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The natural scarcity and insufficient utilization of noble metal-based catalysts bring a heavy block in the way of the widespread applications of direct methanol fuel cells. Herein, we propose a feasible bottom-up approach to the construction of ultrasmall Pd nanocrystals confined into Co-based metal organic framework-decorated Ti 3 C 2 T x MXene (Pd/MOF-MX) nanoarchitectures via a controllable solvothermal process. The ultrathin MXene nanolamellas and porous Co-based MOFs constitute an ideal hybrid carrier with high electron conductivity and large accessible surface areas, which not only facilitates the size restriction and uniform dispersion of Pd nanocrystals, but also ameliorates their intrinsic catalytic activity through the direct electronic interactions. By virtue of the pronounced synergistic coupling effects, the newly-developed Pd/MOF-MX nanoarchitectures exhibit markedly enhanced electrocatalytic properties towards the methanol oxidation reaction, including a large electrochemically active surface area of 116.7 m2 g−1, a high mass activity of 1700.4 mA mg−1 as well as a satisfactory long-term durability, which are superior to those of traditional Pd electrocatalysts anchored on carbon blacks, carbon nanotubes, graphene, and undecorated MXene matrixes. A feasible bottom-up approach is developed to the stereo-formation of ultrasmall Pd nanocrystals confined into Co-MOF-decorated Ti 3 C 2 T x MXene nanoarchitectures via a controllable solvothermal process, which exhibit superior electrocatalytic performance for methanol electrooxidation. [Display omitted] • The bottom-up construction of Co-based MOF-decorated MXene matrix is achieved. • Ultrasmall Pd nanocrystals are uniformly confined into the MOF-MXene frameworks. • The MOF-MXene matrix affords strong electronic interactions with Pd component. • The optimized nanoarchitecture shows exceptional methanol oxidation performance. [ABSTRACT FROM AUTHOR]

Advancements in microreactor technology emerge as a promising solution for low-cost hydrogen (H 2) production, and there is significant progress being made towards developing microreactor technology for onboard H 2 production. It is possible that fully matured microreactor technology for onboard H 2 production will become available in the next decade. This review summarizes the key numerical findings in the advancements of research on H 2 production by steam reforming in microreactors. Although numerous studies are being conducted on microreactors for different fuels, flow altering structures, and reaction parameters for steam reforming, they still lag in considering all parameters. This study aims to comprehend all performance influencing parameters, both structural and reaction, to better understand the selection of a microreactor. Based on the findings of this study, it is recommended to use methanol as the fuel and an optimal design that is easy to fabricate while also offering high performance. Since performance is influenced by numerous parameters, identifying the best conditions for the reaction and optimal structure can be achieved through the use of artificial intelligence (AI) techniques. [Display omitted] • Microreactor coupled to fuel cells for onboard applications. • Comprehensive review of studies on hydrogen production in microreactors. • CO free hydrogen can be produced from methanol steam reforming in microreactor. • Structural parameters have the most influence on microreactor performance. • AI can enhance microreactor performance by optimizing various parameters. [ABSTRACT FROM AUTHOR]

Recent advancements in microfluidics enable the production of hydrogen (H 2) through microreactors, resulting in enhanced safety, reaction control, and superior performance. This technology shows potential for addressing issues related to current H 2 production systems. The present review article focuses on the latest developments in microreactor technology for H 2 production, including an in-depth examination of various aspects such as reaction mechanisms for different fuels, diverse techniques utilized for microreactor fabrication, catalyst coating, performance evaluation, and microchannel arrangement. This study emphasizes the significance of selecting optimal parameters to achieve high microreactor performance, with structural and reaction conditions being the most influential factors based on a comprehensive analysis of experimental studies. This review article explores energy sources, materials, and catalysts for microreactor technology, contributing to its development for enhanced H 2 production. Recent advancements include flexible microreactors, renewable energy utilization, utilization of advanced fabrication techniques, and new materials to overcome challenges and improve performance. [Display omitted] • Microreactors produce clean hydrogen from feed reactants. • Fuel choice is critical for microreactor reforming and fuel cell coupling. • Efficient hydrogen production is achieved with various microreactor structures. • Ceramic materials offer chemical stability and excellent corrosion resistance. • Feed flux and S/C ratio impact microreactor performance significantly. [ABSTRACT FROM AUTHOR]

Monitoring the methanol concentration is critical for direct methanol fuel cell (DMFC) reliability. However, monitoring the concentration is expensive due to the high cost of concentration sensors. This paper describes an advanced sensor-less method for monitoring methanol concentration during the rest cycle of a DMFC using the voltage decay rate (k v t ). Based on the dynamic behavior of methanol mass transfer and reaction in DMFC during the rest cycle, a feedback equation for methanol concentration is constructed in this method. The rationality of the feedback equation is then confirmed through a series of sensitivity analysis experiments at various methanol concentrations, cell temperatures, and load currents. In addition, 1,900 experiments under random conditions simulating practical applications are used to assess the accuracy of the feedback equation. According to the results, 89.6% of the 1,900 experiments have concentration prediction errors of less than 0.05 mol L−1. The mean error and standard deviation of error are found to be 0.005 mol L−1 and 0.031 mol L−1, respectively. These findings point to the desired accuracy and stability of the sensor-less method, as well as promising applications in a variety of scenarios. • A precise 2D DMFC model was built with only 4.5% error for IV polarization curves. • A concise quadratic concentration feedback equation was derived based on the model. • The concentration feedback equation was validated by 1900 random experiments. • The concentration feedback equation achieves prediction errors below 0.05 mol L−1. [ABSTRACT FROM AUTHOR]

