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Microfluidic direct ethanol fuel cells are a promising technology for powering electronic portable devices in the future, and the use of efficient electrocatalysts, both anodic and cathodic are crucial for the development of this type of fuel cells. In this work, an Ag-Pt ethanol-tolerant cathode, synthesized by pulsed laser deposition is studied in the presence of high concentration of ethanol. The cathode exhibited similar catalytic activity to Pt towards the oxygen reduction reaction, performing the reaction through a 4 e− pathway but it showed practically no activity towards the ethanol oxidation reaction. Furthermore, the cathode was successfully tested in a microfluidic direct ethanol fuel cell under mixed-reactant conditions, delivering a maximum cell voltage of 0.75 V and maximum power density of 10 mW cm−2, thus demonstrating its capability to selectively accomplish the oxygen reduction reaction in presence of ethanol concentration as high as 2 M. Image 1 • The Pt/Ag catalyst shows activity towards ORR and no activity towards EOR. • The cathode was used in a membraneless microfluidic mixed-reactant fuel cell. • The ethanol crossover effect is negligible. • Higher power density was obtained with respect to a 2-stream ethanol fuel cell. [ABSTRACT FROM AUTHOR]

Developing highly active and stable ethanol oxidation electrocatalysts is crucial for direct ethanol fuel cells. Herein, platinum/molybdenum disulfide nanoflower (Pt/MoS 2) nanocomposite is synthesized through a facile method and is first applied as catalyst for ethanol oxidation reaction. In situ electrochemical nuclear magnetic resonance is carried out to investigate the electrocatalytic activity of Pt/MoS 2 and the detailed mechanism of ethanol oxidation reaction. Experimental results indicate that in situ electrochemical nuclear magnetic resonance possesses great advantages for real-time investigation of ethanol oxidation reaction, and Pt/MoS 2 is found to exhibit better electrocatalytic performances in terms of higher current density, better stability, and stronger anti-poisoning activity compared to commercial Pt/C and pure Pt catalysts in acid electrolyte, suggesting its potential for application in direct ethanol fuel cells. Density functional theory calculations indicate that MoS 2 -supported Pt atom has a smaller energy barrier for the dissociation of ethanol compared to those of Pt and C-supported Pt atom, leading to the enhancement of catalytic activity. This work reveals the importance of the supporting materials for high performance direct ethanol fuel cells catalysts. Image 1 • Pt/MoS 2 is prepared and used as the catalyst for EOR. • Pt/MoS 2 exhibits excellent catalytic performance for EOR. • The intermediate species are identified by in situ EC-NMR. • Pt/MoS 2 has lower energy barrier for dissociation of ethanol than Pt/C. [ABSTRACT FROM AUTHOR]

The article presents modified Pd-based catalysts supported on reduced graphene oxide (rGO), used in the electrooxidation reaction of ethanol in alkaline medium. When NaBH4 reducing agent was used, the random presence of Na was found out. According to this result, Na was used as a promoter of Pd-based catalyst. Consequently, the Al-Si-Na addition not only assisted active phase Pd nanoparticles to disperse homogenously on graphene surport, but also contributed to increase catalytic activity in the reaction. This value, 16138 mA·mg−1Pd, is about 1.5 times higer than that of the catalyst modified by Al-Si. Moreover, the stability of the catalyst is enhanced more. The electrochemical stability of PASGN.N catalyst was relatively good: after 500 scanning cycles, the current density diminished 32% compared with the highest peak current density of the 15th cycle, which was chosen as a reference. These significant improvement results in electrooxidation of ethanol have opened up the high potential application of these catalysts in direct-ethanol fuel cell. [ABSTRACT FROM AUTHOR]

The electrocatalysts with superior activity and stability for ethanol oxidation reaction (EOR) are of critical importance for the development of direct ethanol fuel cells (DEFCs). Herein, an effective multistep wet-chemical method has been developed to controllably synthesize hollow echinus-like shaped Pd-based trimetallic nanospheres (Au@PdAgNSs) and corresponding reduced graphene oxide supported Au@PdAgNSs nanocomposite (Au@PdAgNSs/rGO). The results of various physical characterizations indicate that the as-prepared Au@PdAgNSs is a porous and hollow echinus-shaped core-shell structure with gold as the core and PdAg alloy as the shell. Through the CA and CV measurements the resultant Au@PdAgNSs/rGO demonstrated excellent electrocatalytic activity and stability towards ethanol oxidation in an alkaline medium as compared to a commercial Pd/C catalyst, making it very attractive for application in alkaline DEFCs. Image 1 • Hollow echinus-like Au@PdAgNSs decorated reduced graphene oxide using multistep wet-chemical method were prepared. • Au@PdAgNSs/rGO exhibited superior performance for ethanol electro-oxidation in alkaline media. • The excellent performance of Au@PdAgNSs/rGO derived from unique morphology and combination with rGO. [ABSTRACT FROM AUTHOR]

Summary: A transient, two‐dimensional, and two‐phase model was developed for predicting cell potential decay behavior of direct ethanol fuel cells operated galvanostatically after applying a step change in cell current density. To predict dynamic changes in anode overpotential and product distributions, a multi‐step reaction mechanism based on literatures involving many adsorbed intermediates (CH3CH2OH, CH3CHO, CH3CO, OH) was incorporated into this model. The kinetic rates of reactions involving electron transfers are described by the Butler‐Volmer equation. The surface coverage balance was used to determine the fractional coverage for each adsorbed species. The model also accounts for ethanol crossover through the membrane to cause cathode mixed potential. From the simulation results, a gradual increase of anode overpotential was caused by the acetyl bottleneck effect, leading to a slow decay of cell potential with time. Based on one set of model parameters, the model could accurately predict the dynamic response of cell voltage behavior after the cell current densities were stepped up as well as product selectivity. [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]

