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Direct ethanol fuel cells (DEFCs) have been widely considered as a feasible power conversion technology for portable and mobile applications. The economic feasibility of DEFCs relies on two conditions: a notable reduction in the expensive nature of precious metal electrocatalysts and a simultaneous remarkable improvement in the anode's long-term performance. Despite the considerable progress achieved in recent decades in Pt nanoengineering to reduce its loading in catalyst ink with enhanced mass activity, attempts to tackle these problems have yet to be successful. During the ethanol oxidation reaction (EOR) at the anode surface, Pt electrocatalysts lose their electrocatalytic activity rapidly due to poisoning by surface-adsorbed reaction intermediates like CO. This phenomenon leads to a significant loss in electrocatalytic performance within a relatively short time. This review provides an overview of the mechanistic approaches during the EOR of noble metal-based anode materials. Additionally, we emphasized the significance of many essential factors that govern the EOR activity of the electrode surface. Furthermore, we provided a comprehensive examination of the challenges and potential advancements in electrocatalytic EOR. [ABSTRACT FROM AUTHOR]

Pd-based catalysts exhibit higher catalytic activity and durability in many electrochemical reactions. However, the electrochemical performance can be further enhanced by fine-tune of the alloy composition. Although binary alloys have been fully studied, the multicomponent alloys are far beyond understanding, which leaves cocktail effect a compromised explanation for the high-entropy alloy. Herein Pd nanosheet-seeded growth was used to synthesize a Pd-Zn-Cd ternary alloy by accurately controlling the Pd-Zn-Cd molar ratio through adjusting the amount of introduced Cd precursor. Through analysis of the crystal phase structure of PdCdZnx and PdZnxCd1−x, the competitive relationship of Zn and Cd in the alloying process with Pd was unveiled: Pd1Cd1 intermetallics (IMC) is thermodynamically favored over Pd1Zn1 IMC in the ternary system. However, the increased structure stability of PdCd over PdZn does not bring about increased durability in the catalytic ethanol oxidation reaction. The morphology selection of Pd seeds is also crucial for the study, as Pd cubes, Pd tetrahedrons, and Pd octahedrons do not form PdZn in the same protocol. The successful alloying through the seeded growth depends on the maximum diffusion depth of foreign atoms into the seed. [ABSTRACT FROM AUTHOR]

The inefficiency of ethanol oxidation reaction (EOR) presents a significant obstacle in harnessing renewable biofuels with high energy density into electricity. Despite efforts, most Pt-based catalysts still suffer from drawbacks such as poor activity and susceptibility to CO poisoning, particularly in acidic conditions. Herein, we employed a physical laser-assisted approach to synthetize a PtPd alloy with a 1:1 atomic ratio. This alloy demonstrates remarkable performance in acidic EOR, boasting a high mass activity of 1.86 A·mgPt−1 and competitive resistance to poisoning. Combining in situ synchrotron radiation infrared spectroscopy with theoretical calculations, we reveal that the synergic interaction between Pt and Pd enhances both the adsorption of OH* intermediate and the dehydrogenation ability of ethanol. This work will prove the feasibility of synthesizing bimetallic alloys by a physical laser-assisted strategy and promote the development of advanced alloy electrocatalysts. [ABSTRACT FROM AUTHOR]

Direct ethanol fuel cell (DEFC) is promising source for mobile and portable applications, but the electrocatalysts are based on metal noble alloys or doping elements to minimize the incomplete ethanol oxidation and poisoning effect. While the main problem persists, this study describes the enhancement of ethanol oxidation reaction by adding graphene (G) to Vulcan XC-72R carbon black (C) metal support, with different C/G ratios. The Graphene was prepared from exfoliated graphite following by dried at ambient temperature. The 60 wt% graphene hybrid support enhances the current density at 5% cyclic voltammetry (CV) and 127% chronoamperometry (CA) higher than carbon pure support in acid electrolyte, whereas in alkaline, graphene (60 wt%) showed the highest electrochemical activity with an increase of current 82% (CV) and 130% (CA). Therefore, we demonstrated the enhancement of the catalyst electrochemical activity in both electrolytes through a simple synthesis method. The 40 wt% carbon and 60 wt% graphene hybrid support achieving higher performance in ethanol oxidation, evidencing a potential application in DEFC. [ABSTRACT FROM AUTHOR]

The potential of metal oxides in electrochemical energy storage encouraged our research team to synthesize molybdenum oxide/tungsten oxide nanocomposites (MoO3/WO3) and their hybrid with reduced graphene oxide (rGO), in the form of MoO3/WO3/rGO as a substrate with relatively good electrical conductivity and suitable electrochemical active surface. In this context, we presented the electrochemical behavior of these nanocomposites as an electrode for supercapacitors and as a catalyst in the oxidation process of methanol/ethanol. Our engineered samples were characterized by X-ray diffraction pattern and scanning electron microscopy. As a result, MoO3/WO3 and MoO3/WO3/rGO indicated specific capacitances of 452 and 583 F/g and stability of 88.9% and 92.6% after 2000 consecutive GCD cycles, respectively. Also, MoO3/WO3 and MoO3/WO3/rGO nanocatalysts showed oxidation current densities of 117 and 170 mA/cm2 at scan rate of 50 mV/s, and stability of 71 and 89%, respectively in chronoamperometry analysis, in the MOR process. Interestingly, in the ethanol oxidation process, corresponding oxidation current densities of 42 and 106 mA/cm2 and stability values of 70 and 82% were achieved. MoO3/WO3 and MoO3/WO3/rGO can be attractive options paving the way for prospective alcohol-based fuel cells. [ABSTRACT FROM AUTHOR]

The anodic electrooxidation of ethanol to value-added acetate is an excellent example of replacing the oxygen evolution reaction to promote the cathodic hydrogen evolution reaction and save energy. Herein, we present a colloidal strategy to produce Ni-Fe bimetallic alloy nanoparticles (NPs) as efficient electrocatalysts for the electrooxidation of ethanol in alkaline media. Ni-Fe alloy NPs deliver a current density of 100 mA·cm−2 in a 1.0 M KOH solution containing 1.0 M ethanol merely at 1.5 V vs. reversible hydrogen electrode (RHE), well above the performance of other electrocatalysts in a similar system. Within continuous 10 h testing at this external potential, this electrode is able to produce an average of 0.49 mmol·cm−2·h−1 of acetate with an ethanol-to-acetate Faradaic efficiency of 80%. A series of spectroscopy techniques are used to probe the electrocatalytic process and analyze the electrolyte. Additionally, density functional theory (DFT) calculations demonstrate that the iron in the alloy NPs significantly enhances the electroconductivity and electron transfer, shifts the rate-limiting step, and lowers the energy barrier during the ethanol-to-acetate reaction pathway. [ABSTRACT FROM AUTHOR]