Abstract This research investigates the structure and characteristics of microwave-assisted graphene oxide (denoted as MGO) nanofillers and their effect as membrane electrolyte assembly for direct alkaline methanol fuel cell (DAMFC). Two types of GO nanosheets are fabricated: MGO and modified Hummer's method (denoted as NGO). The MGO contained less oxygen (i.e. higher C/O ratio) and higher D/G band ratio than NGO, indicating the microwave method yielded less hydrophilic GO with more sp3 C-C bonds than NGO sample. The shorter reaction time (20 min) of the microwave method also generated larger GO sizes than the conventional method. The MGO contained less ether groups and more resistant to thermal degradation than NGO. One percent GO nanofillers are incorporated into polybenzimidazole (PBI) to form composite membranes, which are subsequently doped with KOH. The PBI/NGO had the highest conductivity while the PBI/MGO had the lowest permeability among the three membranes. DAMFC equipped with PBI/NGO and PBI/MGO electrolytes resulted in peak power densities of 310 and 277 mW cm−2 at 80 °C, respectively. These demonstrated power densities are significantly higher than those reported in literature. Considering the short time and facile method for MGO synthetic process, this microwave-assisted GO has potential as fillers into composite membranes. Highlights • Microwave assisted GO (MGO) and that from modified Hummer's (NGO) are synthesized. • MGO contains less oxygen and higher D/G band ratio than the NGO sample. • PBI incorporated with GO fillers are produced for alkaline fuel cell electrolyte. • PBI/MGO shows lower alcohol permeability and PBI/NGO has higher ionic conductivity. • P max of PBI/MGO and PBI/NGO films are 277 and 310 mW cm−2, respectively, at 80 °C. [ABSTRACT FROM AUTHOR]

Abstract Self-support silver nanofibers with excellent electrocatalytic performance for oxygen reduction reaction (ORR) are successfully fabricated through a hybrid method combining an electrospinning process with an electroplating technique. This nanofiber-based catalyst demonstrated superior long-term stability and an unusually high methanol-tolerant effect that its ORR activity was enhanced, instead of lessened in 3 M methanol. The impact of microstructure and crystal facet on ORR activity is examined through quantifying the performance of the catalysts by electrochemical measurements. Through tuning the synthesis parameters, the onset potential, half-wave potential, and peak potential of 1.041 V, 0.848 V, and 0.864 V are achieved for the silver nanofibers with thorny structure, even superior to those of commercial Pt/C catalyst. Such excellent performance is attributed to two major factors, the micro morphology, i.e. thorn-on-fiber structure, and the crystal facet. The special thorny structure leads to the accumulation of electrons on the tip to act as highly active sites and better confinement of the oxygen between thorns, while the high ratio of (110) facets on the tip favors high catalytic activity. This kind of low-cost silver nanofiber-based catalyst exhibits a highly beneficial prospect as a potential alternative catalyst for oxygen reduction reaction. Graphical abstract Image 1 Highlights • Supportless AgNFs with thorny structures were synthesized. • The best ORR activity among the reported Ag-based catalysts. • Superior long-term stability and an unusual methanol response. • Electron enrichment and high (110) facet exposure appear at thorny tips. • Their synergetic roles greatly contribute to high ORR activity. [ABSTRACT FROM AUTHOR]

Abstract Methanol is a volatile fuel which can be fed into microfluidic fuel cells in vaporized form. However, the methanol oxidation reaction is relatively sluggish compared with the hydrogen oxidation reaction. Therefore, a novel dual fuel microfluidic fuel cell system powered by both methanol and methanol-derived hydrogen via photocatalysis is developed, which can achieve much improved cell performance while eliminating the hydrogen transportation, storage and safety issues. Pt/P25 is adopted as the photocatalyst which photo-reforms the methanol to hydrogen in the fuel tank. The intermediate during the photoreforming process can also be fed into the microfluidic fuel cell as a fuel. Different cell performance can be achieved by varying the fuel-water mix ratios in the tank. By optimizing the ratio, the peak power density can be increased by more than 10 times when the system is exposed to simulated solar light (3 suns) illumination. Highlights • A dual fuel system of methanol and hydrogen for MFC was demonstrated. • Hydrogen generated from methanol solution via photocatalysis with Pt/P25. • Mixed potential of hydrogen and methanol was studied. • MFC power output increased by more than 10 times when solar light was available. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates potentials of a porous silicon aluminum oxide particles obtained by heating NH 4 -X zeolite powder as an innovative filler to form composite Nafion membranes for direct methanol fuel cells. Results from XRD show the filler has an amorphous type structure whereas FTIR, BET and 27Al MAS-NMR analysis show zeolite-like cage structures still exist. The Nafion composite membranes are prepared by solvent casting with filler content equal to 1.25 wt%, 2.5 wt%, 3.75 wt% and 5 wt%, respectively. The composite membranes show performance promotion in water uptake, ion exchange capacity, proton conductivity and methanol permeability in comparison to pristine Nafion due to the synergistic effect of Nafion, Si OH and Si O SO 3 H groups, skeleton framework, and porous structure of the activated filler. Especially, the membrane with 3.75 wt% filler shows the highest selectivity and excellent performance in terms of peak power density. For example at 80 °C, it exhibits a peak power density of 217 mW cm−2 which is more than 4 times the value of the pristine Nafion membranes prepared in this work. Highlights • Porous silicon aluminum oxide (PSAO) was prepared by heating NH 4 -X zeolite. • The Nafion membranes composited with PSAO were prepared by recasting method. • PSAO can effectively enhance proton conductivity and restrain methanol penetration. • Highest selectivity was achieved for the membranes with 3.75 wt% PSAO. • The peak power density is more than 4 times than that of pure Nafion at 80 °C. [ABSTRACT FROM AUTHOR]

Abstract The Palladium/polydopamine (Pd/PDA) litchi-like nanoclusters are synthesized via a two-step route. The resultant product is characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and the electrochemical properties were evaluated by cyclic voltammetry (CV) and chronoamperometry. Notably, the as-prepared litchi-like Pd/PDA nanoclusters show superior catalytic properties for methanol electro-oxidation in an alkaline medium due to unique Pd dots adhered at PDA surface providing a large electrochemically active surface area (ECSA). Additionally, the high concentration of oxygen functional groups on PDA is essential to the removal of carbonaceous species from the adjacent at the Pd sites. This PDA-based straightforward synthesis strategy offers a new pathway for developing highly active electrocatalysts with aid of special organic polymer. Graphical abstract Image 1 Highlights • Well dispersive litchi-like Pd nanoclusters is made using optimal amount of polydopamine. • Such Pd@PDA with many exposure active sites has superior catalysis for methane oxidation. • Pd@PDA existing many OH groups shows a good capability against CO species poison. [ABSTRACT FROM AUTHOR]

