•Laser-perforated gas diffusion layer to enhance liquid water transport from the electrode to the gas channels.•To enhance effectively the discharge of water, while avoiding the liquid droplets obstruct the gas flow channel.•The better value is a perforation diameter of 100 μm and a perforation interval of 2 mm.A laser was used to perforate gas diffusion layer (GDL) that enhances liquid water transport from the electrodes to the gas channels. The generated holes diameter is from 80 to 200 μm, and center-to-center spacing is from 1 to 3 mm. A three-dimensional numerical model, based on a level set method, was built to investigate the water transport characteristics through the perforations with different diameters and spacing. Experiments and simulation results show that there is a better correlation among the diameter, spacing of the perforation and the power density. When the perforation diameter is 100 μm and the perforation pitch is 2 mm, the water transfer effect is the best which enhances the water discharge effectively and avoids the liquid droplets obstructing the gas flow channel at the same time. These results may assist in the design of GDL for water management in the operation of proton exchange membrane fuel cells.

•Study the effect of carbon emissions by HCNG and CNG on proposed three ANOVA models.•Analyze the total amount of CO and CO2 by 20% HCNG and CNG from year 2000–2015.•Validate that carbon emissions produced by HCNG are less than by natural gas.Hydrogen enriched natural gas (HCNG) is widely studied in the energy field. It has two good characteristics inherited from hydrogen and compressed natural gas (CNG): 1) relatively cheap; and 2) operational safety. It also can reduce the emission of NOx and HC. Hence, it is a good alternative hydrogen transitional fuels. However, there is very limited work done by statistical analysis on HCNG and CNG. To address with this issue, we use analysis of variance (ANOVA) analysis to study the HCNG and CNG as fuel, and propose three statistical models tailored to the data of CO and CO2 emissions produced by HCN and CNG from year 2000–2015 from different industry sectors and different regions in China. Through the analysis, we concluded that CO and CO2 emissions produced by HCNG are statistically significant less than CO and CO2 produced by CNG.

•Review the recent development of the PEMs prepared by ATRP.•According to the different monomers in the polymerization, these membranes are discussed.•Present the perspectives of PEMs prepared via ATRP.Proton exchange membranes (PEMs) with well-defined microphase separation hold great promise for satisfying the demands of operation under high temperature and low humidity. Atom transfer radical polymerization (ATRP), as one of the most popular methods of controllable polymerization, has already been one of the most convenient tools for the synthesis of copolymers with well-defined microphase separated structures. This article tersely and concisely reviews the recent development of the PEMs prepared by ATRP for proton exchange membrane fuel cells. According to the different functional monomers in the polymerization, three kinds of membranes are systematically discussed in this feature article. The first membrane is made of copolymer grafted styrene by ATRP followed by post-sulfonation; the second membrane is prepared by directly grafting a sulfonated monomer to polymer using single-step ATRP; and the membranes grafted other types of monomers are divided into the third membranes. For each category of membrane, structures, properties, and their relationships are conducted targeted analysis. Finally, the perspectives of future trends on PEMs prepared via ATRP are presented.

•Employed MD simulations to study the FEP-g-SSt PEM model.•Used RDFs analysis to provide the microstructures inside the membranes.•Calculated diffusion coefficients of H2O and H3O+ inside the simulated membranes.•Calculated proton conductivities of the FEP-g-SSt-n (n = 14, 7, 4) membranes.In order to study the microstructure of the prepared potential proton exchange membrane (PEM), molecular dynamics (MD) simulations were used to lucubrate the transport behavior of water molecules and hydronium ions inside the hydrated sulfonated styrene grafted fluorinated ethylene propylene (FEP) membrane, which possess different side chain lengths. By evaluating the radial distribution functions (RDFs), it was observed that with increasing side chain length, the average sulfur-hydronium ion separation slightly increased and the coordination number of H3O+ around sulfonic acid groups decreased whereas larger water clusters formed. The results of the mean square displacements (MSDs) show that the proton conductivities of the membranes with the proposed side chain lengths were about three fifths of the experimental data, of which the membrane with side chain length of 7 sulfonic styrene units was supposed to exhibit the highest proton conductivity, that is 115.69 mS cm−1. All of the supposed membrane models presented good proton conductivity that could definitely meet the application requirements of the proton exchange membranes. The MD simulations can provide an insight to the chain structure of the radiation grafted membrane, and are of guidance significance to design other side-chain-structure polymers to be used as PEMs in proton exchange membrane fuel cells (PEMFCs).