At present, ethanol electrooxidation study is performed on CNT supported Pd and PdAu catalysts to investigate the effect of Au addition to Pd towards the ethanol electrooxidation activity. NaBH 4 reduction method is employed for the synthesis of Pd/CNT, Pd 90 Au 10 /CNT, Pd 90 Au 10 /CNT, Pd 70 Au 30 /CNT, Pd 50 Au 50 /CNT, and Pd 40 Au 60 /CNT catalysts. These catalysts are characterized via advanced surface analytical techniques namely N 2 adsortion-desoprtion measurements,X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM). The characterization results revealed that Pd 90 Au 10 /CNT has 205.42 m2/g and 1.18 cm3/g BET surface area (m2/g) and pore volume (cm3/g), respectively. On the other hand, XRD and XPS results revealed that the electronic state of Pd 90 Au 10 /CNT catalyst changed by Au addition to Pd. TEM and HRTEM and elemental mapping results reveal that Pd and Au is homogeneously dispersed and alloying of Pd and Au is clearly observed, in agreement with the XRD and XPS results. Ethanol electrooxidation measurements in alkaline environment are performed by Cyclic Voltammetry (CV), Chronoamperometry (CA), Electrochemical impedance spectroscop (EIS) techniques. Pd 90 Au 10 /CNT displayed the highest specific and mass activity. The synergistic effect between Pd and Au at optimized metal ratio was utilized to obtain an improvement in specific activity. Furthermore, Pd 90 Au 10 /CNT showed the lowest charge transfer resistance (R ct) and a long term stability. As a result, it is clear that PdAu catalyst is a promising catalyst for Alkaline Direct Ethanol Fuel Cells. Image 1 • Carbon nanotube supported Pd and PdAu catalysts were successfully synthesized by NaBH 4 reduction method. • Au improves ethanol electrooxidation activity of Pd in alkaline media. • Pd 90 Au 10 /CNT catalyst is a promising anode catalyst for Alkaline Direct Ethanol Fuel Cells. [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]

Nano-structured PtCo catalysts and their single metal counterparts were chemically synthesized under ethylene glycol (EG), sodium borohydride (BH) and hydrazine (Hz) reduction scheme. EG reduction was found to be the most effective method for fabricating binary PtCo electro-catalysts that are functionally competent for ethanol oxidation reaction (EOR) in alkaline medium due to enrichment of the electronic properties of the combined matrix through individual contribution of the ad atoms and their oxides. The catalyst matrices were subjected to structural morphology and compositional analysis by the respective techniques like EDX, XRD, TEM and BET isotherm. Performance screening of the entire set of catalysts at room temperature was carried out employing a series of electrochemical techniques involving voltammetry, chronoamperometry, electrochemical impedance spectroscopy. A 50% share of Co in the matrix developed by EG reduction was found to derive superb catalytic output for EOR and exhibit remarkable poison tolerance, driving the reaction toward final product formation. Image 1 • PtCo/C catalysts prepared using Ethylene Glycol, Borohydride, Hydrazine reagents. • Ample existence of Co oxide/hydroxide in PtCo-EG matrix provides discrete morphology. • Catalytic intervention of transition metal/metal oxides accelerates EOR kinetics. • Estimation of oxidation products on Pt 59 Co 41 /C-EG follow the order CO 3 2- > CH 3 COO-. • In-house DEFC with Pt 59 Co 41 /C-EG anode produces 32.55 mW cm-2 power density. [ABSTRACT FROM AUTHOR]

Abstract A parametric study was carried out to investigate the effect of fuel concentration (0.5 M–3.0 M), operating temperature (ambient temperature to 85 °C), flow rate of ethanol (0.5–5.0 mL min−1) and air (100–600 mL min−1) on the direct ethanol fuel cell (DEFC) performance. The operations were conducted in three operational modes, namely, passive, semi passive, and active modes, and power generation were measured. Ethanol crossover was indicated by the carbon dioxide (CO 2) concentration present at the cathode outlet and measured by using a CO 2 analyzer. Results indicated that DEFC performance increased with the increase of ethanol concentration, and ethanol and oxidant flow rate increased with temperature until DEFC reaches the optimum conditions, i.e., concentration and flow rate. Meanwhile, the DEFC performance significantly and proportionally increased with operation temperature and reached values of up to 8.70 mW cm−2 and 85 °C at stable conditions. Furthermore, fuel crossover, that is, ethanol flux, increased in proportion to the ethanol concentration, i.e., 3.71 × 10−4 g m−2 s−1 and 8.79 × 10−4 g m−2 s−1 for 0.5 M and 3.0 M ethanol concentration, respectively. At different modes of operation, the active DEFC system exhibited the highest performance, followed by the semi passive and passive DEFC system. These results indicated that optimizing ethanol, oxidant flow rate and temperature would enhance the mass transport in anodes and cathodes, and hence improve the electrochemical reactions and DEFC performance. Highlights • Effects of operating parameters on the cell performance and fuel crossover. • Optimums of operating parameters are needed for obtaining high performance. • Cell was operated in passive, semi-passive and active modes. • Increasing fuel concentration will increase fuel crossover at cathode. [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 understanding of electrocatalytic activity and poisoning resistance properties of Pt and Pd nanoparticles, recognized as the best electrocatalysts for the ethanol oxidation reaction, is an essential step for the commercialization of direct ethanol fuel cells (DEFCs). In this paper, mono and bimetallic Pt and Pd nanoparticles with different atomic ratios have been synthesized to study their electrocatalytic properties for an ethanol oxidation reaction in alkaline solutions. The different nanoparticles were physiochemically characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The electrochemical characterization was performed by cyclic voltammetry and chronoamperometry measurements. The electrochemical measurements indicate that Pt nanoparticles have much higher electrocatalytic activity for ethanol oxidation than Pd nanoparticles. The studies with bimetallic PtPd nanoparticles showed a significant impact of their composition on the ethanol oxidation. Thus, the highest electrocatalytic activity and poisoning resistance properties were obtained for Pt3Pd2 nanoparticles. Moreover, this study demonstrates that the poisoning of the catalyst surface through ethanol oxidation is related to the prevalence of the acetaldehyde–acetate route and the polymerization of acetaldehyde through aldol condensation in the alkaline media.