Effective and stable catalysts toward ethanol oxidation reaction (EOR) is very important for the application of direct ethanol fuel cells (DEFCs). This research reports a facile synthesis of Ni/sepiolite (Ni/SEP) catalyst through incipient wetness impregnation method, which has large amount of active sites and excellent electrochemical activity toward EOR. Through scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), nickel was found to distribute evenly on the fiber structure of sepiolite through ion exchange with the element magnesium without altering the main structure. With a geometric surface area of 0.07 cm2, Ni/SEP had a larger electrochemical surface area 0.44 m2 g−1, lower onset potential of 0.28 V (vs. SCE), higher peak current density (258.5 mA cm−2), and smaller Tafel slope (20 mV dec−1), indicating a superior electrochemical activity toward EOR. Within the experimental conditions, it was observed to be a diffusion-controlled process based on the linear relationship between peak current and root of scan rates, and the reaction could be accelerated by the increase of both C2H5OH and KOH concentrations. Through the study of cyclic voltammetry as well as calculation of apparent activation energy, an electrolytic-chemical (EC) reaction mechanism was suggested with high valence Ni species as the electron transfer carrier. [ABSTRACT FROM AUTHOR]

Improving the complete ethanol electrooxidation on Pd-based catalysts in alkaline media has drawn widely attention due to the high mass energy density. However, the weak adsorption energy of CH3CO* on Pd restricts the C-C bond cleavage. Inspired by the molecular orbital theory, we proposed the d-state-editing strategy to construct more unoccupied d-states of Pd for the enhanced interaction with CH3CO* to break C-C bonds. As expected, the reduced number of eg electrons and more unoccupied d-states of Pd successfully formed on as-prepared porous RhAu-PdCu nanosheets (PNSs). Theoretical calculations show that the optimized d-states of RhAu-PdCu PNS can effectively improve the adsorption of CH3CO* and drastically reduce the energy barrier of C-C bond cleavage, thus boosting the complete oxidation of ethanol. The charge ratio of C1 pathway on RhAu-PdCu PNSs is 51.5%, more than 2 times higher than that of Pd NSs. Our finding provides an innovative perspective for the design of highly-efficient noble-based electrocatalysts. [ABSTRACT FROM AUTHOR]

Tin dioxide-modified Pt electrodes with different coverages ( θ SnO 2 ) were prepared by potentiostatically depositing tin on a Pt electrode in 0.1 M H2SO4 solutions containing various concentrations of SnCl2, followed by oxidizing in air. The θ SnO 2 was controlled by the SnCl2 concentration. The CO-stripping voltammogram of the Pt/SnO2 electrode with θ SnO 2 = 0.61 (Pt/SnO2(0.61)) exhibited two peaks, a prepeak due to the oxidation of adsorbed CO at Pt sites adjacent to SnO2 and a main peak due to that at Pt sites far from SnO2. In the kinetic analysis of both peaks using CO-stripping voltammograms at various sweep rates, the rate-determining steps for the prepeak and main peak were the coupling of adsorbed CO on Pt with OH on SnO2 surface by bifunctional effect and the dissociatively adsorption reaction of water to adsorbed OH on Pt, similar to the Pt electrode, respectively. In the linear sweep voltammograms of Pt/SnO2 electrodes in a (0.1 M HClO4 + 1 M ethanol) solution, the current for ethanol oxidation reaction (EOR) was the highest for θ SnO 2 = 0.61. The analysis of EOR products at different potentials for the Pt/SnO2(0.61) electrode by in situ infrared reflectance-absorption spectroscopy exhibited the Pt/SnO2(0.61) electrode facilitated acetic acid production. Moreover, rhodium was electrochemically deposited on the Pt sites adjacent to SnO2 using the limited CO-stripping technique. The area-controlled Rh deposition did not change the rate-determining steps of both peaks, but it not only enhanced EOR activity, but also decreased acetic acid selectivity and increased CO2 selectivity. [ABSTRACT FROM AUTHOR]

Pt-Sn/C has been widely reported as an anode catalyst in direct ethanol fuel cell (DEFC). However, this bimetallic catalyst often results in the production of a four-electron reaction product (acetate) instead of 12 electrons required for complete ethanol oxidation. In this work, a surfactant-free bromide anion exchange (BAE) method was used for the first time to prepare rare-earth (La, Ce, Pr, and Eu) modified Pt-Sn electrocatalysts for promoting the C-C bond cleavage. Among the synthesized nanomaterials, Pt-Sn-Ce/C exhibited the highest current density and good stability in alkaline medium. X-ray photoelectron spectroscopy (XPS) was used to analyze the surface properties of the synthesized materials and correlate them with electrochemical characterizations to enhance their activity towards ethanol oxidation reaction (EOR). The in situ Fourier transform infrared (FTIR) spectroscopy investigations provided evidence of similar EOR pathways for Pt-Sn and rare-earth modified bimetallic anodes. The presence of the cocatalysts promoted higher current density during the EOR, especially for Pt-Sn-Ce/C. [ABSTRACT FROM AUTHOR]

An organic surfactant/stabilizer plays a critical role in synthesizing small and well-dispersed nanoparticles with large catalytic surface areas. However, a stabilizer typically interferes with the catalytic reaction by forming organic layers on the surface of nanoparticles. Here, we report that the role of a stabilizer can be replaced by the periodic and uniform fluid shear of Taylor vortex flow. Small, well-dispersed PdAg alloy nanoparticles on carbon were synthesized in the continuous Couette-Taylor (CT) reactor in the absence of a stabilizer. The synthesized PdAg nanoparticles (Pd64Ag36/C) showed two times higher mass activity than commercial Pd/C and good stability (retained 33% after 3,600 s) toward the electrochemical ethanol oxidation reaction due to their clean surface and alloy structure. [ABSTRACT FROM AUTHOR]