•Models of poly (aryl ether oxadiazole) AEMs with the same degree of functionality were studied by MD simulation.•OH− conductivity of AEMs with three different imidazolium group positions were studied.•Simulation results showed OH− have more chances to appear around imidazole radical groups.Hydroxyl ionic conductivities of anion exchange membrane with three different imidazolium group positions were studied. Models of Poly (aryl ether oxadiazole) anion-exchange membranes with the same degree of functionality were investigated by molecular dynamics simulation. Mean square displacement (MSD) was applied for hydroxyl ions, H2O and methanol diffusion coefficient calculation. The distance of N+–N+, N–OH–O was analyzed using radial distribution function (RDF). Simulation results shown that hydroxyl ions had more chances to appear around imidazole radical groups. The hydroxyl ionic conductivity of Line-type, Meta-type and Diagonal-type respectively were 7.74 × 10−2 S·cm−1, 4.66 × 10−2 S cm−1 and 1.78 × 10−2 S cm−1. The diffusion rate of CH3OH molecules had the same trends with OH− particles, reducing from the Line-type to Diagonal-type.

•Microstructure of sulfonated polynorbornene membrane was discussed by radial distribution function simulation.•Diffusion coefficients and proton conductivity were calculated.•Difference of the simulated results and experimental values were discussed.•Predicted that this novel sulfonated polynorbornene membrane is suitable for fuel cells.A novel polymer material based on polynorbornenes prepared via ring-opening metathesis polymerization (ROMP) was intended to be used as proton exchange membranes. In order to study the microstructure and forecast their macro properties, molecular dynamics simulations were used to lucubrate the transport behavior of hydrated sulfonated polynorbornene-based (SPNB) proton exchange membrane at different temperatures. Simulation results have shown that SPNB membranes swell upon hydration and become phase segregated into hydrophobic and hydrophilic domains with sulfonic acid groups located at their interface. By evaluating the radial distribution function (RDF), it was observed that with increasing number of water molecules caused by the rising temperatures, which leading to more water molecules solvate the sulfur atoms and hydronium ions, the average sulfur-hydronium ion separation distance increased and larger water clusters formed. The results of the mean square displacements (MSDs) showed that the proton conductivity of the membrane with the designed structure was 0.056 S/cm which can meet the application requirements of the proton exchange membranes. Moreover, the simulated proton conductivities qualitatively followed the experimental data at 298 K, 323 K and 348 K, respectively. The molecular dynamics simulation can provide predictive performance of this designed polymer structure before its preparation, which is of guidance significance to the preparation of proton exchange membranes.

•The effect of mechanical vibration on dynamic response of PEMFC was investigated.•Liquid water formation and transport were investigated under the mechanical vibration.•The vibration causes the voltage oscillations of PEMFC is larger than under no vibration.The dynamic response of proton exchange membrane fuel cells (PEMFCs) under mechanical vibration is an important criterion in the application to automotive systems. The effect of mechanical vibration on dynamic response was investigated on an automobile vibrating platform. The PEMFC voltage was acquired according to the current density change under a variety of amplitude, frequency and air stoichiometry. Furthermore, liquid water formation and transport were investigated under the mechanical vibration by employing a transparent PEMFC. The results show that a new steady-state of the voltage under vibration and no vibration take about 50s and 20s respectively after the current density step. The PEMFC dynamic performance was slightly improved under amplitude at 4 mm, compared to operation at no vibration. Also, the voltage fluctuation was detected under the vibration, the small droplets merged into larger droplets is due to the sudden vibration. These larger droplets interfere with the mass-transfer process in the gas channels.