In this work, prismatic NiO(OH)/CeO@Ce(OH) 3 and nanoporous NiCe–O composites are constructed on the surfaces of the Ce-containing alloy ribbons by dealloying. These freestanding dealloyed samples exhibit excellent performance toward ethanol electrooxidation. Especially, the dealloyed Ti 50 Ce 10 Ni 40 ribbon shows a high current density of 229.4 mA cm−2 (1.6 V vs. RHE). Meanwhile, it also shows outstanding durability with the faradaic current decreasing to ca. 88% within the first 40 s, while remains ca. 84% even after 10 h-long measurement. The enhanced catalytic activity can be attributed to the quadrangular prism (NiO(OH)) array and polygon prisms (CeO@Ce(OH) 3) on the dealloyed Ti 50 Ce 10 Ni 40 ribbon surface with abundant active sites and defects facilitating the adsorption of reactive species, electron transport, and reaction kinetics. This work provides a new perspective for the design of high-active binder-free non-noble electrocatalysts based on multicomponent alloys. [Display omitted] • Nickel Oxyhydroxide/Oxide-based composites were fabricated by dealloying Ce-containing alloy ribbons. • Novelty prismatic NiO(OH)/CeO@Ce(OH) 3 composite were prepared by hydrothermal dealloying. • NiO(OH)/CeO@Ce(OH) 3 composite with rich active sites and defects show high activity and long service life toward ethanol electrooxidation. Developing inexpensive and highly active ethanol electrooxidation catalysts with long service lives for direct ethanol fuel cells is an urgent task. Herein, prismatic NiO(OH)/CeO@Ce(OH) 3 and nanoporous NiCe–O composites are fabricated on the surfaces of Ce-containing alloy ribbons via one-step dealloying, demonstrating excellent catalytic performance for the ethanol oxidation reaction (EOR). Particularly, the Ti 50 Ce 10 Ni 40 ribbon dealloyed for 2 h at a hydrothermal temperature of 140 °C exhibits a high current density of 229.4 mA cm−2 (1.6 V vs. the reversible hydrogen electrode) and maintains outstanding performance for 10 h without apparent deterioration, outperforming most state-of-the-art non-noble catalysts. This phenomenon is associated with the formation of a prismatic NiO(OH)/CeO@Ce(OH) 3 array structure on the alloy ribbon surface with abundant active sites and defects, enhancing the catalyst activity and stability. This study may provide new opportunities for designing and fabricating inexpensive and robust catalysts with excellent performance and a wide range of practical applications. [ABSTRACT FROM AUTHOR]

Alkaline direct ethanol fuel cells are promising future energy technologies with a high energy-density, while the lack of robust anodic electrocatalysts limits their energy conversion efficiency due to serious poisoning and weak selectivity to the C1 pathway of ethanol oxidation reaction (EOR). Herein, rhodium-bismuth alloy nanodendrites (RhBi-NDs) are applied as an efficient and anti-poisoning electrocatalyst for EOR, which exhibit superior electrocatalytic performance, including a mass activity of 1068.9 mA mg Rh −1 at 0.71 V, a 31.1% Faradaic efficiency for the C1 product, and an excellent stability of 40 h. The mechanism study indicates that Bi improves the oxidation ability of Rh to toxic intermediates by providing oxygen-containing species. The theoretical calculations disclose the electronic interaction between Bi and Rh, which tunes the adsorption energy of intermediates such as CH 3 CH 2 OH*, and CH 3 CO*, resulting in the suppression of C2 pathway and the promotion of C1 pathway for EOR on RhBi-NDs. [Display omitted] • RhBi-NDs are reported as a robust and anti-poisoning non-Pt/Pd-based EOR catalyst. • RhBi-NDs have a mass activity of 1068.9 mA mg Rh −1 at 0.71 V for EOR. • A 31.1% F C1 and a stability of 40 h for EOR are achieved on RhBi-NDs. • DFT calculations reveal the tuned adsorption behavior and EOR pathway on RhBi-NDs. [ABSTRACT FROM AUTHOR]

• The electrochemical performance of the Car/PVA-GO membrane is influenced by membrane selectivity. • The highest membrane selectivity of PEMs is 1.609 × 104 S s cm−3. • The maximum power density of passive DEFCs is 14.5 mW cm−2. • The membrane has been sustained for 1000 h without degrading the membrane stability. A good electrochemical performance of polymer electrolyte membranes (PEMs) is achieving high membrane selectivity, which is a result of low ethanol permeability and high proton conductivity. Reducing the thickness of PEMs is beneficial for high proton conductivity due to the short distance of proton diffusion. Unfortunately, it results in high ethanol permeability. Thus, achieving high membrane selectivity for good electrochemical performance by balancing the requirements of ethanol permeability and proton conductivity is a critical parameter of PEMs. In this paper, the thickness of the carrageenan/polyvinyl alcohol-graphene oxide membrane was varied from 15 μm – 30 μm to identify the optimum thickness for good electrochemical performance. With a 25 μm membrane thickness, the highest membrane selectivity was performed at 1.609 × 104 S s cm−3, and maximum power density in passive direct ethanol fuel cells was achieved at 14.5 mW cm−2, using 2.0 mg cm−2 anode catalyst loading and 2 M ethanol concentration at 70 °C, respectively. Furthermore, this membrane has sustained electrochemical performance for 1000 h at 70 °C without degrading the membrane stability. [ABSTRACT FROM AUTHOR]

• When the height shrinkage rate of the channel is controlled at 55–77%, the current density increases greatly. • The width shrinkage rate has little effect on the performance of the DEFC. • Increasing the height shrinkage rate is beneficial to the discharge of water. • It has an adverse impact on the uniformity of current density distribution when the channel width shrinks. Design and optimization of channel has significant effects on mass and heat transfer and comprehensive performance of fuel cells. In this study, a new type of direct ethanol fuel cell with tubular structure is proposed, and the effects of different channel height and width shrinking rate on the current density, water distribution, temperature distribution and pressure distribution on the cathode side of the cell are studied by computational fluid dynamics (CFD). The results indicate that the height shrinking rate is beneficial to increase the pressure drop on the cathode side and improve the removal ability of water, leading to better fuel cells, and the height shrinking rate is 55–77%, the performance of DEFC is improved the best. When the height shrinking rate is 77%, its optimizations have a power density growth rate of 34%, which is about 31.5 mW/cm2.The width shrinking rate has little effect on the fuel cell, reducing the power density to 23.5 mW/cm2. This phenomenon is due to that the reduction of the Catalytic area leads to the oxygen gradient distribution in the Electrode layer, which promotes the discharge of cathode water, but leads to insufficient oxygen in the central region of the fuel cell membrane electrode, resulting in the decrease of current density. [ABSTRACT FROM AUTHOR]