Given that the size and structure of the catalyst strongly affect its performance during the ethanol oxidation reaction (EOR), here, a series of Ag-core/Pd-shell catalysts are synthesized and characterized. Impressively, the Ag@Pd-2 with the smallest size exhibits superior EOR performance in comparison to the counterparts (Pd, Ag@Pd-0, Ag@Pd-1, and Ag@Pd-3) and a commercial Pd catalyst. Furthermore, the strain and electronic effects also play an important role in enhancing catalytic activity. This work can provide a guide for facilely designing high-performance electrocatalysts for EOR and beyond. [ABSTRACT FROM AUTHOR]

The catalytic performance of Pt-based catalysts depends sensitively on their d-band centers. Nevertheless, there are still huge challenges to evaluate their d-band centers from experimental technologies, and modulate them to analyze their selectivity in ethanol oxidation reaction (EOR). Here, Pt1Au1 alloy supported on the commercial carbon material (Pt1Au1/C) is employed as a typical example to investigate its d-band center shift of surface Pt, and as electrocatalysts to study its selectivity towards EOR. Significantly, a highly reliable in situ Fourier-transform infrared spectroscopy CO-probe strategy is developed to characterize the d-band center shift of surface Pt. The modified electronic effect and site effect of Pt1Au1/C dictated the adsorption configuration of intermediate species and the OH species coverage, thereby influencing its selectivity. More importantly, we developed a universal cyclic voltammetry peak differentiation fitting method as an electrochemical analysis technique to investigate CO2 selectivity, which is potentially extendable to other Pt-based electrocatalysts. [ABSTRACT FROM AUTHOR]

Developing new electrocatalysts with greater catalytic activity and enhanced stability than Pt to power generation is essential due to high demands and decreased fossil fuel reserves. Bimetallic nanoparticles (BNPs) present a synergic effect, showing better and even unique properties than monometallic nanoparticles, but to know their potential, it is a requirement to control their size, morphology, structure, and composition. This work shows the synthesis of PdPt BNPs by chemical reduction in an organic medium. BNPs supported on Vulcan XC-72 carbon showed controlled characteristics, verified by scanning electron microscopy, scanning transmission electron microscopy, and X-ray diffraction techniques. The electrochemical activity was investigated for the ethanol oxidation reaction in alkaline medium by cyclic voltammetry, and the kinetic current was normalized to specific and mass activity. The CO tolerance was explored by chronoamperometry and the evaluation of adsorption and oxidation of intermediates species during the oxidation reaction by alternative CO-stripping analysis. Also, the accelerated durability test showed lower degradation to PdPt/C than the commercial and synthesized Pt/C. According to the results, PdPt/C electrocatalyst exhibits superior catalytic properties, overcoming a limitation in the durability for its potential application in fuel cell technology. [ABSTRACT FROM AUTHOR]

Intermetallic or substitutional solid-solution PdZn alloy nanoparticle (NP)-loaded carbon black (i-PdZn/C, s-PdZn/C) was prepared by reducing equimolar palladium acetate and zinc acetate in ethanol dispersion of carbon black with sodium tetrahydroborate with and without the following heat-treatment in an autoclave. The Pd 3d and Zn 2p core-level spectra exhibited that the binding energy of Pd and Zn for i-PdZn/C shifted positively and negatively compared to that for metallic Pd and Zn sheets, respectively, suggesting a strong electronic interaction between Pd and Zn. In contrast, for s-PdZn/C, the binding energy for Pd shifted positively, but only a peak for ZnO was observed. In 1 M KOH aqueous solution at 20 ºC, the Zn content of s-PdZn/C was almost zero in 30 min, while i-PdZn/C held the Zn component of 75% at 20 ºC and 70% at 60 ºC after 30 min, indicating that i-PdZn/C was much more tolerant to alkaline medium than s-PdZn/C. Consequently, s-PdZn NPs were changed to porous Pd NPs, whereas i-PdZn NPs were changed to core–shell NPs whose surface was porous Pd. In the (1 M KOH + 1 M ethanol) aqueous solution at 20 ºC, i-PdZn/C and s-PdZn/C significantly enhanced the activity for ethanol oxidation reaction (EOR) compared to Pd NP-loaded carbon black (Pd/C). In the potentiostatic electrolysis at 0.7 V for 10,000 s, the deterioration of i-PdZn/C was effectively delayed compared to Pd/C and s-PdZn/C due to the electronic effect of the intermetallic PdZn core. [ABSTRACT FROM AUTHOR]

Although nanostructures based on noble metal alloys are widely used in the anode catalysts of direct ethanol fuel cells, their commercialization remains a remarkable challenge due to their high cost and poor durability. We describe the successful synthesis of trimetallic PtTiMg alloy nanoparticles with adjustable composition using a simple one-step three-target magnetron co-sputtering method. Various physical characterization and electrochemical methods were used to investigate the structure/composition and electrochemical properties of the obtained PtTiMg alloy catalysts toward ethanol oxidation reaction (EOR). The PtTiMg alloy catalyst demonstrated excellent electrocatalytic activity and high durability when the Mg content was 2.76%, (after 3000 cycles, retained 91% of its electrochemical surface area). Furthermore, the electrochemically active surface area and peak current density of the PtTiMg alloy catalyst are 1.5 and 0.8 times higher than those of the commercial pure Pt catalyst, respectively. Furthermore, the long-term strong acid immersion test demonstrated that the PtTiMg alloy catalysts retain high electrocatalytic activity in harsh environments, demonstrating the potential application of the obtained PtTiMg alloy catalysts for EOR. [ABSTRACT FROM AUTHOR]

In the field of noble metal-catalyzed alcohol electro-oxidation reaction (AOR), huge attention is paid on the composition, size, facet, and structure of the metals, while the support engineering should also be emphasized. CeO2 has been widely used as an unique support in AOR, primarily due to its abundant oxygen vacancies (Ov). Herein, we report CeO2·xH2O nanoparticles with both massive hydroxyl groups (OH) and Ov remarkably enhance the catalytic activity and stability of Pd toward ethanol oxidation reaction (EOR). The CO striping experiments and density functional theory (DFT) calculations suggest that OH and Ov on CeO2·xH2O surface bring about a large downshift of Pd d-band center and a significant weakening of CO absorption on Pd. Moreover, OH and Ov also play synergic roles in the removal of toxic intermediates. Consequently, the important roles of OH and Ov of CeO2·xH2O are confirmed in Pd-catalyzed EOR. The facile CeO2·xH2O-enhanced strategy can contribute to the catalyst design for other energy conversion reactions. [ABSTRACT FROM AUTHOR]

