core support NiNWA with a very large surface area and the open interspaces that ensure easy alcohol access even to remote active sites for fast ion adsorption/desorption. [Copyright &y& Elsevier]

Abstract: Carbon supported Pt–Sn catalysts were prepared by reduction of Pt and Sn precursors with formic acid and characterized in terms of structure, morphology and surface properties. The electrocatalytic activity for ethanol oxidation was studied in a direct ethanol fuel cell (DEFC) at 70°C and 90°C. Electrochemical and physico-chemical data indicated that a proper balance of Pt and Sn species in the near surface region was necessary to maximize the reaction rate. The best atomic surface composition, in terms of electrochemical performance, was Pt:Sn 65:35 corresponding to a bulk composition 75:25 namely Pt3Sn1/C. The reaction products of ethanol electro-oxidation in single cell and their distribution as a function of the nature of catalyst were determined. Essentially, acetaldehyde and acetic acid were detected as the main reaction products; whereas, a lower content of CO2 was formed. The selectivity toward acetic acid vs. acetaldehyde increased with the increase of the Sn content and decreased by decreasing the concentration of the reducing agent used in the catalyst preparation. According to the recent literature, these results have been interpreted on the basis of ethanol adsorption characteristics and ligand effects occurring for Sn-rich electrocatalysts. [Copyright &y& Elsevier]

Abstract: In the present work, the activity of Pt x Sn y /C catalysts towards ethanol, acetaldehyde and acetic acid electrooxidation reactions is investigated for each one separately by means of cyclic voltammetry. To this purpose, a series of Pt x Sn y /C catalysts with different atomic ratio (x:y =2:1, 3:2, 1:1) and small particle size (∼3nm) are fast synthesized by using the pulse microwave assisted polyol method. The catalysts are well dispersed over the carbon support based on the physicochemical characterization by means of XRD and TEM. Concerning the ethanol electrooxidation, it is found that the Sn addition strongly enhances Pt''s electrocatalytic activity and the contributing effect of Sn depends on: (i) the Sn content and (ii) the operating temperature. More precisely, at lower temperatures, Sn-rich catalysts exhibit better ethanol electrooxidation performance while at higher temperatures Sn-poor catalysts give better performance. In the case of acetaldehyde electrooxidation, Pt1Sn1/C catalyst exhibits the highest activity at all the investigated temperatures; due to the role of Sn, which could effectively remove C2 species and inhibit the poison formation by supplying oxygen-containing species. Finally, it is found that the Pt x Sn y /C catalysts are almost inactive (little current was measured) towards the acetic acid electrooxidation. The above findings indicate that Sn cannot substantially promote the electrooxidation of acetic acid to C1 species. [Copyright &y& Elsevier]

Abstract: Pt2Sn1 nanoparticles supported on wormholelike mesoporous carbons (WMCs) with three different pore diameters, namely WMC-F7, WMC-F30, and WMC-F0 have been synthesized by adopting a modified pulse microwave-assisted polyol method. The pore diameters (Dp) of WMC-F7, WMC-F30, and WMC-F0 are 8.5 nm, 4.4 nm, and 3.1 nm respectively, while the particle size of Pt2Sn1 (DPt) on each support is identical (∼3 nm). Based on the experimental results, it has been found that the pore diameter plays an important role in the electrochemical activity of Pt2Sn1 catalysts towards ethanol electrooxidation reaction (EOR). Pt2Sn1/WMC-F7 catalyst exhibits the highest electrochemical surface area (ESA) and activity towards EOR. Moreover, Pt2Sn1/WMC-F7 gives the comparable activity to the Pt2Sn1 supported on the commercial XC-72 carbon. However, in the cases of WMC-F30 (DPt < Dp < 2 DPt) and WMC-F0 (Dp = DPt) as the supports, the corresponding catalysts obtain much lower ESA and EOR activity with respect to WMC-F7 (Dp > 2 DPt). This could be attributed to the easy accessibility of Pt2Sn1 nanoparticles in the case of WMC-F7 with Dp > 2 DPt for the easy fuel transportation, and consequently the EOR activity has been greatly improved. [Copyright &y& Elsevier]