Metal-Organic Frameworks (MOFs) have offered a new superior choice for designing the distribution of metal mixtures in carbon substrates for energy applications. Herein, the Co-MOF, Cu-MOF, and CoCu-MOF have been synthesized and characterized by Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, Brunauer–Emmett–Teller (BET), and X-ray photoelectron spectroscopy (XPS) techniques. The performance of the as-prepared electrocatalysts was studied in ethanol oxidation reaction (EOR) through cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP), and electrochemical impedance spectroscopy (EIS) methods. The cyclic voltammetry results showed that CoCu-MOF has a much higher ethanol oxidation current density (9.22 mA cm−2) compared to Co-MOF (0.55 mA cm−2) and Cu-MOF (0.28 mA cm−2). As was expected, all the half-cell electrocatalytic measurement results showed that the CoCu-MOF has higher efficiency and best durability toward EOR. Based on half-cell results and the unique characteristics of carbon felt (CF), CoCu-MOF was arrayed on highly conductive three-dimensional (3D) CF (CoCu–MOF/CF) as support by the in-situ solvothermal method. The CoCu-MOF/CF used as a novel binder-free low cost anode electrode in the direct ethanol fuel cell (DEFC). The result of single-cell studies exhibited that the CoCu-MOF/CF in a DEFC operating at 60°C delivered a 0.865 V open-circuit potential and 22.85 mW cm−2 power density. The structural advantages such as 3D architecture, abundant active sites, and the synergistic effect between Co and Cu resulted in the impressive electrocatalytic activity of CoCu-MOF for EOR behavior. Therefore, this study would open a new facial approach to designing effective MOF-based electrocatalysts as efficient catalyst support for direct liquid fuel cells. • CoCu-MOF is decorated on carbon felt by an in-situ method. • Noble-metal-free CoCu-MOF/CF is a binder-free electrode for EOR. • The 3D/3D architecture of CoCu-MOF/CF provides abundant redox active sites. • CoCu-MOF/CF delivers a maximum power density of 22.85 mW cm−2 in DEFC. [ABSTRACT FROM AUTHOR]

Spherical mesoporous NiO powders were synthesized by a hydrothermal-thermal decomposition method, and their morphology and structure were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and N2 adsorption/desorption analysis. The electrocatalytic performance of NiO powders were systematically studied by cyclic vohammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). It is found that the prepared mesoporous NiO powders are in spherical morphology with a specific surface area of 35 m2·g-1 and an average pore size of 15.88 nm. They show good electrocatalytic activity for ethanol oxidation; the oxidation current increases with increasing ethanol concentration and scan rate. The current decay at 0.60 V for 1000 s is as low as 0.075%, indicating good stability. CV, CA and EIS measurements show that ethanol oxidation reaction on the spherical mesoporous NiO is a diffusion-controlled process.

The electrooxidation kinetics of ethanol is key to making direct ethanol fuel cells and electrocatalytically reforming ethanol viable technologies for a more sustainable energy conversion. In this study, the electrooxidation of ethanol was investigated on nickel hydroxide (Ni(OH)2) catalysts synthesized using a facile solvothermal method. Variations in the temperature, heating time, and the addition of oleylamine in the precursor enabled the phase and morphology control of the catalysts. X-ray diffraction and scanning electron microscopy show that the addition of oleylamine in the precursor resulted in microspheres with a high surface area, but favored the formation of β-phase Ni(OH)2. Elevated temperatures or prolonged periods of heating in a controlled environment, on the other hand, can lead to the formation of the ethanol oxidation reaction-active α-phase. Among the synthesized catalysts, the α-Ni(OH)2 microspheres with nanoflakes achieved the highest activity for ethanol oxidation with a current density of 24.4 mA cm−2 at 1.55 V (vs. RHE, reversible hydrogen electrode) in cyclic voltammetry tests and stable at 40 mA cm−2 in chronoamperometric tests at the same potential, comparatively higher than other Ni-based catalysts found in the literature. While the overpotential is beyond the useful range for direct ethanol fuel cells, it may be useful for understanding the mechanism of ethanol oxidation reactions on transition metal hydroxides at their oxidizing potential for ethanol electroreforming.

Direct ethanol fuel cells (DEFCs) have emerged as promising and advanced power systems that can considerably reduce fossil fuel dependence, and thus have attracted worldwide attention. DEFCs have many apparent merits over the analogous devices fed with hydrogen or methanol. As the key constituents, the catalysts for both cathodes and anodes usually face some problems (such as high cost, low conversion efficiency, and inferior durability) that hinder the commercialization of DEFCs. This review mainly focuses on the most recent advances in nanostructured catalysts for anode materials in DEFCS. First, we summarize the effective strategies used to achieve highly active Pt- and Pd-based catalysts for ethanol electro-oxidation, including composition control, microstructure design, and the optimization of support materials. Second, a few non-precious catalysts based on transition metals (such as Fe, Co, and Ni) are introduced. Finally, we outline the concerns and future development of anode catalysts for DEFCs. This review provides a comprehensive understanding of anode catalysts for ethanol oxidation in DEFCs.

In this paper, a catalyst of hollow PdCu alloy nanocubes supported on nitrogen-doped graphene support (H-PdCu/ppy-NG) is successfully synthesized using a simple one-pot template-free method. Two other catalyst materials such as solid PdCu alloy particles supported on this same nitrogen-doped graphene support (PdCu/ppy-NG) and hollow PdCu alloy nanocubes supported on the reduced graphene oxide support (H-PdCu/RGO) are also prepared using the similar synthesis conditions for comparison. It is found that, among these three catalyst materials, H-PdCu/ppy-NG gives the highest electrochemical active area and both the most uniformity and dispersibility of H-PdCu particles. Electrochemical tests show that the H-PdCu/ppy-NG catalyst can give the best electrocatalytic activity and stability towards the ethanol electrooxidation when compared to other two catalysts. Therefore, H-PdCu/ppy-NG should be a promising catalyst candidate for anodic ethanol oxidation in direct ethanol fuel cells.

Abstract The current study reports the preparation and investigation of several Pt-based anode catalysts loaded on reduced graphene oxide (rGO) as electrocatalysts in both acid and alkaline media for ethanol electrooxidation. The synthesized catalysts are evaluated by the method of XRD, Raman spectroscopy, XPS and TEM. Electrocatalytic properties of these catalysts for ethanol oxidation were investigated by cyclic voltammetry and chronoamperometry. It was found that the as-prepared nanocatalysts doped by metals and oxide metals showed the improvement of catalytic performance compared to Pt-only supported on graphene catalyst. The results indicated that the presence of Al favoured Pt nanoparticles dispersing on the surface of rGO sheets. Indeed, the PAG catalyst exhibits the highest mass activity for the ethanol oxidation of 1194 mA mg−1 Pt in acid medium and 3691 mA mg−1 Pt in alkaline medium. In addition, the PAG catalyst also shows good antipoisoning ability for ethanol electrooxidation in both media. This catalyst could be a potential catalyst for direct ethanol fuel cell (DEFC). Highlights • Graphene-supported Pt-based multimetallic catalysts were successfully synthesized. • Electrocatalytic performances of catalysts were examined in acid and alkaline media. • Catalyst containing Pt and Al shows the best electroactivity for ethanol electrooxidation. • Promotion effect of catalysts should be attributed to the presence of AlOOH. • Durability of PtAl-based catalyst was evaluated in both media. [ABSTRACT FROM AUTHOR]