For the first time, tavorite-structured LiFeSO 4 F is synthesized using supercritical methanol at 300 °C within a short reaction time of 15 min. The synthesis involves topotactic insertion of LiF in the supercritical solution into szomolnokite-type FeSO 4 ⋅H 2 O, whose structure is similar to that of the tavorite. The introduction of the co-solvent, tetraethylene glycol, solubilizes LiF partially and significantly promotes the incorporation of LiF into the structure, enabling the synthesis of highly uniform granular particles of the tavorite sized approximately 200 nm, in 15 min. The longer reaction time in supercritical methanol at 300 °C results in reduced reversible Li storage capacity and inferior cycling stability. Furthermore, the increase in the synthesis temperature results in a phase transition to triplite LiFeSO 4 F, which is a more thermodynamically stable phase in the synthetic temperature ranges considered. This study provides a new insight into the facile synthesis of other related fluorosulfate or fluorophosphate materials using supercritical methanol. [ABSTRACT FROM AUTHOR]

Transition to renewable energy systems is essential to achieve the climate change mitigation targets. However, the timing and the regions of the production and consumption of the renewable energy do not always match, and different energy storage technologies are needed to secure the uninterrupted energy supply. Liquid organic hydrogen carriers (LOHCs) offer a flexible media for the storage and transportation of renewable energy. These “liquid hydrogen batteries” are reversibly hydrogenated and dehydrogenated using catalysts at elevated temperatures. Commercial LOHC concepts are already available. Another flexible route to store energy is through “circular” hydrogen carriers, such as methanol and methane produced from atmospheric carbon dioxide (CO 2 ). These fuels have a long history as fossil fuels. In this review, the chemistry and state-of-the-art of LOHCs are explored and discussed against defined criteria with comparison made to existing energy storage systems. The LOHCs and “circular” hydrogen carriers were found to be particularly promising hydrogen storage systems. [ABSTRACT FROM AUTHOR]

Steam reforming of diesel is performed over Ru/γ-Al 2 O 3 and Ni/γ-Al 2 O 3 catalysts. The catalysts both achieve 100% diesel conversion rate and high hydrogen selectivity at temperatures over 600 °C but Ni/γ-Al 2 O 3 catalyst shows a poor carbon tolerance, carbon deposition has been detected after 10 h of test which is determined as encapsulating carbon. Co-reforming diesel and methanol is conducted by adding methanol into the steam-diesel mixture as a stabilizer and it successfully extends the long-term life from 120 h to 600 h at 750 °C. The reformed diesel gas (RDG) is then fed into a solid oxide fuel cell (SOFC) to investigate fuel adaptability. The cell has achieved a peak power density of 1.34 W/cm2 at 750 °C under RDG fuel, and the cell voltage has stabilized at 0.82 V for 200 h during the galvanostatic discharge of 0.4 A/cm2. No detectable carbon deposition has occurred on the surface of the Ni-YSZ anode. The results demonstrate that the reformed diesel gas provides a good fuel choice for solid oxide fuel cell application. • 100% conversion diesel was achieved at temperatures higher than 600 °C. • Carbon deposition on catalyst was determined to be encapsulating type. • Long-term life test was extended from 120 h to 600 h after methanol was added. • Integrated diesel-fueled SOFC achieved 1.34 W/cm2 and 200 h stable discharge. [ABSTRACT FROM AUTHOR]

Direct methanol fuel cells (DMFCs) are promising electrochemical systems capable of producing electricity from the electrochemical oxidation of methanol and the reduction of oxygen. In this work, the effectiveness of the addition of sulfuric acid as a supporting electrolyte for methanol fuel composition was assessed. The results showed that the peak of power curve in DMFCs with Pt/C cathode electrocatalysts increased progressively from 70 mW cm−2 (0 mM of H 2 SO 4) to 115 mW cm−2 with a concentration of 100 mM of H 2 SO 4. These results underlined the positive effect of the addition of a supporting electrolyte in the methanol aqueous solution on the electrochemical output that was enhanced. Platinum group metal-free (PGM-free) electrocatalysts based on Fe-N x -C type were also tested being insensitive to methanol crossover and oxidation at the cathode. DMFC with Fe–N–C cathode catalysts result in a performance of 21.5 mW cm−2. In these operating conditions, the addition of supporting electrolyte does not seem to bring excessive advantage. Short stability tests are presented and an overall assessment of the resistances within the system is also discussed. • Addition of H 2 SO 4 in methanol feed boosts DMFC power density using Pt/C catalyst. • Power density is not dependent on H 2 SO 4 concentration using PGM-free catalyst for ORR. • Addition of H 2 SO 4 does not affect short-term cell performance. • Catalysts morphology and composition are not affected by H 2 SO 4 presence. [ABSTRACT FROM AUTHOR]

In this study, a novel reactor model is developed by combining protonic ceramic electrolyzer cell (PCEC) electrolysis for hydrogen production and CO 2 recycling for methanol synthesis. The problem of temperature mismatch between PCEC and methanol synthesis is solved by supplying low-temperature gas intermediately, so as to realize the integrated direct synthesis of methanol. After model validation, a study of the effects of key operating parameters on the methanol production and temperature distribution of the system is conducted. It is found that increasing the operating voltage and electrolysis operating temperature, or decreasing the supplemental gas temperature enhances methanol production, while the carrier gas flow rate, supplemental gas flow rate and anode flow rate all have the optimal values (Q N2 = 10–35 SCCM, Q CO2 = 20–50 SCCM and Q an = 250–300 SCCM). Meanwhile, the temperature distribution of the system is also significantly affected by the above operating parameters, and it is possible to achieve a precise control of the operating conditions of the coupled system by adjusting the above operating parameters to ensure an efficient and long-term operation. This study provides an insight and a new approach for the recycling of CO 2 and the green synthesis of methanol. • A 2D numerical model is developed for PCEC electrolysis and methanol synthesis. • A novel approach of supplying low-temperature gas intermediately is adopted. • The effects of different key operating parameters are studied and analyzed. • The temperature field of the coupled system is investigated. [ABSTRACT FROM AUTHOR]