Abstract: To find a more durable anode with high performance for direct ethanol fuel cells (DEFCs), the present study investigates a series of quaternary electrocatalysts, Pt30Ru30Ir40−x Sn x /C (wt.%), for the ethanol electro-oxidation reaction (EOR). The carbon-supported Pt30Ru30Ir40−x Sn x /C electrocatalysts were prepared by a known impregnation-reduction (borohydride) method. The microstructure and chemical composition were determined by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The activity of the electrocatalysts for EOR was compared to commercial Pt67Ru33/C (HISPEC5000) using linear sweep voltammetry (LSV) based on similar Pt loading. The results of this study show that electrocatalyst composition with 10 and 20% Ir (wt.%) exhibit higher electrocatalytic activity than the commercial PtRu electrocatalyst. The single fuel cell testing at 90°C comparing Pt30Ru30Ir40−x Sn x /C to commercial Pt67Ru33/C and Pt83Sn17/C anodes showed an enhancement of Pt activity (normalized to Pt loading) in the following order: Pt30Ru30Ir10Sn30 >Pt30Ru30Sn40 ≥Pt30Ru30Ir40 ≥Pt83Sn17 >Pt67Ru33. After a long-term performance test, the activity changed to the following order: Pt30Ru30Ir10Sn30 >Pt30Ru30Ir40 >Pt30Ru30Sn40 >Pt83Sn17 >Pt67Ru33. Pt30Ru30Ir10Sn30/C exhibited both a higher performance with a specific power density of 29mWmgPt −1 without O2 backpressure at the cathode and an excellent long-term stability in a DEFC operating at 90°C. [Copyright &y& Elsevier]

Nanocrystalline Pd electrocatalyst promoted with transition metal oxide (Co3O4, NiO, and CoNiOx) is successfully synthesized on high surface carbon support by using intermittent microwave heating (IMH) method. The physical properties of the catalysts are characterized by XRD, TEM, and EDX. The results show that there is no significant microstructure change between Pd and Pd-oxide electrocatalysts and the particle sizes are in the range 5.8–3.9 nm. The linear sweep voltammogram and chronoamperometry results for the electro-oxidation of ethanol show that Pd-oxide/C electrocatalysts exhibit much better electrochemical activity and stability as compared with pure Pd/C electrocatalyst. The results show that Pd–CoNiOx/C exhibits the best stability and highest electro-oxidation activity, indicating the promising potential as an alternative electrocatalysts for the direct ethanol fuel cells. [ABSTRACT FROM AUTHOR]

Abstract: By comparing the performance of fuel cells operating on some low molecular weight alcohols, it resulted that ethanol may replace methanol in a direct alcohol fuel cell. To improve the performance of a direct ethanol fuel cell (DEFC), it is of great importance to develop anode catalysts for ethanol electro-oxidation more active than platinum alone. This paper presents an overview of catalysts tested as anode and cathode materials for DEFCs, with particular attention on the relationship between the chemical and physical characteristics of the catalysts (catalyst composition, degree of alloying, and presence of oxides) and their activity for the ethanol oxidation reaction. [Copyright &y& Elsevier]

Abstract: Pt-CeO2/C and a series of Pt-Ce x Zr1−x O2/C catalyst powders with different Ce/Zr ratio were prepared and evaluated in terms of the electrochemical activity for ethanol electro-oxidation using cyclic voltammetry (CV), steady state polarization experiments and CO-stripping technique at room temperature. XRD results show that Ce x Zr1−x O2 and Pt coexist in the Pt-Ce x Zr1−x O2/C catalyst and Ce x Zr1−x O2 has no effect on the crystalline lattice of Pt. TEM results show that the Pt and Ce x Zr1−x O2 particles dispersed uniformly over the surface of the carbon black. Cyclic voltammetry results show that the mass activity and specific activity of Pt-CeO2/C for ethanol electro-oxidation is higher than that of Pt/C. The structure and Ce/Zr ratio of Pt-Ce x Zr1−x O2/C has effect on the catalytic activity of catalysts. CO-stripping voltammetry showed that the inclusion of CeO2 and Ce x Zr1−x O2 favors the CO oxidation at lower potential. [Copyright &y& Elsevier]

Abstract: This work reports some advances in the development of catalysts for ethanol electro-oxidation. A sol–gel-based method was used to incorporate different metal oxides on a substrate composed of platinum dispersed on carbon (Pt/C), resulting in very active catalysts with high surface area. Ruthenium and iridium oxides were used as modifiers, either alone or combined, maintaining a proportion of 25% in their total mass, as related to the amount of platinum on the substrate. The catalyst behavior was evaluated by polarization curves and the results were compared with commercially available catalysts. The experimental data reveals a superior performance of the sol–gel-based materials, indicating that the proposed method is a promising alternative to prepare catalysts to be used in the direct electrochemical oxidation of ethanol. [Copyright &y& Elsevier]