Highlights • Design and fabrication of BPP is further introduced based on our previous study. • Round corner and clearance of moulds play important role in maximum channel height. • Channel dimensions are selected by formability model and reaction efficiency. • Channel height, channel thickness and effect of blank holder are discussed. • Performance of single cell and short stack is tested to evaluate method reliability. Abstract This study offers an efficient design method of flow channels of metallic bipolar plates (BPPs) to improve manufacturing technique of BPPs and maximize power density in proton exchange membrane (PEM) fuel cells. Stamped thin metallic BPPs with anticorrosive and conductive coating are promising candidates for replacing conventional carbon-based BPPs. Nevertheless, unlike carbon-based BPPs, the flow channel design of metallic BPPs should take into account not only the reaction efficiency, but also formability due to the possible rupture of the metallic channel during the micro-forming process. In our previous study, a forming limit model was first proposed to predict the maximum allowable channel height by the forming process. This study is conducted to further propose the method of the design and fabrication of metallic BPPs based on the numerical model. In order to determine channel geometry design from formability perspective, response surface method is utilized to build a formability model. Combining the formability model and reaction efficiency, flow field design for metallic BPPs (channel width of 0.9 mm, rib width of 0.9 mm, channel depth of 0.4 mm and radius of 0.15 mm) is proposed. Experiments on BPP fabrication and assembled 20-cell fuel cell testing are conducted to observe forming quality of micro channel and output performance on the real fuel cell. It is shown that the stamping force grows with increasing channel depth in a nonlinear manner and a blank holder is needed to eliminate the sheet wrinkle in the forming process. The uniformity of the voltage distribution in the 1000 W-class stack further proves the reliability of metallic BPPs designed by our method. The methodology developed is beneficial to the fabrication management of metallic BPPs and effective supplement to the channel design principle for PEM fuel cells. [ABSTRACT FROM AUTHOR]

The catalyst for direct ethanol synthesis (DES) from syngas was investigated in this work, which is Co/La 2 O 3 -doped La 4 Ga 2 O 9 . The catalyst was prepared by using LaCo 1−x Ga x O 3 with perovskite phase as the precursor to intensify the interaction in the elements of Co, La and Ga. The catalysts were characterized by using XRD, H 2 -TPR, TEM, EDS, XPS, BET, ICP and TG techniques. This catalyst showed high selectivity to ethanol and excellent stability including excellent resistance to sintering and carbon deposition. It seems that the ethanol is generated in the interface between metallic Co and La 4 Ga 2 O 9 , and in the interface cobalt would be positively charged due to the interaction between Co nanoparticles and La 4 Ga 2 O 9 . The results and the related discussions indicate that Co/La 2 O 3 -doped La 4 Ga 2 O 9 catalyst is a promising catalyst for DES from syngas. Graphical abstracts. [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]

Graphical abstract Highlights • Three-dimensional modeling of the reactive flow in a DEFC. • The model considers variable concentration of species at the anode and cathode. • Calculation of species concentration according to current density. • DEFC voltage for Pt-Re-Sn/t-MWCNCTs, Pt-Ru/MCN and Pt-Re-Sn/MCN catalysts. • Voltage comparison using temperatures of 353 K, 363 K and 373 K. Abstract In this paper, we use a three-dimensional mathematical model to analyze the flow in a direct ethanol fuel cell (DEFC). The overpotential losses are estimated based on the operating parameters of the cell, and based on the reactive flow within the channels, in the diffusion layer, and on the electrocatalyst surface. The model includes fuel consumption and the formation of acetic acid and acetaldehyde, and the rate of ethanol crossover through the membrane. The numerical simulation of the reactive flow was made based on the central finite difference method. The equations were discretized in time using the Crank–Nicolson method. The model calculates the flow velocity and species concentration along the inlet channel, the diffusion layer and the catalyst surface. The molar fraction of the species is calculated according to the current density in the DEFC. The results for the cell voltage versus current density were obtained for different catalysts on the anode side, for three temperatures and two initial concentrations of ethanol. The results obtained are consistent with the experimental data found in the literature. [ABSTRACT FROM AUTHOR]

The fuel cell is an electrochemical device that converts chemical energy directly into electricity and is more efficient than traditional power generators. In this work, we developed a mathematical model for a direct ethanol fuel cell (DEFC), which considers the flow and concentration of species dependent on time and space for the calculation of losses overpotentials. In addition, the concentration of each species is modeled according to the current density of the DEFC. The finite element method is used to calculate the flow and concentration of the species in different layers of the cell (inlet and outlet channels, diffusion layer and catalyst layer). The model takes into account the losses overpotentials at the anode and at the cathode and the passage of ethanol through the membrane. The voltage and power density of the cell are calculated with different catalysts, temperatures and concentrations of ethanol. A result is shown for limiting current density for low ethanol concentrations. The results obtained compare favourably with the data found in the literature. [ABSTRACT FROM AUTHOR]

The present investigation deals with the comparative analysis of electro-catalytic behaviour of Pt, Pd and ternary combinations of Co and Ni with Pd NPs, supported on vulcan XC72 as the anode component in direct ethanol fuel cell (DEFC) operating in alkaline environment. Catalyst NPs were synthesized by ethylene glycol reduction method and their structure, composition and surface morphology were determined through XRD, EDAX and TEM techniques. The superb catalytic efficiency of PdCoNi/C toward ethanol oxidation reaction (EOR) is ascribed to the catalytic intervention of transition metal ad atoms and their surface oxides, culminating to enhanced electrochemical surface area, preferred OH − adsorption on the surface and remarkable yield of oxidation products (CH 3 CO 2 − and CO 3 2 − ) estimated by ion chromatography. The performance output parameters collectively substantiate not only to the catalytic superiority of the PdCoNi/C catalyst but also affordability to a considerable extent over both the Pt/C and Pd/C catalysts. [ABSTRACT FROM AUTHOR]

Carbon-supported Pd, Pt, Pt1Pd1, and Pt3Pd1 electrocatalysts were prepared by metal ion chemical reduction with borohydride. The electrocatalysts were analyzed by EDS, HRTEM, and XRD techniques. The EDS spectra showed that the actual compositions of the materials were close to the nominal compositions. The XRD measurements revealed that the materials were crystalline, and no oxide peaks were observed. The HRTEM micrographs showed homogeneous particle distributions on the carbon, with Gaussian particle size distributions. The mean particle sizes were taken as the maxima of the Gaussian distributions. All the materials presented electrochemical activities for the ethanol oxidation reaction, with the exception of Pd in acid media. Pt showed poor performance in alkaline media. The poisoning rate was determined by cyclic voltammetry (iforward/ibackward ratios), as well as by chronoamperometry experiments, both of which indicated a low poisoning rate for Pd in alkaline medium and higher poisoning rates as the Pt content increased in the PtPd electrocatalyst [ABSTRACT FROM AUTHOR]