In the membraneless direct methanol redox fuel cell (DMRFC), three-dimensional electrodes contribute to the reduction of methanol crossover and the open separator design lowers the system cost and extends its service life. In order to better understand the mechanisms of this configuration and further optimize its performance, the development of a three-dimensional numerical model is reported in this work. The governing equations of the multi-physics field are solved based on computational fluid dynamics methodology, and the influence of the CO 2 gas is taken into consideration through the effective diffusivities. The numerical results are in good agreement with experimental data, and the deviation observed for cases of large current density may be related to the single-phase assumption made. The three-dimensional electrode is found to be effective in controlling methanol crossover in its multi-layer structure, while it also increases the flow resistance for the discharging products. It is found that the current density distribution is affected by both the electronic conductivity and the concentration of reactants, and the temperature rise can be primarily attributed to the current density distribution. The sensitivity and reliability of the model are analyzed through the investigation of the effects of cell parameters, including porosity values of gas diffusion layers and catalyst layers, methanol concentration and CO 2 volume fraction, on the polarization characteristics. [ABSTRACT FROM AUTHOR]

Sulfonated polymer/graphene oxide (GO) nanocomposites exhibit excellent properties as proton exchange membranes. However, few investigations on highly branched sulfonated poly(arylene ether)s (HBSPE)/GO nanocomposites as proton exchange membranes are reported. In order to obtain HBSPE-based nanocomposite membranes with better dispersibility and properties, a novel GO containing flexible alkylsulfonated side chains (SGO) is designed and prepared for the first time in this work. The HBSPE/SGO nanocomposite membranes with excellent dispersibility are successfully prepared. The properties of these membranes, including the mechanical properties, ion-exchange capacity, water uptake, proton conductivity, and methanol resistance, are characterized. The nanocomposite membranes exhibit higher tensile strength (32.67 MPa), higher proton conductivity (0.39 S cm −1 at 80 °C) and lower methanol permeability (4.89 × 10 −7  cm 2  s −1 ) than the pristine membrane. The nanocomposite membranes also achieve a higher maximum power density (82.36 mW cm −2 ) than the pristine membrane (67.85 mW cm −2 ) in single-cell direct methanol fuel cell (DMFC) tests, demonstrating their considerable potential for applications in DMFCs. [ABSTRACT FROM AUTHOR]

Meta- and para-linked homopolymers bearing 3-methylphenyl (Me) pendent groups were postsulfonated to create sulfonated poly(ether ether ketone ketone) (SPEEKK) backbone isomers, which are referred to as Me- p -SPEEKK and Me- m -SPEEKK. Their thermal and oxidative stability, mechanical properties, dimensional stability, methanol permeability, and proton conductivity are characterized. Me- p -SPEEKK and Me- m -SPEEKK proton conductivities at 100 °C are 116 and 173 mS cm −1 , respectively. Their methanol permeabilities are 3.3–3.9 × 10 −7 cm 2 s −1 , and dimensional swelling at 100 °C is 16.4–17.5%. Me- p -SPEEKK and Me- m -SPEEKK were fabricated into membrane electrode assemblies (MEAs), and electrochemical properties were evaluated within a direct methanol fuel cell (DMFC) and proton-exchange membrane fuel cell (PEMFC). When O 2 is used as the oxidant at 80 °C and 100% RH, the maximum power density of Me- m -SPEEKK reaches 657 mW cm −2 , which is higher than those of Nafion 115 (552 mW cm −2 ). DMFC performance is 85 mW cm −2 at 80 °C with 2.0 M methanol using Me- p -SPEEKK due to its low MeOH crossover. In general, these electrochemical results are comparable to Nafion. These ionomer properties, combined with a potentially less expensive and scalable polymer manufacturing process, may broaden their potential for many practical applications. [ABSTRACT FROM AUTHOR]

The primary goal of this study is to develop a high-performanced proton exchange membrane with the characteristics of through-membrane and continuous solution blown nanofibers as proton-conducting channels. The curled sulfonated phenolphthalein poly (ether sulfone) and poly (vinylidene fluoride) nanofibers were separately fabricated through the solution blowing process which is a new nanofiber fabricating method with high productivity, then they were fabricated into a sandwich-structured mat. Then this sandwich-structured mat was hot-pressed to form the designed structure using different melting temperatures of the two polymers by melting and making poly (vinylidene fluoride) flow into the phenolphthalein poly (ether sulfone) nanofiber mat. The characteristics of the composite membrane, such as morphology and performance of the membrane, were investigated. The characterization results proved the successful preparation of the membrane structure. Performance results showed that the novel structured membrane with through-membrane nanofibers significantly improved water swelling and methanol permeability, though its conductivity is lower than that of Nafion, the cell performance showed comparable results. Therefore, the novel structure design can be considered as a promising method for preparing of proton exchange membranes. [ABSTRACT FROM AUTHOR]

Effects of supports over Pt/In 2 O 3 /MO x catalysts with extremely low loading of Pt (1 wt%) and In 2 O 3 loadings (3 wt%) are investigated for the hydrogen production of methanol steam reforming (MSR) in the temperature range of 250–400 °C. Under practical conditions without the pre-reduction, the 1Pt/3In 2 O 3 /CeO 2 catalyst shows the highly efficient catalytic performance, achieving almost complete methanol conversion (98.7%) and very low CO selectivity of 2.6% at 325 °C. The supported Pt/In 2 O 3 catalysts are characterized by means of Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), high-resolution transmission microscopy (HRTEM), temperature programmed reduction with hydrogen (H 2 -TPR), CO pulse chemisorption, temperature programmed desorption of methanol and water (CH 3 OH-TPD and H 2 O-TPD). These demonstrate that the nature of catalyst support of Pt/In 2 O 3 /MO x plays crucial roles in the Pt dispersion associated by the strong interaction among Pt, In 2 O 3 and supporting materials and the surface redox properties at low temperature, and thus affects their capability to activate the reactants and determines the catalytic activity of methanol steam reforming. The superior 1Pt/3In 2 O 3 /CeO 2 catalyst, exhibiting a remarkable reactivity and stability for 32 h on stream, demonstrates its potential for efficient hydrogen production of methanol steam reforming in mobile and de-centralized H 2 -fueled PEMFC systems. [ABSTRACT FROM AUTHOR]