Abstract: In this paper, Pt–ZrO2/C catalysts were prepared and compared with Pt/C(20wt% E-TEK)in terms of the electrochemical activity for ethanol oxidation using cyclic voltammetry (CV), Tafel plot and electrochemical impedance spectroscopy in alkaline solutions. All the results showed that Pt–ZrO2/C gave higher catalytic activity for ethanol electro-oxidation. The effect of Pt:ZrO2 molar ratio on the catalytic activity was also investigated by CV and the lowest peak potential for ethanol electro-oxidation appeared at the molar ratio of 1:4. [Copyright &y& Elsevier]

[Display omitted] • Pd/C electrocatalysts are used for amperometric sensors and also for Fuel Cells. • Size-induced effects on Pd/C resulted in distinct tendency to interact with oxygen. • Electrocatalytic activity towards ethanol oxidation depends on the surface oxophilicity. • PdO acts both as a promoter and/or inhibitor towards ethanol oxidation. • The catalytic activity can be enhanced by 57% only by varying surface oxophilicity. The ability of a surface to interact with oxygen (oxophilicity) plays a very important role in several catalytic, electroanalytic and electrocatalytic reactions. To date, however, the role of the oxophilicity in the electrochemical oxidation of ethanol was never shown for pure nanostructured Pd electrocatalysts supported on carbon, a promising material to be used as a non-enzymatic amperometric sensors for ethanol and also as an electrocatalyst for the Direct Ethanol Fuel Cells. In this work, Pd nanoparticles were prepared by chemical reduction at room temperature in the presence of varying amounts of sodium citrate in order to produce particles with distinct sizes. Then, we used cyclic voltammetry in 0.1 mol L-1 KOH to obtain an oxophilicity trend among various nanostructured Pd/C samples. The oxidation of ethanol in alkaline media demonstrated that the surface oxophilicity has a dual role in the kinetics of the reaction: a promoter at low and medium oxygen coverages, and a spectator (inhibitor) species at high surface coverages. Thus, by a proper control of the surface oxophilicity the current density at a constant potential can be enhanced by 57%, highlighting the importance of that parameter in the electro-oxidation on ethanol on Pd-based materials. Our results have a great impact for the design of more active non-enzymatic ethanol sensors and also for the development of more active electrocatalysts for Direct Ethanol Fuel Cells. [ABSTRACT FROM AUTHOR]

One of the most challenges in Direct Ethanol Fuel Cell (DEFC) is to prevent the poisoning of the surface of the electrode due to the slow kinetics of ethanol oxidation reaction. Herein, we report the development of a new catalysts for ethanol oxidation using a well-defined Cu 2 O nanodendrites (Cu 2 O-NDs) supported on polypyrrole film (PPy) using a simple electrochemical approach. The effect of regeneration of the electrocatalyst in acidic medium on the performance of ethanol electro-oxidation was reported for the first time. Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) were used to characterize the new catalysts. The SEM and TEM images confirm that the octahedral shape of Copper oxide is converted to a dendritic one after the regeneration of the catalyst. The electrochemical behavior of the prepared catalysts towards the oxidation of ethanol were investigated by Cyclic voltammetry (CV), Chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The current obtained by CV measurements on Cu 2 O-NDs/PPy/CPE was about 4 mA cm−2 which is 1.77 time higher than Cu 2 O/PPy/CPE catalyst (2.25 mA cm−2) with a shift of 60 mV and 150 mV in anodic and onset potential respectively demonstrating a good catalytic performance for ethanol oxidation. The stability test shows that the Cu 2 O-NDs/PPy/CPE loses only 7.25% of its initial current after 1000 cycles. Finally, Ex–situ FTIR spectroscopy was conducted in order to understand the reaction mechanism. Interestingly, our ex-situ FTIR results demonstrated that the ethanol oxidation mechanism displayed shape dependent behavior of copper oxide, indicating that the ethanol molecules are totally oxidized on the Cu 2 O-NDs leading to the formation of CO 2 molecule as final product. [Display omitted] • Cu 2 O-NDs/PPy catalyst was synthesized by a simple electrochemical method. • The regeneration of Cu 2 O influences their catalytic performances towards EOR. • Cu 2 O-NDs/PPy displayed a higher catalytic activity towards EOR. • Cu 2 O-NDs/PPy is more efficient in breaking the C C bond than Cu 2 O/PPy. [ABSTRACT FROM AUTHOR]