•New designed AEMs was synthesized by double quaternized monomer.•Ionic conductivity of P-HDHM-NB-hydroxide-12 reached 27 mS·cm−1 at room temperature.•After 16 days alkaline immersion, AEMs showed better alkaline stability.•Possibility of Hofmann elimination and Nucleophilic Substitution are compared.A novel monomer who combined cross linker and functional groups together called 2,2'-(hexane-1,6-diyl)bis(2-methyl-2,3,3a,4,7,7a-hexahydro-1H-4,7-methanoisoindol-2-ium) iodide (HDHM-iodide) was synthesized and polymerized by Ring-opening Metathesis Polymerization (ROMP) to give a series of anion exchange membranes. The resulting monomers and polymers were characterized by 1H and 13C NMR, TGA. Directly cast from the polymerization solution on flat glass to form the clear, flexible anion exchange membrane. Swelling ratio and water uptake are only 6.2% and 28.04% at 60 °C for membrane with 2.32 mmol·g−1 ion exchange capacity (IEC). The conductivity of Poly (HDHM-Norbornene-hydroxide-12) and Poly(HDHM-Norbornene-chlorine-12) AEMs at room temperature up to 27 mS·cm−1 and 14 mS·cm−1 separately, and increased with temperature quickly. After 16 days immersed in 2 M NaOH solution, conductivity and IEC dropped at 60 °C in alkaline solution, 50% and 35% separately. The energy barrier of degradation pathways calculation reveled that Hofmann Elimination case 2 degradation pathway with the lowest energy barrier 12.181 kcal·mol−1 is most likely occurred when faced with hydroxide. Also, the energy barrier of Hofmann Elimination is lower than Nucleophilic Substitution degradation mechanism.

•The DMFC anode and cathode polarization were investigated separately.•The polarization results were theoretical fitted and analyzed in detail.•An efficient MEA optimization way was provided by polarization distribution study.Membrane Electrode Assembly (MEA) is a key component of direct methanol fuel cell. In order to improve the power generation performance of the MEA, it is necessary to reduce polarization losses. The cathode and anode activation polarization, proton exchange membrane ohmic polarization and gas diffusion layer mass transfer polarization were studied under different methanol concentration and operation temperature conditions respectively. A theoretical study of the various polarization fitting and distribution losses was conducted. The polarization distribution results indicated that the activation polarization of cathode and anode are the main over potential contribution and accounted for more than 80%. The ohmic resistance accounted for approximately 10%. By studying the distribution of polarization loss, we got a variety of distribution of polarization losses under different operating conditions, these results provide a theoretical basis for efficient ways to optimize the MEA.

•EG/phenolic resin composite BP was prepared and tested.•Effects of resin solution concentrations on the performances of BPs were studied.•The water-soluble resin was 25%, the bipolar plate exhibited optimized properties.A series of expanded graphite/phenolic resin composite bipolar plates with different phenolic resin contents have been prepared by resin vacuum impregnation and hot press method. The alcohol-soluble and water-soluble phenolic resins were used as polymer filler and expanded graphite plate are used as substrate carbon plate. The results indicated that the tensile strength, flexural strength, resistivity, gas permeability and corrosion current density of bipolar plate are influenced by resin solution concentration. When the solution concentration of water-soluble phenolic resin is 25%, the bipolar plate exhibits better mechanical property and resistivity. The electrochemical impedance spectroscopy (EIS) result shows that the overall resistance of homemade expanded graphite/phenolic resin composite bipolar plate is lower than that of graphite bipolar plate. The composite bipolar plates should be a promising candidate for PEMFCs and vanadium redox flow battery application.