Modeling and CFD simulation of a three-dimensional microreactor includes thirteen structured parallel channels is performed to study the hydrogen production via methanol steam reforming reaction over a Cu/ZnO/Al 2 O 3 catalyst. The well-known Langmuir-Hinshelwood macro kinetic rate expressions reported by Peppley and coworkers [49] are considered to model the methanol steam reforming reactions. The effects of inlet steam to methanol ratio, pre-heat temperature, channels geometry and size, and the level of external heat flux on the hydrogen quality and quantity (i.e., hydrogen flow rate and CO concentration) are investigated. Moreover, the possibility of reducing the CO concentration by passing the reactor effluent through a water gas shift channel placed in series with the methanol reformer is studied. Afterwards, the simulation results are compared with the experimental data reported in the literature considering two different approaches of mixture-averaged and Maxwell-Stefan formulations to evaluate the diffusive flux of mass. The results indicate that the predictions of the Maxwell-Stefan model is in better agreement with experimental data than mixture-averaged one, especially at the lower feed flow rates. [ABSTRACT FROM AUTHOR]

The state-of-the-art Ni/yttria-stabilized zirconia (YSZ) anodes in direct methanol solid oxide fuel cells (SOFCs) are vulnerable to carbon deposition. We propose two strategies to enhance coking tolerance of the cell, focusing on promoting the oxygen storage capacity of the Ni/YSZ anode and the methanol conversion in flat-tube SOFCs with an active area of 60 cm2. The Ni/YSZ anodes are decorated with nanosized gadolinia-doped ceria (GDC) by wet impregnation method and the fuel channels are filled with extra GDC-Ni/YSZ catalyst. Through these measures, carbon deposition in the modified cells is mitigated, and therefore the steam/carbon (S/C) ratio for successful long-term cell operation is significantly lowered, and the cell durability is improved. A GDC-Ni/YSZ cell with extra catalyst is operated for over 1200 h directly on methanol under low S/C ratios at 750 °C and carbon deposition is considerably suppressed. In addition, the degradation mechanism of the cell directly fueled with nearly-dry methanol (S/C = 0.1) is investigated. This work provides insight into efficient and durable SOFCs using biofuels, towards renewable energy conversion in large-scale commercial applications. • Power generation from flat-tube SOFCs on nearly-dry methanol was studied. • An efficient wet impregnation method suitable for flat-tube SOFC was developed. • The coking tolerance of the anode decorated with Gd-doped ceria was improved. • Extra catalyst in fuel channels enhanced methanol conversion and coking tolerance. • Over 1200 h operation was attained under low steam/carbon (S/C) ratios at 750 °C. [ABSTRACT FROM AUTHOR]

A novel ionic cross-linked sulfonated poly(ether ether ketone) containing equal content of sulfonic acid and pendant tertiary amine groups (TA-SPEEK) has been initially synthesized for the application in direct methanol fuel cells (DMFCs). By adjusting the ratio of p -xylene dibromide to tertiary amine groups of TA-SPEEK, a series of ionic-covalent cross-linked membranes (C-SPEEK-x) with tunable degree of cross-linking are prepared. Compared with the pristine membrane, the ionic and ionic-covalent cross-linked proton exchange membranes (PEMs) exhibit reduced methanol permeability and improved mechanical properties, dimensional and oxidative stability. The proton conductivity and methanol selectivity of protonated TA-SPEEK and C-SPEEK-x at 25 °C is up to 0.109 S cm −1 and 3.88 × 10 5 S s cm −3 , respectively, which are higher than that of Nafion 115. The DMFC incorporating C-SPEEK-25 exhibits a maximum power density as high as 35.3 mW cm −2 with 4 M MeOH at 25 °C (31.8 mW cm −2 for Nafion 115). Due to the highly oxidative stability of the membrane, no obvious performance degradation of the DMFC is observed after more than 400 h operation, indicating such cost-effective ionic-covalent cross-linked membranes have substantial potential as alternative PEMs for DMFC applications. [ABSTRACT FROM AUTHOR]

Cross-linked sulfonated polyimides are one of the most promising materials for proton exchange membrane (PEM) applications. However, these cross-linked membranes are difficult to reprocess because they are insoluble. In this study, a series of cross-linkable sulfonated polyimides with flexible pendant alkyl side chains containing trimethoxysilyl groups is successfully synthesized. The cross-linkable polymers are highly soluble in common solvents and can be used to prepare tough and smooth films. Before the cross-linking reaction is complete, the membranes can be reprocessed, and the recovery rate of the prepared films falls within an acceptable range. The cross-linked membranes are obtained rapidly when the cross-linkable membranes are immersed in an acid solution, yielding a cross-linking density of the gel fraction of greater than 90%. The cross-linked membranes exhibit high proton conductivities and tensile strengths under hydrous conditions. Compared with those of pristine membranes, the oxidative and hydrolytic stabilities of the cross-linked membranes are significantly higher. The CSPI-70 membrane shows considerable power density in a direct methanol fuel cell (DMFC) test. All of these results suggest that the prepared cross-linked membranes have great potential for applications in proton exchange membrane fuel cells. [ABSTRACT FROM AUTHOR]

The initial step of methanol dehydrogenation on M(111) (M Cu, Pd and PdZn) surfaces is investigated based on the GGA-PW91 functions and periodic slab models in the framework of the first principles. To determine the preferred reaction pathway on M(111) surfaces, the transition states, reaction energies and energy barriers are quantified for the O H and C H cleavage pathways at the initial step of methanol dehydrogenation. The surface energy and the density of states (DOSs) for the methanol molecule over the M(111) surfaces are compared and analyzed to explain the initial hydrogen abstraction process of methanol molecule. The results indicate that the O H bond cleavage resulting in the co-adsorbed methoxyl and hydrogen atom is preferred on Cu(111) and PdZn(111) surfaces, while the C H bond cleavage with the formation of co-adsorbed hydroxymethyl and hydrogen atom is adapted on the Pd(111) surface. On the PdZn(111) surface, the methanol molecule possesses a higher surface energy than other two slabs. The behaviors of methanol dehydrogenation on M(111) surfaces are influenced by the d-electron structures of M(111). The initial hydrogen abstraction pathways of methanol molecule on the Cu(111) surface and the PdZn(111) surfaces are identical due to the similar d-electron structure near the Fermi level. [ABSTRACT FROM AUTHOR]