Highly active and durable Pd-based electrocatalysts for ethanol oxidation reaction (EOR) play a crucial role in the commercialization of direct ethanol fuel cells (DEFCs). However, the poisonous intermediates (especially adsorbed CO species (COad)) formed during the EOR process can easily adsorb and block the active sites on Pd electrodes, which in turn limits the catalytic efficiency. Hence, we present a series of Pd-based composites with a strong coupling interface consisting of Pd nanosheets and amorphous Bi(OH)3 species. The incorporation of Bi(OH)3 can induce an electron-rich state adjacent to the Pd sites and effectively separate the Pd ensemble, leading to excellent CO tolerance. The optimal Pd-Bi(OH)3 NSs catalyst manifests a mass activity of 2.2 A·mgPd−1, which is 5.7 and 2.0 times higher than that of Pd NSs and commercial Pd/C catalyst, respectively. Further CO-stripping experiments and CO-DRIFTS tests confirm the excellent CO tolerance on Pd-Bi(OH)3 NSs electrode, leading to the enhanced EOR durability. [ABSTRACT FROM AUTHOR]

Gold–palladium (AuPd) alloy nano-corolla are successfully prepared in high purity, followed by exploration as electrocatalysts for electroxidation of ethanol (EOR) in alkaline medium. Applying kinetics control on the one-pot formation process using a syringe pump is emphasized, where the Au/Pd precursor solution is dropwise titrated into the reaction mixture containing capping agent and reductant at an elevated temperature. We perform systematical investigation towards the morphology evolution pathway and effects of several key parameters. After loading on carbon black, the current AuPd alloy nano-corolla exhibit superb specific activity, reaction kinetics, and operation stability for EOR, showing morphological and structural merit. The present study provides insight into fabrication of bimetallic alloy nanocrystals with open structure, which could find important use in crystal engineering for multimetallic nanocrystals and rational design of fuel cell electrocatalyst. Gold–palladium (AuPd) alloy nanocrystals in the form of corolla are successfully prepared via kinetic-controlled synthesis in high purity, exhibit improved activity and stability as EOR electrocatalysts in KOH solution [ABSTRACT FROM AUTHOR]

An in-house synthesized activated biocarbon (aBC) and commercial Vulcan carbon (V) were studied as PdSn catalyst supports for the ethanol oxidation reaction (EOR) in an alkaline medium. The results obtained showed that the PdSn/V electrocatalyst presented much higher catalytic performance than the PdSn/aBC. These results can be associated with the fact that the catalyst particles in the PdSn/V electrocatalyst presented a higher SnO2 concentration compared to PdSn/aBC. The presence of SnO2 has an electronic effect that accelerates the adsorption of ethanol on the surface of Pd, thus enhancing the ethanol oxidation kinetics and contributing to a significant improvement in the PdSn/V catalytic activity. However, no significant differences were observed in the EOR mechanism. [ABSTRACT FROM AUTHOR]

Multilayer graphene (G-US) and multilayer graphene muffled (Gm-US) produced by liquid exfoliation ultrasound were used as support for Pd nanoparticles with a load of 20 wt% for application in an alkaline direct ethanol fuel cell (ADEFC) anode. The multilayer graphene–based electrocatalyst (Pd/G-US) exhibited superior current density and less positive onset potential for ethanol oxidation reaction (EOR) than the commercial Pd/C (AA). Also, the Pd/G-US electrocatalyst showed the less positive onset potential for CO oxidation. In ADEFC experiments, the Pd/G-US catalyst exhibited a superior performance with 38 mW cm−2. The findings suggest that the defective graphene structure promotes electron transport, and the presence of oxygenated species increases hydrophilicity facilitating the oxidation of intermediates. Hence, the synthesized material can be considered as promising support for an anode in ADEFC. [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]

Noble metal alloy nanowires (NWs) with ultrathin diameters (2–3 nm) and precisely controllable elemental compositions have attracted dramatically growing attention for (electro)catalysis. Despites numerous achievements in past two decades, noble metal alloy NWs are mostly synthesized with the traditional oil-phase methods that suffer from some undesirable drawbacks. Here, we report a general strategy for fast, scalable, and aqueous synthesis of multicomponent Pd-based alloy ultrathin NWs with an average diameter of 2.6 nm, ranging from bimetallic PdM (PdFe, PdCo, PdNi, PdCu, PdZn, PdRu, PdRh, PdAg, PdCd, PdIr, PdPt, PdAu) and binary PdS/PdP NWs, to trimetallic PdM1M2 NWs (PdAuCu, PdCoNi, PdCuZn, PdCuNi, PdAgCu, PdAuCu, PdRuAg, PdAuRu, and PdPtAu), and to tetrametallic PdM1M2M3 NWs (PdAuAgCu, PdCoCuNi, PdAuCuNi, PdPtAuCu, and PdIrPtAu). The key to the success of this aqueous synthesis is the utilization of N2H4 as the extremely strong reducing agent that directs the synchronous reduction and anisotropic nucleation growth of multicomponent Pd alloy NWs along nanoconfined columnar phase assembled with amphiphilic dioctadecyldimethylammonium chloride. As-resultant Pd-based alloy ultrathin NWs exhibit multiple structural and compositional synergies, which remarkably optimize the removal of poisoning ethoxy intermediates and thus improve electrocatalytic performance towards ethanol oxidation reaction (EOR). Among them, tetrametallic PdAuCuNi alloy ultrathin NWs hold a high EOR activity of 5.14 A mgPd−1 and a low activation energy of 13.1 kJ mol−1, both of which are much better than its counterpart catalysts alloyed with less elements. This work represents an important advance in precise aqueous synthesis of multicomponent noble metal alloy ultrathin NWs as the high-performance electrocatalysts for various targeted applications. [ABSTRACT FROM AUTHOR]