•Two novel cross-linked anion exchange membranes were synthesized via nucleophilic substitution reactions.•The synthesis routes simplified by rolling the crosslinking and functionalizing into one.•The crosslinking process enhanced the thermal and mechanical stabilities of membranes.•The thermal properties and durability of membranes in alkaline environments were enhanced.•The extensive conjugated structures of precursory polymer dispersed the electronic distributions of quaternary ammonium groups.Two novel cross-linked anion exchange membranes (AEMs) for alkaline fuel cells (AFCs) were synthesized via nucleophilic substitution reactions. Brominated poly(2,5-bis(perfluorophenyl)-1,3,4-oxadiazole-co-allyl bisphenol), called as precursory polymer (PP), was synthesized by reaction of 2,5-bis(2,3,4,5,6-pentafluorophenyl)-1,3,4-oxadiazole (FPOx) and diallyl bisphenol A (DABPA) followed by bromination. Ethanediamine (EDA) and propane diamine (PDA) were introduced to PP to obtain cross-linked polymers EDA-PP and PDA-PP, respectively. The reactions between PP and diamines rolled the crosslinking and functionalizing process in one. The crosslinking process enhanced the thermal and mechanical stabilities of EDA-PP and PDA-PP, which were affected by the length of alkyl chains of diamines. Meanwhile, the conjugated system of PP extended the electron clouds around the amine groups, which improved the thermal stability and alkaline durability of quaternary ammonium (QA) groups. The solution casting membranes of EDA-PP and PDA-PP showed high ionic conductivities. The swelling ratios, TGA and AFM properties of the membranes also demonstrated their good mechanical and thermal stabilities.

•Guanidinium-based alkaline anion exchange membrane was prepared and characterized.•The degradation mechanism of guanidinium cation in alkaline solution was studied.•The energy changes during the whole degradation reaction were analyzed.•Effects of OH− concentration and substituents on energy barriers were discussed.A guanidinium-functionalized anion exchange membrane (AEM) was prepared and characterized. The AEM stability in an alkaline environment and transition structures during the degradation process were studied with DFT (density functional theory)/B3LYP method, 6-31 + G (d) basis set. Experimental results and theoretical analysis showed that the second step (Step 2′) of degradation reaction was the control procedure; guanidinium cation was unstable under alkaline condition. It had lower energy barriers, which decided it was easier for the degradation reaction to occur in high pH environment. The ionic conductivity of AEM was 2.4 × 10−2 S cm−1 at 80 °C. However, the AEM soaked in 1 M NaOH solution, fragments were found after 10 days. The FTIR analysis showed that the structure of the membrane had been changed due to the attack of hydroxide ion. A new substance, tetramethylurea, had produced.

•Two types of anion exchange membranes were synthesized, they had larger conjugated system.•The conjugated effect were discussed by quantum calculation and morphology tests.•Double bonds in main polymer chain can easily cross-linked to enhance the membranes' structure.•Alkaline stability was examined by two different methods.A novel cross-linked pyridine anion exchange membrane was synthesized via thermal cross-linking methods. 2,5-bis(2,3,4,5,6-pentafluorophenyl)-1,3,4-oxadiazole (FPOx) and diallyl bisphenol A (DABPA) were reacted to obtain the main polymer chain (MP). MP was substituted with 4-bromopyridine and 4-hydroxypyridine to generate two pyridine polymers conjugated pyridine polymer (CPP) and non-conjugated pyridine polymer (NPP). The different conjugation statues of CPP and NPP led to distinct mechanical and electrochemical properties. The diallyl groups in MP acted as the cross-linking structures which strengthened the mechanical properties of CPP and NPP and provided more flexible side chains. The ultimate membrane CPP-membrane and NPP-membrane were prepared by solution casting methods. Compared with NPP-membrane, the ionic conductivity of CPP can achieve to 20.1 mS/cm at 20 °C with excellent mechanical and thermal characteristics. Quantum theory computation and AFM morphology were carried out to figure out the reason of the difference in ionic conductivities and physical properties.