Superlattice arrays, an important type of nanomaterials, have wide applications in catalysis, optic/electronics and energy storage for the synergetic effects determined by both individual metals and collective interactions. Herein, a simple one-pot solvothermal coreduction approach is developed for facile preparation of bimetallic PtAu alloyed superlattice arrays (PtAu SLAs) in oleylamine, with the assistance of urea via hydrogen bonding induced self-assembly. Urea is essential in morphology-controlled process and prevents PtAu nanoparticles from the disordered aggregation. The characterization and formation mechanism of PtAu SLAs are investigated in details. The as-synthesized hybrid nanocrystals exhibit enhanced electrocatalytic performances for oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in alkaline electrolyte in comparison with commercial Pt-C (50%, wt.%) and Pt black catalysts. [ABSTRACT FROM AUTHOR]

Poor electrocatalytic activity, insufficient operation durability and low carbon monoxide (CO) tolerance of the Pt-based catalysts are key challenges facing the direct methanol fuel cells (DMFCs) as promising electrochemical energy conversion device. We here present a new effort to catalyst designed by depositing Pt nanoparticles on two-dimensional (2D) TaC-nanosheet/graphene hybird (Pt/TaC-G) to obtain notable improvement in electrocatalytic performance over the commercial Pt/C. Experiment results from both X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) support that a strong synergetic chemical coupling interaction between the Pt nanoparticles and the 2D TaC-G significantly enhanced electrocatalytic activity for methanol oxidation reaction (MOR). This process can improve the CO tolerance as well as durability of MOR catalysts simultaneously, making it a promising general approach to design and optimize the next generation electrocatalysts in DMFCs. [ABSTRACT FROM AUTHOR]

A novel alcohol fuel cell is constructed by using Fe 3+ as the oxidation agent instead of the conventional O 2 . Various alcohols as the fuels are tested, including methanol, ethanol, n -propanol and iso -propanol. In this fuel cell, the anode catalysts tested are PdSn/β-cd-CNT, PdSn/CNT, Pd/β-cd-CNT, Pd/CNT and Pd/β-cd-C, prepared by using multi-walled carbon nanotube (CNT) and carbon powder (C), as well as β-cyclodexdrin (β-cd) modified CNT (β-cd-CNT) and β-cd modified C (β-cd-C), as the substrates to immobilize PdSn and Pd nanoparticles in glycol solvent. The as-synthesized PdSn/β-cd-CNT catalyst presents significantly higher electroactivity for alcohol oxidation than the conventional Pd/C catalyst. Fe 3+ reduction reaction is carried out on the cathode made of carbon powder. The anolyte (alcohols in 1 mol L −1 NaOH) and catholyte (Fe 3+ in 0.5 mol L −1 NaCl) are separated with a Nafion 117 membrane. Open circuit voltage (OCV) of the cell with the anode PdSn/β-cd-CNT is 1.14–1.22 V, depending upon the used alcohol. The maximum power densities with methanol, ethanol, n -propanol and iso -propanol fuels are 15.2, 16.1, 19.9 and 12.2 mW cm −2 , respectively. [ABSTRACT FROM AUTHOR]

Ni-Mo-Ce 0.8 Sm 0.2 O 1.9 (SDC) composites are prepared and investigated as anodes of solid oxide fuel cells with methanol as fuel. The addition of Mo improves the catalytic activity for methanol pyrolysis and the resistance to carbon deposition of Ni-SDC anode. The anode with a mole ratio of Mo to Ni of 0.03:1 exhibits the lowest polarization resistance. The cell with that anode and SDC-carbonate composite electrolyte shows a maximum power density of 680 mW cm −2 at 700 °C. The stability of the cell is enhanced with the increase of the content of Mo in the anode, which is mainly attributed to the decreased amount of carbon deposits with a high graphitization degree. [ABSTRACT FROM AUTHOR]

Nanoporous (NP) PdZr alloy with controllable bimetallic ratio is successfully fabricated by a simple dealloying method. By leaching out the more reactive Al from PdZrAl precursor alloy, NP–PdZr alloy with smaller ligament size was generated, characterized by the nanoscaled interconnected network skeleton and hollow channels extending in all three dimensions. Upon voltammetric scan in acid solution, the dissolution of surface Zr atoms generates the highly active Pd–Zr surface alloy with a nearly pure Pd surface and Pd–Zr alloy core. The NP–Pd 80 Zr 20 surface alloy exhibits markedly enhanced specific and mass activities as well as higher catalytic stability toward oxygen reduction reaction (ORR) compared with NP–Pd and the state–of–the–art Pt/C catalysts. In addition, the NP–Pd 80 Zr 20 surface alloy shows a better selectivity for ORR than methanol in the 0.1 M HClO 4 and 0.1 M methanol mixed solution. X–ray photoelectron spectroscopy and density functional theory calculations both demonstrate that the weakened Pd–O bond and improved ORR performances in turn depend on the downshifted d–band center of Pd due to the alloying Pd with Zr (20 at.%). The as–made NP–PdZr alloy holds prospective applications as a cathode electrocatalyst in fuel–cell–related technologies with the advantages of superior overall ORR performances, unique structure stability, and easy preparation. [ABSTRACT FROM AUTHOR]

High-temperature direct methanol fuel cells (HT-DMFCs) show extensive application prospects in the future. However, the sluggish kinetics of oxygen reduction reaction (ORR) and unsatisfied methanol tolerance at cathode severely restrict its application. Herein, phosphotungstic acid H 3 PW 12 O 40 (HPW) is exploited to promote the methanol tolerance ability of cathode catalyst with enhanced ORR activity, thus boosting HT-DMFCs performance. Attenuated adsorption energy of methanol on Pt surfaces achieved by HPW modification restrains the occurrence of competitive methanol oxidation side reaction. Reinforced anti-poisoning capability of Pt with optimal d-band center modulated by HPW facilitates the removal of methanol oxidation intermediates, guaranteeing more available active sites for ORR and thus resulting in excellent cathode activity. Accordingly, the as-fabricated platinum-based catalyst achieves a high peak power density of 149 mW cm−2 in HT-DMFCs, surpassing the performance of majority reported literature. This work provides guidance to develop satisfactory methanol resistant ORR electrocatalyst for HT-DMFCs. [Display omitted] • HPW modification reduced adsorption energy of methanol and CO intermediates on Pt. • Pt-HPW-PDDA-CNTs exhibited significantly enhanced methanol tolerance capability. • HT-DMFCs with Pt-HPW-PDDA-CNTs cathode showed high power density. [ABSTRACT FROM AUTHOR]