Branched Au nanocrystals with sub-10-nm arms are synthesized via a one-pot reduction in aqueous phase. The success of current work relies on the use of octadecyltrimethylammonium chloride as the shape-directing capping agent to facilitate the formation of branched products in high purity. Their overall size could be controlled in the range of 16–60 nm by varying the Au precursor amount or concentration of capping agent, and the diameter of arms is limited to sub-10-nm size range. Interestingly, Au nanocrystals with a unique morphology, sheet-wrapped dendrites, could be obtained when the concentration of a reductant was varied. The current strategy is also validated effective in the fabrication of dendritic products composed of other noble metals or alloys in addition to Au by simply using the alternative metal precursor. As compared to spherical counterparts, the current branched Au nanocrystals exhibited noticeable red-shift in UV-Vis extinction spectrum and enhanced catalytic activities for electrooxidation of ethanol in alkaline media. [ABSTRACT FROM AUTHOR]

The catalysis of Au thin film could be improved by fabrication of array structures in large area. In this work, nanoimprint lithography has been developed to fabricate flexible Au micro-array (MA) electrodes with ∼ 100% coverage. Advanced electron microscopy characterisations have directly visualised the atomic-scale three-dimensional (3D) nanostructures with a maximum depth of 6 atomic layers. In-situ observation unveils the crystal growth in the form of twinning. High double layer capacitance brings about large number of active sites on the Au thin film and has a logarithmic relationship with mesh grade. Electrochemistry testing shows that the Au MAs perform much better ethanol oxidation reaction than the planar sample; MAs with higher mesh grade have a greater active site utilisation ratio (ASUR), which is important to build electrochemical double layer for efficient charge transfer. Further improvement on ASUR is expected for greater electrocatalytic performance and potential application in direct ethanol fuel cell. [ABSTRACT FROM AUTHOR]

The widespread application of direct ethanol fuel cells is hampered due to the low activity, high cost and poor operation durability of electrocatalysts for ethanol oxidation reaction (EOR). Herein, we report a one-pot synthetic method to synthesize PdPb3 nanochains with well-defined shape, size and composition via a solution-phase reduction method. The morphology, composition distribution and structure characteristics of PdPb3 nanochains were investigated by transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. Thanks to the unique structure, the as-obtained PdPb3 nanochains can manifest much higher mass activity (2523 mA·mg−1) and higher operation durability than commercial Pd/C (1272 mA·mg−1) during the EOR measurements. More importantly, further CO-stripping measurements indicate that the incorporation of Pb species could favor the oxidative removal of CO intermediates on the Pd electrode at the negative potential and enhance the EOR activity and stability, making it possible to develop highly active and durable electrocatalysts. [ABSTRACT FROM AUTHOR]

Crystal phase can greatly affect the physicochemical properties and applications of nanomaterials. However, it still remains a great challenge to synthesize nanostructures with the same composition and morphology but different phases in order to explore the phase-dependent properties and applications. Herein, we report the crystal phase-controlled synthesis of PtCu alloy shells on 4H Au nanoribbons (NRBs), referred to as 4H-Au NRBs, to form the 4H-Au@PtCu core-shell NRBs. By tuning the thickness of PtCu, 4H-PtCu and face-centered cubic (fcc) phase PtCu (fcc-PtCu) alloy shells are successfully grown on the 4H-Au NRB cores. This thickness-dependent phase-controlled growth strategy can also be used to grow PtCo alloys with 4H or fcc phase on 4H-Au NRBs. Significantly, when used as electrocatalysts for the ethanol oxidation reaction (EOR) in alkaline media, the 4H-Au@4H-PtCu NRBs show much better EOR performance than the 4H-Au@fcc-PtCu NRBs, and both of them possess superior performance compared to the commercial Pt black. Our study provides a strategy on phase-controlled synthesis of nanomaterials used for crystal phase-dependent applications. [ABSTRACT FROM AUTHOR]

Alloying Pt with 3d transition metals can largely promote the electrocatalytic performances of Pt-based nanocatalysts by downshifting the d-band center of Pt and modulating the electronic structure. Here, PtCo nanowire catalysts are obtained by a simple hydrothermal method. Due to the special one-dimensional (1D) nanowire structure and the strong synergistic effect between Pt and Co, the PtCo nanowire catalysts exhibit high electrocatalytic performances for ethanol oxidation reaction (EOR). The mass activity of optimal Pt1Co1 nanowires is 3.69 times of pure Pt. It also shows excellent durability and stability, which can sustain high activity after operating more than 500 cycles of electrochemical cycling. Our works point out a direction for the development of Pt-based nanomaterials with potential industrial application. [ABSTRACT FROM AUTHOR]

In the present work, an activated biocarbon (aBC) was studied as a support in Pd electrocatalyst for ethanol oxidation reaction (EOR) in alkaline medium. Pd/aBC sample was compared with a commercial Vulcan carbon supported Pd electrocatalyst. The Pd particles morphology were influenced by the high content of oxygenated surface functional groups of aBC support, which can be relevant for the synthesis of Pd based electrocatalysts, because the Pd particles formation mechanism involves the adsorption of Pd2+ on negative charged sites of aBC support. This adsorption occurs preferentially on electron donor sites such as oxygenated functional groups. Therefore, the higher concentration of these groups in aBC surface can determine a higher concentration of initial nuclei sites for Pd particles formation contributing to the particles agglomeration on aBC support, compromising the Pd/aBC electrocatalytic performance. For both prepared electrocatalysts, the spectroelectrochemical analysis demonstrates that the acetate ion is the main product of the EOR in the alkaline medium. [ABSTRACT FROM AUTHOR]

Direct ethanol fuel cells (DEFCs) are devices for clean and sustainable energy production, where the generation of electrical energy occurs as a result of the anodic ethanol oxidation reaction (EOR). One of the main challenges of these devices is the development of cost-effective and sustainable anodic catalysts, minimizing the use of noble metals such as Pd. In this sense, biomass-derived carbon-supported core–shell nanoparticles of PdNi-based electrocatalyst are of great interest for EOR and its application in DEFCs. The purpose of this work was to demonstrate the possibility of synthesizing a core–shell Ni@Pd electrocatalysts via hydrothermal method, in a fast, simple and environmental friendly way. A biomass hydrothermal liquefaction method using nickel and palladium salts was used to synthesize a biocarbon-supported nickel/palladium core–shell electrocatalyst (Ni@Pd/aHC). The electrocatalyst was morphological and chemical characterized in order to confirm the core–shell particle formation. The electrochemical characterization showed that the Ni@Pd/aHC sample has good electrocatalytic behaviour and good stability over time. The EOR mechanism on the sample and their influence in the faradaic efficiency of a cell were also studied by spectroelectrochemical analysis. [ABSTRACT FROM AUTHOR]