The design of highly efficient and stable non-noble transition metal-based electrocatalysts for the ethanol oxidation reaction (EOR) is imperative for the development of the direct ethanol fuel cells (DEFCs). In this work, we report a simple template-free method for preparing a type of rod-like Cu–Ni alloy particle with the unique porous structure and evaluate it as the electrocatalyst for the EOR in alkaline media. The pH, which was adjusted by the addition of NH 3 ·H 2 O during the liquid-phase coprecipitation process, was found to be a key factor to shape Cu–Ni alloy precursor into a quasi-one-dimensional morphology. After annealing at a reducing atmosphere (H 2 /Ar = 5/95, v/v), well-alloyed Cu–Ni rods with the predefined molar ratio (Cu/Ni) of 1:1, a specific surface area of 6.84 m2 g−1, and the average pore size of 30.97 nm were obtained. Cyclic voltammetry (CV) and chronoamperometry (CA) test results show that the prepared Cu–Ni alloy catalyst demonstrated an anodic current peak of 86.10 mA cm−2 in the presence of 0.2 M ethanol and a 95% retention of current density after 2000 s, indicating its good electrochemical performance in terms of catalytical activity and long-term stability. This bottom-up synthesis strategy would enrich the fabrication methodologies and open up a promising avenue for preparing multiple Ni-based EOR electrocatalysts with the easy-controllable morphologies and porous structure at the industrial scale. Image 1 • Novel Cu–Ni alloy rods were prepared via a facile template-free method coupled with the thermal annealing treatment. • NH 3 -induced oriented growth mechanism of Cu–Ni alloy precursor was proposed. • The molar ratio of Cu and Ni can be accurately controlled and the hierarchical porous structure is obtained. • The binary alloy shows the enhanced EOR catalytical performance compared to pure Ni. [ABSTRACT FROM AUTHOR]

• Ethanol electro-oxidation mechanisms were investigated by ab initio molecular dynamics on solvated Pt(1 0 0). • Whole catalytic cycle from ethanol to acetic acid and CO 2 was revealed at free energy landscape. • Ethanol decomposition rates are sufficiently high. • Slow oxidation kinetics of surface intermediates into final products is the main obstacle. • Weakening the surface reactivity towards intermediates adsorption was suggested to improve the catalytic activity. The use of ethanol fuel in direct ethanol fuel cells has been hindered by the slow kinetics of anodic ethanol electro-oxidation reactions over Pt catalysts. We employ ab initio molecular dynamics simulations and thermodynamic integrations on the solvated Pt(1 0 0) model electrode surface with explicit water molecules, to systematically investigate the ethanol electrocatalytic oxidation mechanisms including partial oxidation to acetic acid and complete oxidation to CO 2. We find that the ethanol decomposition rate does not limit the overall efficiency of the ethanol electro-oxidation reaction. However, the slow oxidation kinetics of surface intermediates to final products, due to the bonding between intermediates and the Pt surface being too strong, is the main obstacle. We suggest that weakening the surface affinity towards adsorption of the intermediates such as CO, for example by engineering the surface structures (e.g. via alloying), could improve the overall catalytic effeciency for ethanol electro-oxidation reaction. [ABSTRACT FROM AUTHOR]