Direct ethanol fuel cells (DEFCs) are considered a viable alternative power source for both stationary and mobile applications. Obstacles to widespread use of DEFCs include the slow electro-oxidation kinetics of ethanol, which has been countered by employing combinations of noble metals and organic compounds as catalysts, e.g., a platinum alloy and perylene-3,4:9,10-tetracarboxylic acid derivatives (PDIs). This study investigates the performance of a PDI functionalized with 4-amino pyridine (PDI1) and subsequently dispersed in Pt/C (Pt/C/PDI1) and PtSn/C (PtSn/C/PDI1). The performance of these catalysts in ethanol electro-oxidation (EOR) was compared to that of metallic catalysts (PtSn/C and Pt/C). The forward potential scan indicated that the peak current densities (j) on the catalysts Pt/C/PDI1 and PtSn/C/PDI1 were ~ 1.7 and ~ 1.3-fold that of Pt/C and ~ 1.8 and ~ 1.4-fold that of PtSn/C. Concerning ethanol oxidation, this indicates that Pt/C/PDI1 and PtSn/C/PDI1 exhibit better catalytic activity in EOR than Pt/C and PtSn/C do. [ABSTRACT FROM AUTHOR]

Direct ethanol fuel cells are one of the most promising electrochemical energy conversion devices for portable, mobile and stationary power applications. However, more efficient and stable and less expensive electrocatalysts are still required. Interestingly, the electrochemical performance of the electrocatalysts toward the ethanol oxidation reaction can be remarkably enhanced by exploiting the benefits of structural and compositional sensitivity and control. Here, we describe the synthesis, characterization, and electrochemical behavior of cubic Pt-Sn nanoparticles. The electrochemical activity of the cubic Pt-Sn nanoparticles was found to be about three times higher than that obtained with unshaped Pt-Sn nanoparticles and six times higher than that of Pt nanocubes. In addition, stability tests indicated the electrocatalyst preserves its morphology and remains well-dispersed on the carbon support after 5000 potential cycles, while a cubic (pure) Pt catalyst exhibited severe agglomeration of the nanoparticles after a similar stability testing protocol. A detailed analysis of the elemental distribution in the nanoparticles by STEM-EELS indicated that Sn dissolves from the outer part of the shell after potential cycling, forming a ~0.5 nm Pt skin. This particular atomic composition profile having a Pt-rich core, a Sn-rich subsurface layer, and a Pt-skin surface structure is responsible for the high activity and stability. [ABSTRACT FROM AUTHOR]

Abstract: Pt‐Sn‐Eu catalysts were synthesized by modified polyol method, evaluated for the ethanol oxidation reaction (EOR), and compared to commercial Pt/C and Pt‐Sn/C catalysts. The catalysts were electrochemically characterized in both three‐electrode and fuel cell setups. X‐ray diffraction measurements indicated some degree of Pt‐Sn alloying in the Pt‐Sn‐Eu/C catalysts, and mean crystallite sizes between 2.3–3.3 nm, while X‐ray photoelectron spectroscopy measurements showed the presence of Pt and Sn in both metallic and oxide form, and rare earth metals in the form of mixed oxides. Adding tin and europium promoted filling of the Pt 5d band, as confirmed by X‐ray absorption. The electrochemical characterization showed a higher oxidation current density and lower oxidation onset potential for the ternary Pt‐Sn‐Eu materials compared with the commercial catalysts, in both the three‐cell and fuel cell tests. High performance liquid chromatography measurements indicating that the main products of ethanol oxidation were acetaldehyde and acetic acid; a low concentration of CO2 was also detected. The improved ethanol oxidation efficiency for the Pt‐Sn‐Eu/C catalysts can be explained by the Sn/Eu‐Pt electronic effect, because it weakens the adsorption of intermediate products by Pt, and favors the bifunctional EOR mechanism, as europium oxide renders oxygenated species available at lower potentials. [ABSTRACT FROM AUTHOR]

A size customized binder-free bimetallic Pd-Pt loaded graphene aerogel deposited on nickel foam plate (Pd-Pt/GA/NFP) was prepared and used as an electrode for an alkaline direct ethanol fuel cell (DEFC) under room temperature. The effect of fuel concentration and metal composition on the output power density of the DEFC was systematically investigated. Under the optimum fuel concentration, the cell could achieve a value of 3.6 mW cm −2 at room temperature for the graphene electrode with Pd/Pt ratio approaching 1:1. Such results demonstrated the possibility of producing a size customized metal loaded GA/NFP electrode for fuel cell with high performance. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells (SOFCs) based on conventional nickel-yttria stabilised zirconia (Ni-YSZ) anodes can not be fed directly with organic fuels because of the associated formation of carbon deposits. This work explores a simple approach to solve such relevant limiting factor that affects the direct utilization of conventional dry hydrocarbons in SOFCs. The approach consists in depositing a composite multifunctional electrocatalyst layer on the SOFC anode to work as an internal integrated fuel processor. This study investigates the direct oxidation of dry ethanol in the modified SOFC and provides an evaluation of cell performance. A protective layer based on a composite made of Ni-modified perovskite and gadolinia-doped ceria is coated on a conventional SOFC anode based on Ni-YSZ. Besides the oxygen storage properties of ceria, the composite electrocatalyst is characterized by the presence of dispersed Ni-alloy @ FeOx core-shell nanoparticles in the outer layers and surface basicity properties. Efficient dehydrogenation of ethanol, carbon deposition-free cracking reactions and internal reforming assisted by a H 2 /H 2 O “shuttle mechanism” appear as the key steps involved in the direct oxidation of the organic fuel at the modified SOFC anode. The best performance achieved for the dry ethanol-fed SOFC is about 0.65 W cm −2 at 0.6 V and 800 °C. No carbon deposition is observed both on the Ni-YSZ supporting layer and protective Ni-doped perovskite layer after a durability test of more than 100 h. [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]

The synthesis of Pt + SnO 2 /C electrocatalyst containing cubic Pt nanoparticles with preferential (100) orientation was performed by an alcohol-reduction process using KBr as a shape directing agent. The order of addition of the Pt and Sn precursors and KBr was crucial to obtain cubic Pt particles and a SnO 2 phase with small particle sizes highly dispersed on the carbon support. Electrochemical and DEFC experiments showed that Pt + SnO 2 /C electrocatalyst containing Pt nanoparticles with preferential (100) orientation provided superior activity for EOR, power densities and CO 2 selectivity compared to Pt + SnO 2 /C electrocatalyst containing Pt polycrystalline. [ABSTRACT FROM AUTHOR]