High-quality Pt-based catalysts are highly desirable for ethanol oxidation reaction (EOR), which is of critical importance for the commercial applications of direct ethanol fuel cells (DEFCs). However, most of the Pt-based catalysts have suffered from high cost and low operation durability. Herein a two-step method has been developed to synthesize porous Pt nanoframes decorated with Bi(OH)3, which show excellent catalytic activity and operation durability in both alkaline and acidic media. For example, the nanoframes show a mass activity of 6.87 A·mgPt−1 in alkaline media, which is 13.5-fold higher than that of commercial Pt/C. More importantly, the catalyst can be reactivated simply, which shows negligible activity loss after running for 180,000 s. Further in situ attenuated total reflection-infrared (ATR-IR) absorption spectroscopy and CO-stripping experiments indicate that surface Bi(OH)3 species can greatly facilitate the formation of adsorbed OH species and subsequently remove carbonaceous poison, resulting in a significantly enhanced stability towards EOR. This work may favor the tailoring of desired electrocatalysts with high activity and durability for future commercial application of DEFCs. [ABSTRACT FROM AUTHOR]

Nickel (oxy)hydroxides (NiOxHy) are promising cost-effective materials that exhibit a fair catalytic activity for the ethanol oxidation reaction (EOR) and could be used for sustainable energy conversion. Doping the NiOxHy structure with other metals could lead to enhanced catalytic properties but more research needs to be done to understand the role of the doping metal on the EOR. We prepared NiOxHy films doped with Fe or Co with different metallic ratios by electrodeposition and evaluated the EOR. We found a positive and negative effect on the catalytic activity after the incorporation of Co and Fe, respectively. Our results suggest that Ni atoms are the active sites for the EOR since Tafel slopes were similar on the binary and pristine nickel (oxy)hydroxides and that the formal potential of the Ni(II)/Ni(III) redox couple is a good descriptor for the EOR activity. This work also highlights the importance of controlled metal doping on catalysts and may help in the design and development of improved materials for the EOR. [ABSTRACT FROM AUTHOR]

Bimetallic Pd–Ni alloy nanoparticles with tunable dimensions, unique composition and excellent electrocatalytic activity towards methanol and ethanol oxidation reaction (MOR and EOR) in alkali, were successfully synthesized by co-reduction of metal precursors in strong alkali medium at room temperature. X-ray diffraction profiles typically signify alloy structure of the particles. Microscopy, diffraction and spectroscopy studies further conform the successful formation of Pd–Ni nanoalloy of determined diameter and morphology. The compositions of this alloy nanoparticles can be easily tuned by typically varying the Pd2+/Ni2+ molar ratio. The mol% of Ni present in the Pd–Ni bimetallic nanoalloy portrays a key role on the catalytic activity for MOR and EOR in alkali. Pd70Ni30/C catalyst exhibits the optimum synergic catalytic activity with improved oxidation of carbonaceous intermediates. Chronoamperometric study satisfactorily proves that Pd70Ni30/C is quite stable at ambient temperature and can be used as anode for MOR and EOR. [ABSTRACT FROM AUTHOR]

Bimetallic Pd/SnO2 nanoparticle electrocatalysts on metal organic framework-derived carbon (MOFDC) were successfully synthesized using microwave-assisted strategies and explored for ethanol oxidation reaction (EOR) in alkaline solution. The materials were thoroughly characterized using XRD, XPS, TEM, and Raman. TEM showed that Pd/SnO2/MOFDC gave the least average particle size of 5.5 nm compared to its counterparts on carbon black (CB). The Pd/SnO2/MOFDC gave the best electrocatalytic performance in terms of high electrochemical active surface area (ECSA) of 962 cm2 mg−1, low onset potential and overpotential for EOR, and high current density (j) of four times more than those of the Pd/CB electrocatalyst. In addition, Pd/SnO2/MOFDC showed superior kinetic parameter (in terms of the Tafel slope (b) = 216.1 ± 8 mV dec−1) and least combined resistance (R = Rs + Rct). These results show that the Pd/SnO2/MOFDPC nanoparticle electrocatalyst is promising for EOR with improved electrocatalytic properties for application in direct ethanol fuel cell (DEFC). [ABSTRACT FROM AUTHOR]

The study focuses on the influence of Ni and Bi on alkaline ethanol oxidation reaction (EOR) activities, stabilities and structure characteristics of carbon supported Pd-based nanocatalysts (Pd/C, Pd60Ni40/C, Pd60Bi40/C, Pd60Ni20Bi20/C) by cyclic voltammetry/chronoamperometry using rotating disk electrode and various physico-chemical methods such as X-ray powder diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy coupled with energy dispersive X-ray spectroscopy and inductively coupled plasma optical emission spectrometry. Nickel generates more adsorbed OH on the Pd catalyst surface than Bi and promotes the oxidation of adsorbed ethanol species. This results in a low onset potential toward ethanol oxidation with high current density. The presence of Bi facilitates high tolerance toward various reaction intermediates resulting from the incomplete ethanol oxidation, but might also initiate the agglomeration of Pd nanoparticles. The novel Pd60Ni20Bi20/C nanocatalyst displays exceptional byproduct tolerance, but only satisfying catalytic activity toward ethanol oxidation in an alkaline medium. Therefore, the EOR performance of the novel carbon supported ternary PdxNiyBiz anode catalyst with various atomic variations (Pd70Ni25Bi5/C, Pd70Ni20Bi10/C, Pd80Ni10Bi10/C and Pd40Ni20Bi40/C) using the common instant reduction synthesis method was further optimized for the alkaline direct ethanol fuel cell. The carbon supported Pd:Ni:Bi nanocatalyst with atomic ratio of 70:20:10 displays outstanding catalytic activity for the alkaline EOR compared to the other PdxNiyBiz/C nanocatalysts as well as to the benchmarks Pd/C, Pd60Ni40/C and Pd60Bi40/C. The synergy and the optimal content in consideration of the oxide species of Pd, Ni and Bi are crucial for the EOR kinetic enhancement in alkaline medium. [ABSTRACT FROM AUTHOR]