• PtPd PNCs were prepared via synthesis of AgPtPd NDs followed by selective etching.. • PtPd PNCs exhibited high surface area and high porosity compared to counterparts. • The mass activity and durability of PtPd PNCs are superior compared to counterparts. Direct ethanol fuel cells (DEFCs) have received great interest owing to their high power density and environmental friendness. Nevertheless, the designing of active, durable, and efficient anode for DEFCs is a profound challenge. In this context, we reported the synthesis of PtPd porous nanoclusters (PtPd PNCs) as electrocatalyst for ethanol oxidation reaction (EOR). This was implemented through two-step synthesis. Firstly, ternary AgPtPd nanodendrites (NDs) were synthesized via ultrasound-assisted co-reduction of the metal precursors using ascorbic acid (AA) as a mild reductant and Pluronic F127 as structure-directing agent. Thereafter, PtPd PNCs were created by selective chemical etching of AgPtPd nanocrystals in 1 M HNO 3. The textural properties, morphology, and elemental composition of the studied electrocatalysts were investigated, and their catalytic activities towards ethanol electrooxidation were examined. PtPd PNCs revealed a high surface area of 83.0 m2 g−1 and high porosity compared to its counterparts. Additionally, it depicted enhanced catalytic performance towards ethanol electrooxidation in 1 M KOH with mass activity of 1.8 A mg−1 compared to PtPd NDs (0.97 A mg−1), Pt NDs (0.51 A mg−1), and Pt/C (0.33 A mg−1). The enhanced catalytic performance of PtPd PNCs was ascribed to high surface area, high porosity, and increased active sites. [ABSTRACT FROM AUTHOR]

• The Pt/Rh(1 1 1) interface could convert ethanol to form CH 3 CO*. • Oxygen-containing species adlayers are formed on Rh(1 1 1) at low potentials (<0.5 V). • OH* could couple with CH 3 CO* at the interface to produce CH 3 COOH. • (1 1 1) × (1 1 0) interface is more active for ethanol electro-oxidation. Finding a highly efficient electro-catalyst for ethanol oxidation is the central issue in the use of direct ethanol fuel cells. Recently, fabricating interfacial sites between two phases has been reported as an effective approach to boost the heterogeneous catalytic activity. In this work, a comprehensive understanding of how the Pt/Rh(1 1 1) interface promotes ethanol electro-oxidation for direct ethanol fuel cells at atomic levels is gained by employing density functional theory (DFT) calculations. It is found that the Pt/Rh(1 1 1) interface including (1 1 1) × (1 1 0) and (1 1 1) × (1 0 0) could effectively convert ethanol to CH 3 CO* and the Rh(1 1 1) surface could activate water at low potentials (<0.5 V) by forming several ordered surface oxygen-containing species adlayers. Moreover, OH* is identified to be an oxidant and CH 3 CO* oxidation rate on (1 1 1) × (1 1 0) is faster than that on (1 1 1) × (1 0 0). It is therefore suggested that the (1 1 1) × (1 1 0) interface over Pt/Rh(1 1 1) is the active site for catalyzing ethanol electro-oxidation into CH 3 COOH. These results highlight the significance of metal/metal interfaces and help screen such interfacial catalysts in the design of highly active catalysts for ethanol electro-oxidation reactions. [ABSTRACT FROM AUTHOR]

Hereby we present a novel experimental set-up for on-line detection of volatile products formed in a low-temperature fuel cell. The developed set-up, consisting of mass spectrometer and NDIR CO 2 -sensor, was applied to analysis of anode product distribution of a DEFC equipped with model ethanol electro-oxidation catalysts (Pt/C and PtRu/C). The methodology used by us allowed for an on-line detection of electrochemical products of ethanol oxidation with exclusion of products of ethanol oxidation occurring without electron flow in the external circuit (as a result of currentless oxidation by oxygen permeating from the cathode). For instance, it allowed us to observe a distinct time-dependency of CO 2 amounts (as well as for current density) in constant voltage experiments for high- and low cell voltage when Pt/C anode catalyst was used, which was not observed for PtRu/C. We proposed a probable explanation based on dependency of ethanol permeation rate on cell parameters. Gas chromatography was used as a supplementary technique for acetic acid detection (a non-volatile product of ethanol oxidation) and allowed us, in connection with MS and CO 2 -sensor results, to assess the selectivity of the catalysts used at different cell conditions (voltage, temperature etc.). In order to better understand the oxygen crossover phenomenon and its possible effect on the determined amounts of all three main products of ethanol oxidation (acetaldehyde, acetic acid and CO 2), a correction for amounts formed at the open circuit voltage was performed. As the CO 2 was observed in the anode stream in currentless condition, we assumed that it originates from chemical oxidation of ethanol and/or CO adsorbed on the surface of the anode catalyst, by oxygen permeating from cathode. Based on our results, and the literature data for H 2 /O 2 fuel cell fed with H 2 /CO mixture, to the anode, we concluded that oxygen permeation can be beneficial for a working ethanol fuel cell, as it allows for anode depoisoning. Image 1 [ABSTRACT FROM AUTHOR]