Pd-based electrocatalysts with advanced activity and durability can greatly accelerate the commercial process of direct ethanol fuel cells (DEFCs). However, Pd nanoparticles (NPs) are easily aggregated and deactivated during the ethanol oxidation reaction (EOR), which will restrict their electrocatalytic efficiency during the long-term running. To solve these problems, we develop new sandwich-like MXene-based N-doped porous carbon (NPCM) through carbonizing and acid etching of ZIF/MXene composite nanosheets. The derived NPCM nanosheets possess a highly ordered nano-porous and N-doped structure, which can be used as competitive catalyst supports to highly disperse Pd NPs and effectively avoid the aggregation and deactivation of Pd NPs. Meanwhile, the as-synthesized Pd/NPCM can offer more activity sites and more space for electrocatalysis reaction, leading to excellent CO tolerance. Thanks to the combination of MXene and ZIF, the designed Pd/NPCM electrocatalyst can offer connected channels for the fast diffusion of reactants and products. Impressively, the Pd/NPCM electrocatalyst exhibits a mass activity of 2237 mA·mg Pd −1, which is 1.90 and 6.37 folds that of Pd/ZIF (1179 mA mg Pd −1) and Pd/C (351 mA mg Pd −1) electrocatalyst, respectively. This work not only explores a novel strategy for preparing advanced electrocatalyst support materials but also opens up their wide applications in DEFCs. [Display omitted] • A novel sandwich-like MXene-based N-doped porous carbon (NPCM) nanosheet was prepared. • The unique sandwich structure can effectively avoid the aggregation and deactivation of Pd NPs. • The designed Pd/NPCM electrocatalyst can offer connected channels for the fast diffusion of reactants and products. • Pd/NPCM electrocatalyst exhibits excellent catalytic activity for ethanol oxidation reaction. [ABSTRACT FROM AUTHOR]

Selective breaking of the C-C bond in ethanol holds the key to many industrial processes, including the operation of direct ethanol fuel cells and steam reforming. Interstitial C atoms in the subsurface region of noble-metal catalysts have major impacts on the selectivity and activity, but an understanding of the mechanistic details is still elusive due to their nature of in situ formation and metastability. Herein, we develop a method to obtain stable RhC x (x ≈ 0.5) by introducing C atoms into the interstitial sites of well-defined Rh nanosheets of 8–10 at. layers in thickness, and further elucidate the electronic and geometric effects of the interstitial C atoms on the cleavage of C-C bond. With the introduction of C atoms into half of the octahedral sites, the Rh lattice changes from a cubic to an orthorhombic structure. The lattice expansion induced by the insertion of C atoms, together with the electron transfer between C and Rh atoms, effectively suppresses the coupling reaction between OH* and CH 3 CO* to form acetic acid while making the cleavage of C-C bond more exothermic. As such, we obtain a selectivity of ethanol to CO 2 as high as 18.1 %, much higher than those of the Rh counterpart (10.0 %), together with 3.1-fold improvement in kinetics. Guided by these findings, a new method is also developed to directly introduce C atoms into the subsurface of a commercial Rh black to enhance its selectivity and activity by 2.5- and 1.6- folds, respectively. [Display omitted] • Interstitial C atoms are introduced into the well-defined Rh nanosheets and the crystal structures are clearly resolved. • The electron transfer and the expanded lattice enhance both selectivity and activity for the cleavage of C-C bond in ethanol. • The insights are further utilized to directly modify the commercial Rh black to greatly improve its catalytic properties. [ABSTRACT FROM AUTHOR]

• A standalone nickel sulfide electrode was prepared on the surface of nickel foam. • The electrodes have a highly porous nanosheet structure. • The electrodes demonstrated a high ethanol oxidation activity. • The electrode showed excellent mass transfer properties. • The electrode showed improved charge transfer of the nickel sulfide. Direct alcoholic fuel cells such as DEFCs "direct ethanol fuel cells" have a high energy density and can potentially replace secondary batteries in portable applications. Two main challenges of the DEFCs are the low efficiency and the precious/expensive Pt-based electrodes. In this study, a standalone nickel sulfide electrode was grown on the surface of nickel foam via hydrothermal method followed by hydrothermal ion exchange. The prepared electrodes have a highly porous nanosheet structure and demonstrated high ethanol oxidation activity. The electrode showed high stability and excellent mass transfer properties with a constant generation of current density of 100 mAcm−2 at 0.5 V, two times that of the Ni-layered double hydroxide and ten times that of nickel foam. The superior activity was due to the enhanced charge transfer of the nickel sulfide (confirmed by EIS (electrochemical impedance spectroscopy)) and the improved mass transfer of the highly porous nanosheet structure. [Display omitted] [ABSTRACT FROM AUTHOR]

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

Ethanol is a promising future fuel for Direct Alcohol Fuel Cells (DAFCs) and one of the significant half-cell reactions of this type of FC is ethanol oxidation reaction (EOR). However, the high cost, low selectivity of the catalyst towards complete oxidation of ethanol to CO 2 , and poor electrode kinetics are the key challenges in commercializing this technology. The way to mitigate these issues is to design affordable, stable, and highly efficient electrocatalysts. In this prospect, we developed a zeolite-carbon (ZSM-5/AC) supported Pd-Ag binary alloy catalysts via a simple co-impregnation followed by co-reduction method. The influence of ZSM-5/AC composite support and its composition on the activity of bimetallic Pd-Ag catalyst has been studied in detail. The PdAg/ZSM-5/AC electrocatalyst with 1:3 wt ratio of ZSM-5:AC exhibited better catalytic performance (10.9 mA cm−2) and tolerance towards intermediate species than PdAg/AC and Pd/AC electrocatalysts. The larger j f /j b (forward to backward current density ratio) of 2.8 for PdAg/ZSM-5/AC indicates lower carbonaceous species accumulation on the zeolite-modified electrode. Additionally, the material possessed a good long-term cyclic stability up to 500 cycles. The high activity observed for PdAg/ZSM-5/AC could be attributed to synergism between bimetallic catalysts and high surface area zeolite support. Overall, the study reveals that the Pd-Ag bimetallic and ZSM-5/AC are potentially efficient electrocatalyst and support, respectively, for the ethanol oxidation reaction in DEFC application. [ABSTRACT FROM AUTHOR]