The development of Pt-based core/shell nanoparticles represents an emerging class of electrocatalysts for fuel cells, such as methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). Here, we present a one-pot synthesis approach to prepare hexagonal PtBi/Pt core/shell nanostructure composed of an intermetallic Pt1Bi1 core and an ultrathin Pt shell with well-defined shape, size, and composition. The structure and the synergistic effect among different components enhanced their MOR and EOR performance. The optimized Pt2Bi nanoplates exhibit excellent mass activities in both MOR (4,820 mA·mgPt -1) and EOR (5,950 mA·mgPt-1) conducted in alkaline media, which are 6.15 times and 8.63 times higher than those of commercial Pt/C, respectively. Pt2Bi nanoplates also show superior operation durability to commercial Pt/C. This work may inspire the rational design and synthesis of Pt-based nanoparticles with improved performance for fuel cells and other applications. [ABSTRACT FROM AUTHOR]

Rare earths (RE) have been studied in the literature as additives in Pt and PtSn catalysts for the ethanol oxidation reaction (EOR), but their stability and influence on the mechanism of the EOR have not been reported. In this work, PtSnRE/C (RE: La, Ce, and Pr) catalysts were obtained by the polyol method, characterized, and their stability toward the EOR evaluated by cycling at two different potential ranges. The accelerated aging tests indicated that despite the changes in the CO stripping profiles, the ternary catalysts exhibit higher current densities after aging than Pt/C and PtSn/C catalysts. Even after dissolution of the rare-earth metals, as observed by energy-dispersive X-ray spectroscopy (EDS) before and after aging, the EOR activity after short-term stability tests was found to be higher than the initial one. The addition of these metals facilitates the retention of tin in the material, contributing to the overall stability of the bimetallic catalyst. The oxidation products of the ternary catalysts were evaluated by in situ Fourier transform infrared spectroscopy (FTIR) spectroscopy and high-performance liquid chromatography (HPLC), where the major products were found to be acetaldehyde and acetic acid, with only small concentrations of CO2. The improvement in the ethanol oxidation efficiency by PtSnRE/C catalysts can be explained by a bifunctional mechanism in which the rare-earth oxides are able to provide oxygenated species at low potentials. [ABSTRACT FROM AUTHOR]

Although nanostructures based on noble metal alloys are widely utilized in (electro)catalysis, their low-temperature synthesis remains an enormous challenge due to the different Nernst equilibrium potentials of metal precursors. Herein, we describe the successful synthesis of trimetallic PtRhNi alloy nanoassemblies (PtRhNi-ANAs) with tunable Pt/Rh ratios using a simple mixed cyanogel reduction method and provide a detailed characterization of their chemical composition, morphology, and structure. Additionally, the electrochemical properties of PtRhNi-ANAs are examined by cyclic voltammetry, revealing composition-dependent electrocatalytic activity in the ethanol oxidation reaction (EOR). Compared to a commercial Pt black electrocatalyst, optimized PtRhNi-ANAs display remarkably enhanced EOR electrocatalytic performance in alkaline media. [ABSTRACT FROM AUTHOR]

Carbon-supported oxide-rich Pd-W bimetallic nanoparticles were prepared by chemical reduction methods. The existence of oxides in the electrocatalysts is confirmed by X-ray photoelectron spectrum (XPS) and high resolution transmission electron microscopy. XPS analysis indicates that the oxygen atoms account for about 50% of all the atoms in Pd-W bimetallic nanoparticles. Compared to Pd/C catalyst, the carbon-supported oxide-rich Pd-W bimetallic nanoparticles exhibit a better catalytic activity for the anode oxidation of ethanol in alkaline media. The onset potential of the as prepared oxide-rich PdW/C catalyst (Pd: W = 8: 2, metal atom ratio) for ethanol oxidation is negative shifted about 90 mV comparing to Pd/C catalyst. The oxide-rich Pd-W/C electrocatalysts provide a new model of noble-metal/promoter system as an extreme case of making the promoter (WO) closely adjacent to the noble metal (Pd) by fabricating nanoparticles containing both atom-clusters of oxides and the noble metal atoms. [ABSTRACT FROM AUTHOR]

The development of advanced materials is a central issue to accelerate the implementation of fuel cell technology which constitutes immense potential to meet future power sources. In this work, a facile, one-pot synthesis of Pd nanoparticles (NPs)/polypyrrole (PPy) nanofiber composites has been reported using oxidative complexes as soft templates. Average size of Pd NPs within the PPy nanofibers was found to be in the range of 2.2-4 nm as measured from transmission electron microscopic (TEM) image. The NPs possess good degree of crystallinity as discernible from the lattice fringes in high-resolution transmission electron microscopy (HRTEM), and the cubic crystal phase was ascertained from the X-ray diffraction (XRD) pattern. Electrochemical measurements like cyclic voltammetry (CV) and chronoamperometry (CA) measurements demonstrate that the Pd NP-based polymer nanocomposites (PNCs) show superior electrocatalytic activity for ethanol oxidation and higher stability compared to the commercial Pd/C catalysts which suggest the significant advantages of polymer support over carbon support. The enhanced electrochemical performance attributed with low charge-transfer resistance of the composite catalyst facilitates an easier access of ethanol molecules to the catalytic sites. The mass activity of Pd/PPy nanocomposites is 7.5 and 78 times higher than that of commercial Pd/C and bulk Pd/PPy composites. The effective dispersion of the Pd NPs within the conducting polymer nanostructures allowed an enhancement of the catalytic activity. Our adopted method could be suitable for further development of advanced anode catalyst for alkaline fuel cell applications. [ABSTRACT FROM AUTHOR]

The present paper reports on a significant enhancement of ethanol oxidation reaction (EOR), investigated on Pt and PtSn-modified nickel foam electrodes, realized via in situ formation of surface nickel oxy-hydroxide layer in 0.1 M NaOH solution. In the presence of ethanol in electrolyte, adsorbed CHOH molecules (and/or its oxidation intermediates) prevent Pt (PtSn) sites from their extensive dissolution upon prolonged surface electrooxidation of Ni foam electrode. The above was elucidated through cyclic voltammetry examinations and a.c. impedance-derived charge transfer resistance parameter values. Surface topography and the presence of catalytic additives were revealed from the combined scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) analyses. [ABSTRACT FROM AUTHOR]