Methanol crossover due to the low selectivity of proton exchange membranes is a long-standing issue in direct methanol fuel cell technology. Here we attempt to address this issue by designing a composite membrane fabricated by sandwiching a monolayer graphene between two thin Nafion membranes to take advantage of monolayer graphene's selective permeability to only protons. The methanol permeability of the present membrane is demonstrated to have a 68.6% decrease in comparison to that of the pristine Nafion membrane. The test in a passive direct methanol fuel cell (DMFC) shows that the designed membrane retains high proton conductivity while substantially suppressing methanol crossover. As a result, the present membrane enables the passive DMFC to exhibit a decent performance even at a methanol concentration as high as 10.0 M. [ABSTRACT FROM AUTHOR]

A simple and effective approach for the tight anchoring of molybdenum disulfide (MoS 2 ) to the surface of supercritical-alcohol-reduced graphene oxide (SRGO) is developed. The MoS 2 -SRGO composites are synthesized by the one-pot deposition of MoO 2 on SRGO and simultaneous reduction of GO to SRGO in supercritical methanol followed by sulfurization. The obtained MoS 2 -SRGO composites contain a crystalline MoS 2 phase comprising 11–14 layers of MoS 2 . In addition, the composites have mesoporous structures with high porosities, ranging between 55 and 57%. In comparison with bare MoS 2 and SRGO, the MoS 2 -SRGO composites have enhanced electrochemical performances due to their mesoporous structures and the synergetic effect between MoS 2 and SRGO sheets. When tested as the anode in a secondary lithium battery, it shows high reversible capacity of 896 mAh g −1 at 50 mA g −1 after 50 cycles, a high rate capacity of 320 mAh g −1 at a high charge-discharge rate of 2.5 A g −1 , and long-term cycling of 724 mAh g −1 at 50 mA g −1 after 200 cycles. This unique synthetic approach effectively and tightly anchors MoS 2 nanoparticles to the SRGO surface, resulting in improved structural integrity, electron transfer efficiency between the SRGO sheets and MoS 2 , and Li-ion diffusion kinetics. [ABSTRACT FROM AUTHOR]

A series of copper ion substituted MAl 2 O 4 (M = Mg, Mn, Fe and Zn) spinels is prepared by a single step solution combustion synthesis (SCS) and tested for methanol steam reforming (MSR). The copper ion substituted Cu 0.1 Fe 0.9 Al 2 O 4 appears to be the most active, showing ∼98% methanol conversion at 300 °C with ∼5% CO selectivity at GHSV = 30,000 h −1 and H 2 O:CH 3 OH = 1.1. The analogous impregnated catalyst, CuO (10 at%)/FeAl 2 O 4 , is found to be much less active. These materials are characterized by XRD, H 2 -TPR, BET, HRTEM, XPS and XANES analyses. Spinel phase formation is highly facilitated upon Cu-ion substitution and Cu loading beyond 10 at% leads to the formation of CuO as an additional phase. The ionic substitution of copper in FeAl 2 O 4 leads to the highly crystalline SCS catalyst containing Cu 2+ ion sites that are shown to be more active than the dispersed CuO nano-crystallites on the FeAl 2 O 4 impregnated catalyst, despite its lower surface area. The as prepared SCS catalyst contains also a portion of copper as Cu 1+ that increases when subjected to reforming atmosphere. The MSR activity of the SCS catalyst decreases with time-on-stream due to the sintering of catalyst crystallites as established from XPS and HRTEM analyses. [ABSTRACT FROM AUTHOR]

In this work, a novel non-platinum group metals (non-PGM) catalyst based on modified zinc 2-methylimidazole metal-organic framework (ZIF-8) is proposed and used for electrooxidation of methanol. Nano-sized particles of nonporous ZIF-8 are synthesized at room temperature using a simple template-free method. The synthesized ZIF-8 nanoparticles are characterized by X-ray diffraction, scanning electronic microscopy and nitrogen adsorption-desorption techniques. In order to decrease the overvoltage of methanol oxidation on carbon paste electrode (CPE), nickel species doped ZIF-8 modified carbon paste electrode (Ni/ZIF-8CPE) is fabricated as a modified electrode. Electrochemical techniques such as cyclic voltammetry and chronoamperometry are used to investigate the electrocatalytic activity of Ni/ZIF-8CPE toward methanol oxidation in alkaline solution. Cyclic voltammetry results show that oxidation current is considerably increased using Ni/ZIF-8CPE in comparison with unmodified CPE. Catalytic rate constant of methanol oxidation on Ni/ZIF-8CPE is obtained using chronoamperometric studies. Besides the good catalytic activity of the modified electrode toward methanol oxidation, it has other advantages such as simple preparation, ease of operation, good stability and low cost, which can be promising in the field of preparation of non-PGM electrocatalysts for application in fuel cells. [ABSTRACT FROM AUTHOR]

Porous Pt–Cu alloy networks are synthesized through a one-pot hydrothermal process, with ethylene glycol as the reducing agent and the block copolymer Pluronic F127 as structure-directing agent. The structure, porosity and surface chemical state of as-prepared Pt–Cu alloy with different composition are characterized. The formation mechanism of the porous structure is investigated by time sequential experiments. The obtained Pt 53 Cu 47 alloy possesses a unique 3D hierarchical porous network structure assembled by interconnected nanodendrites as building blocks. Because of the high surface area, concave surface topology and open porous structure, the Pt 53 Cu 47 alloy catalyst exhibits enhanced catalytic activity towards methanol and ethanol electro-oxidation in comparison with commercial Pt black and the Pt 73 Cu 27 alloy synthesized following the same process as Pt 53 Cu 47 . [ABSTRACT FROM AUTHOR]