Current catalysts used for ethanol oxidation reaction (EOR) cannot effectively prevent CH 3 COOH formation, and thus become a major hindrance for direct ethanol fuel cell applications. We report an Ir catalyst that shows great promise for a complete EOR based on density functional theory calculations using PBE functional. The reaction barrier on Ir(1 0 0) was found to be 2.10 eV for CH 3 COOH formation, which is much higher than currently used Pd and Pt, and 0.57 eV for C C bond cleavage in CHCO species, which are comparable to Pd and Pt. The result suggests future directions for studying optimal complete EOR catalysts. [ABSTRACT FROM AUTHOR]

The development of active catalyst for ethanol electrooxidation is a key to improving the power output of direct ethanol fuel cells (DEFCs). In this study, Pt-Sn was supported on SiO 2 embedded carbon nanofiber as active anode catalyst for DEFC by expecting positive interactions between Pt-Sn-SiO 2 . The composite catalyst, Pt 3 Sn 1 /SECNF, showed highest mass activity for the ethanol electrooxidation, which was 3.7 times higher than the activity of the commercial Pt/C (Pt/C com ). The maximum power density of DEFC single cell with the composite catalyst was 3.5 times higher than that with Pt/C com . [ABSTRACT FROM AUTHOR]

High cost and poor stability of catalysts remain major obstacles for the commercialization of direct ethanol fuel cells (DEFCs). In this work, a Pt 9 Rh/TiO 2 C nanostructured catalyst is synthesized via an impregnation-reduction method followed by thermal annealing in N 2 at ambient pressure. X-ray powder diffraction (XRD) and scanning transmission electron microscopy (STEM) are used to characterize the corresponding physico-chemical properties of the as-prepared catalysts. The results reveal that PtRh nanoparticles are uniformly distributed on the TiO 2 C hybrid support material. Cyclic voltammetry, linear scan voltammetry, CO-stripping voltammograms, chronoamperometry and chronopotentiometry methods are employed to investigate their catalytic performance for ethanol oxidation. The results show that the Pt 9 Rh/TiO 2 C produced a current density of 1039.5 mA mg Pt −1 , which are 3.98, 8.31 and 2.43 times higher than Pt/TiO 2 C, Pt/C and Pt 9 Rh/C, respectively. Furthermore, the Pt 9 Rh/TiO 2 C also has greater resistance to CO-poisoning and displays better stability for ethanol oxidation than other catalysts. Pt 9 Rh/TiO 2 C therefore provides a promising material for ethanol oxidation in direct ethanol fuel cells. [ABSTRACT FROM AUTHOR]

Titanium dioxide is emerging as new class of catalyst support for fuel cell reactions. Via pulsed laser deposition, we prepare hierarchically organized and vertically aligned TiO 2 /Pt nanostructured films on microfibrous carbon paper (CP) substrate at room temperature. Microstructural analyses reveal a metal-support interaction between TiO 2 and Pt. Namely; (i) the particles size of Pt on TiO 2 is smaller than those of Pt grown onto carbon paper substrate under similar condition of synthesis and (ii) Pt metallic state is transformed to ionized Pt 2+ and Pt 4+ . Compared to CP/Pt electrocatalyst, the CP/TiO 2 /Pt electrocatalysts (i) oxidize ethanol at much lower potentials, (ii) display superior current peak densities of more than 2.5 times higher by voltammetry, and (iii) steady state current density during long-term stability up to 8 times greater. For portable electronic applications, the binder-free and hierarchical structures of the CP/TiO 2 /Pt electrocatalyst with its planar deposition make it very attractive as anode for direct ethanol fuel cells. [ABSTRACT FROM AUTHOR]

Direct ethanol fuel cells (DEFCs) offer an attractive alternative to fossil fuel-powered devices due to their high energy density and environmental benignity. However, high cost and poor stability of catalysts are still the main obstacles for the commercialization of DEFCs. Herein, a novel catalyst comprising PtRh alloys anchored on carbon nanotubes that decorated with tungsten nitride (Pt 9 Rh-WN/CNTs) was synthesized via impregnation-reduction method and followed by thermal annealing in N 2 . The X-ray powder diffraction (XRD), scanning electron micrograph (SEM) and transmission electron microscopy (TEM) are employed to characterize the corresponding physico-chemical properties of the as-prepared catalysts. Electrocatalytic performance for ethanol oxidation is evaluated by cyclic voltammetry, linear scan voltammetry, CO-stripping voltammograms, chronoamperometry and chronopotentiometry. The current density on Pt 9 Rh-WN/CNTs is 484.8 mA mg Pt −1 , which is much higher than that of Pt 9 Rh/CNTs (305.7 mA mg Pt −1 ) and Pt/CNTs (135.1 mA mg Pt −1 ). Most importantly, the onset potential for CO oxidation on Pt 9 Rh-WN/CNTs is 0.27 V, which is more negative than that on Pt 9 Rh/CNTs (0.37 V) and Pt/CNTs (0.40 V). Therefore, the Pt 9 Rh-WN/CNTs catalyst displays both outstanding catalytic activity and excellent CO-poisoning tolerance for ethanol oxidation. Synergistic effects arising between WN and PtRh alloy along with nitrogen-doping effects of CNTs with ammonia are proposed to contribute to the outstanding performance of this catalyst in ethanol oxidation. [ABSTRACT FROM AUTHOR]

The designing and fabrication of economically viable electro-catalysts for ethanol oxidation reaction (EOR) in direct ethanol fuel cell (DEFC) has been one of the challenging issues over the decades. The present work deals with controlled synthesis of Pd coupled Au nano structure, as the non Pt group of catalysts for DEFC. The catalytic proficiency of bimetallic NPs (2–10 nm) are found to be strongly dependent on the Pd:Au ratio. The over voltage of EOR is considerably reduced by ∼260 mV with 33% of Au content in PdAu composition compared to Pd alone, demonstrating the beneficial role of Au and/or its surface oxides providing oxygen species at much lower potentials compared to Pd. The catalysts are further subjected to electrochemical analysis through voltammetry along with the temperature study on activation parameters. The quantitative determination of EOR products during the electrolysis is carried out by ion chromatographic analysis; vis-a-vis the coulombic efficiency of the product yield were derived from each of the compositions. Furthermore, a strong correlation among catalytic performances and bimetallic composition is established by screening the catalysts in an in-house fabricated direct ethanol anion exchange membrane fuel cell, DE(AEM)FC. The performance testing demonstrates outstanding increase of peak power density (∼40 mWcm −2 , 93%) for the best accomplishment Au (33%) covered Pd (67%) catalyst in comparison with the monometallic Pd. [ABSTRACT FROM AUTHOR]