The search for new catalyst support matrices to replace the conventional carbon black support has been an important research field for decades. Aromatic conducting polymer (ACP)-based matrices have been found as prospective candidates. Poly(amic) acid (PAA) is one such polymer. We hereby present the catalytic activity and stability of electrodeposited palladium (PdNPs) and platinum (PtNPs) nanoparticles stabilized with PAA. We fabricated four electrodes: Pd/GCE, PAA/Pd/GCE, Pt/GCE, and PAA/Pt/GCE. Cyclic voltammetry and chronoamperometry were employed to assess the ethanol oxidation reaction using PAA as support matrix. PAA was used as support to enhance the stability of PdNPs and PtNPs in basic and acidic media, respectively. The synthesized PAA was characterized using NMR and FTIR. Scanning electron microscopy and X-ray diffraction (XRD) were used for nanoparticle characterization. Test results revealed that the presence of PAA layer on the catalysts leads to sluggish electron transfer kinetics as deduced from higher forward and reverse current densities (5 and 11 mA/cm) for PdNPs on glassy carbon (Pd/GCE) electrode compared to PAA-stabilized PdNPs (PAA/Pd/GCE) (0.6 and 1.2 mA/cm), respectively. A similar trend was reported for PtNPs. However, in presence of PAA, both PtNPs and PdNPs were observed to provide stability at up to 900 and 150 cycles, respectively. Chronoamperometric results reinforced the catalyst stabilization effect of the polymer, with findings revealing that the steady-state current density of PAA/Pd/GCE was ∼2.5 times higher than the bare Pd/GCE. [ABSTRACT FROM AUTHOR]

The present paper reports on ethanol oxidation reaction (EOR) investigated at catalytically modified nickel foam material. The EOR was studied in 0.1 M NaOH supporting electrolyte on Pd-activated nickel foam catalyst material, obtained by a spontaneous deposition method. Catalytic modification of Ni foam resulted in a composite material having superior EOR kinetics, as elucidated through corresponding values of a.c. impedance-derived charge-transfer resistance parameter (including temperature-dependence of the EOR over the temperature range 20-60 °C). The presence of a catalytic additive was disclosed from SEM and XRD analyses. [ABSTRACT FROM AUTHOR]

Composite microparticles consisting of large gold (Au) particles embedded with multi-walled carbon nanotubes (MWCNTs), denoted as MWCNTs-Au, have been successfully prepared by a facile hydrothermal process of gold(III) chloride (AuCl) in a MWCNT aqueous solution. X-ray diffraction and scanning electron microscopy reveal that the obtained Au particles have an average diameter of about 500 nm and some MWCNTs are inserted into the Au particles. The MWCNTs-Au composites in the ethanol oxidation reaction (EOR) show quite different shape of cyclic voltammograms (CVs) toward EOR when compared to the previous CV reports on the pure Au substrate. [ABSTRACT FROM AUTHOR]

Carbon-supported ternary Pt-Rh-SnO electrocatalysts with two different stoichiometries (i.e. PtRhSn/C and PtRhSn/C) were synthesized using a two-step sequential approach. Characterization of the catalysts was conducted by a range of techniques. X-ray diffraction (XRD), together with high resolution transmission electron microscope (HR-TEM) studies showed that the obtained electrocatalysts were composed of two categories of nanoparticles: PtRh solid solution and SnO. Electrochemical measurements showed that both ternary catalysts demonstrated superior performance over the conventional Pt/C and PtRu/C catalysts for ethanol electrooxidation reaction (EOR). Between the two catalysts, the one having lower SnO content (i.e. PtRhSn/C) exhibited the higher activity and greater stability. In situ X-ray absorption spectroscopy (XAS) studies revealed structural information of the nanocatalysts, including bond distances, coordination numbers, and stoichiometry consistent with independently obtained inductively coupled plasma-optical emission spectroscopy (ICP-OES) data. The results suggested that a metal-metal oxide interaction in the ternary Pt-Rh-SnO system with higher oxide (i.e. SnO) content has caused the increase in oxidation state of both Pt and Rh, which may explain the lower activity of the catalyst for EOR. [ABSTRACT FROM AUTHOR]

This work presents an 'in situ' spectroelectrochemical study of the ethanol oxidation reaction on Pt/C electrocatalysts prepared by the polymeric precursor method. Characterization of the electrocatalysts was performed with X-ray diffraction, Raman spectroscopy, and cyclic voltammetry measurements. The average crystallite size was estimated as 7 nm, in agreement with the value reported in the literature for these types of electrocatalysts. The cyclic voltammetry characterization in an acidic medium presented the expected voltammetric behavior for polycrystalline Pt/C. The ethanol oxidation process was successfully employed 'in situ', making use of an optical probe for excitation and collection of the Raman scattering signal. In this configuration it was possible to track the formation of the main products-CO, CO indirectly, acetaldehyde, and acetic acid-and to measure the decay of the ethanol concentration. The results indicate that the optical probe-based Raman spectroscopy technique is a very effective tool for studying 'in situ' electrochemical oxidation reactions of ethanol. It might also be a very promising characterization technique for studies of the 'in situ' electrochemical oxidation of small organic molecules. [ABSTRACT FROM AUTHOR]

Direct ethanol fuel cells (DEFCs) are a promising carbon-neutral and sustainable power source for portable, mobile, and stationary applications. However, conventional DEFCs that use acid proton-exchange membranes (typically Nafion type) and platinum-based catalysts exhibit low performance (i.e., the state-of-the-art peak power density is 79.5 mW/cm at 90°C). Anionexchange membrane (AEM) DEFCs that use low-cost AEM and non-platinum catalysts have recently been demonstrated to yield a much better performance (i.e., the state-of-the-art peak power density is 160 mW/cm at 80°C). This paper provides a comprehensive review of past research on the development of AEM DEFCs, including the aspects of catalysts, AEMs, and single-cell design and performance. Current and future research challenges are identified along with potential strategies to overcome them. [ABSTRACT FROM AUTHOR]