Highly active Al-doped CuMnO x catalyst supported on metallic copper foam was prepared via the combustion method and placed adjacent to the anode electrocatalyst of a high temperature PEM fuel cell operating at 200–210 °C. The addition of aluminum oxide in the catalyst composition enhanced the specific surface area (19.1 vs. 8.6 m 2 g −1 ) and the reducibility of the Cu–Mn spinel oxide. Accordingly, the catalytic performance of CuMnO x was also improved. The doped sample is up to 2.5 times more active than the undoped sample at 200 °C, depending on the methanol concentration at the inlet, while CO selectivity is less than 0.8% in all cases. A membrane-electrode assembly comprising the ADVENT cross-linked TPS ® high-temperature polymer electrolyte was integrated with the Cu-based methanol reformer in an Internal Reforming Methanol Fuel Cell (IRMFC). In order to avoid extensive poisoning of the reforming catalyst by H 3 PO 4 , a thin separation plate was placed between the reforming catalyst and the electrooxidation catalyst. Preliminary results obtained from a single-cell laboratory prototype demonstrated the improved functionality of the unit. Indeed, promising electrochemical performance was obtained during the first 24 h, during which the required H 2 for achieving 580 mV at 0.2 A cm −2 , was supplied from the reformer. [ABSTRACT FROM AUTHOR]

In this work, a simple, rapid and facile one-pot wet-chemical co-reduction method is developed for synthesis of bimetallic Au–Pt alloyed nanochains supported on reduced graphene oxide (Au–Pt NCs/RGO), in which caffeine is acted as a capping agent and a structure-directing agent, while no any seed, template, surfactant or polymer involved. The as-prepared nanocomposites display enlarged electrochemical active surface area, significantly enhanced catalytic activity and better stability for methanol and ethylene glycol oxidation, compared with commercial Pt–C (Pt 50 wt%), PtRu–C (Pt 30 wt% and Ru 15 wt%) and Pt black. [ABSTRACT FROM AUTHOR]

A self-sustained, complete and miniaturized methanol fuel processor has been developed based on modular integration and microreactor technology. The fuel processor is comprised of one methanol oxidative reformer, one methanol combustor and one two-stage CO preferential oxidation unit. Microchannel heat exchanger is employed to recover heat from hot stream, miniaturize system size and thus achieve high energy utilization efficiency. By optimized thermal management and proper operation parameter control, the fuel processor can start up in 10 min at room temperature without external heating. A self-sustained state is achieved with H 2 production rate of 0.99 Nm 3 h −1 and extremely low CO content below 25 ppm. This amount of H 2 is sufficient to supply a 1 kW e proton exchange membrane fuel cell. The corresponding thermal efficiency of whole processor is higher than 86%. The size and weight of the assembled reactors integrated with microchannel heat exchangers are 1.4 L and 5.3 kg, respectively, demonstrating a very compact construction of the fuel processor. [ABSTRACT FROM AUTHOR]

The current study addresses, for the first time, the enhanced direct electro-oxidation of formic acid (FA) at platinum-nanoparticles modified glassy carbon (nano-Pt/GC) electrode in the presence of methanol (MeOH) as a blending fuel. This enhancement is probed by: (i) the increase of the direct oxidation current of FA to CO 2 ( I p d , dehydrogenation pathway), (ii) suppressing the dehydration pathway ( I p ind , producing the poisoning intermediate CO) and (iii) a favorable negative shift of the onset potential of I p d with increasing the mole fraction of MeOH in the blend. Furthermore, the charge of the direct FA oxidation in 0.3 M FA + 0.3 M MeOH blend is by 14 and 21times higher than that observed for 0.3 M FA and 0.3 M MeOH, respectively. MeOH is believed to adsorb at the Pt surface sites and thus disfavor the “non-faradaic” dissociation of FA (which produces the poisoning CO intermediate), i.e., MeOH induces a high CO tolerance of the Pt catalyst. The enhanced oxidation activity indicates that FA/MeOH blend is a promising fuel system. [ABSTRACT FROM AUTHOR]

Catalyst supports are known to play important role in governing overall catalyst activity and durability. Here, a new type of SnO 2 –TiO 2 solid solution (Ti x Sn 1-x O 2 ) support was prepared via a solvothermal method with substitution of Ti 4+ by Sn 4+ in the TiO 2 lattice. Furthermore, the Ti x Sn 1-x O 2 was combined with conventional carbon black (Vulcan XC-72) to prepare a hybrid support (Ti x Sn 1-x O 2 –C) for depositing Pt nanoparticles. The ratios of Sn vs. Ti in the solid-solution and Ti x Sn 1-x O 2 vs . XC-72 were systematically optimized in terms of their performance as supports for methanol oxidation. Compared to Pt/TiO 2 –C and commercial Pt/C catalysts, the best performing Pt/Ti 0.9 Sn 0.1 O 2 –C catalyst exhibited the highest activity, evidenced by methanol oxidation and CO stripping experiments. The well-dispersed Pt nanoparticles (2–3 nm) are mostly deposited on the boundaries of Ti 0.9 Sn 0.1 O 2 and carbon blacks. Formation of the special triple junction structure can play an important role in improving Pt utilization with increased electrochemical active surface areas (ESA) of Pt. In addition, the enhanced activity for Pt supported on Ti 0.9 Sn 0.1 O 2 –C is due to high content of OH group on Ti 0.9 Sn 0.1 O 2 along with the strengthened metal-supports interactions. Both promote the oxidation of poisoning CO absorbed on Pt active sites. [ABSTRACT FROM AUTHOR]

Nickel based catalysts have been studied as catalysts for either organic compound (especially methanol) oxidation or oxygen evolution reactions in alkaline medium for decades, but methanol oxidation and oxygen evolution reactions occur at a similar potential range and pH with nickel based catalysts. In contrast to previous studies, we studied these two reactions simultaneously under various pH and methanol concentrations with electrodes containing a series of NiOOH surface concentrations. We found that nickel based catalysts are more suitable to be used as oxygen evolution catalysts than methanol oxidation catalysts based on the observation that: The rate-determining step of methanol oxidation involves NiOOH, OH − and methanol while high methanol to OH − ratio could poison the NiOOH sites. Since NiOOH is involved in the rate-determining step, methanol oxidation suffers from high overpotential and oxygen evolution is favored over methanol oxidation in the presence of an equivalent amount (0.1 M) of alkali and methanol. [ABSTRACT FROM AUTHOR]