Corrosion resistance performance of SS316L treated by passivation solution was investigated in a simulated environment of the passive direct methanol fuel cell (DMFC). Electrochemical impedance spectroscopic (EIS) test showed that polarization resistance of untreated and treated SS316L were 1191 Ω cm2 and 9335 Ω cm2, respectively. The above result agreed with the Tafel slope analysis of potentiodynamic polarization curves. Comparing the untreated and treated SS316L in the simulated environment of DMFC anode working conditions, it was observed that the corrosion current density of treated SS316L as estimated by 4000 s potentiostatic test reduced from 38.7 μA cm−2 to 0.297 μA cm−2, meanwhile, the current densities of untreated and treated SS316L in cathode working conditions were 3.87 μA cm−2 and 0.223 μA cm−2, respectively. It indicated that the treated SS316L should be suitable in both anode and cathode environment of passive DMFCs. The treated SS316L bipolar plates have been assembled in a passive single fuel cell. A peak power density of 1.18 mW cm−2 was achieved with 1 M methanol at ambient temperature.Highlights► We examine the corrosion resistance performance of a SS316L in a simulated environment of a passive direct methanol fuel cell (DMFC). ► A SS316L is treated, and used to do bipolar plates assembly in a passive DMFC. ► The bipolar plates not only avoid contaminating the catalyst and membrane, but also decrease the internal resistance of the DMFC.

Alkaline fuel cells suggest solution for the problems of low methanol oxidation kinetics and methanol crossover, which are limiting the development of direct methanol fuel cells. In this work, a novel anion exchange membrane, quaternized poly(aryl ether oxadiazole), was prepared through polycondensation, grafting and quaternization. The ionic conductivity of as-synthesized anion exchange membrane can reach up to 2.79 × 10−2 S/cm at 70 °C. The physical and chemical stability of the anion exchange membranes could also meet the requirement for alkaline direct methanol fuel cells.Highlights► We synthesize quaternized poly(aryl ether oxadiazole) membrane through polycondensation, grafting, brominating and quaternization. ► The membrane has good performance in methanol solution. ► Moreover, the Ion conductivity of the membrane reaches up to 2.90 × 10−2 S/cm. ► It may be used to be alkaline direct methanol fuel cells.

A series of fluorinated poly(aryl ether oxadiazole)s ionomers based on imidazolium salts (FPAEO-xMIM) were synthesized by quaternization of bromomethylated poly(aryl ether oxadiazole)s (FPAEO-xBrTM) with 1-methyl imidazole as aminating reagent. The anion exchange membranes (AEMs) were prepared by casting method and then immerged in aqueous sodium hydroxide for hydroxide ion exchanging. The structure of the obtained ionomers was characterized by 1H-NMR and FT-IR measurements. The physical and electrochemical properties of the membranes were also investigated. The hydroxide conductivity of FPAEO-xMIM membranes was higher than 10−2 S cm−1 at room temperature, while the water uptake and swelling ratio was moderate even at elevated temperature. TGA analysis revealed that the membranes based on imidazolium salts had good thermal stability.Highlights► Novel fluorinated poly(aryl ether oxadiazole)s anion exchange membranes were prepared. ► Conductivity of the anion membranes was higher than 10−2 S/cm at room temperature. ► The obtained anion membranes are promising for the application in AEMFCs.

The methanol concentrations, temperature and current were considered as inputs, the cell voltage was taken as output, and the performance of a direct methanol fuel cell (DMFC) was modeled by adaptive-network-based fuzzy inference systems (ANFIS). The artificial neural network (ANN) and polynomial-based models were selected to be compared with the ANFIS in respect of quality and accuracy. Based on the ANFIS model obtained, the characteristics of the DMFC were studied. The results show that temperature and methanol concentration greatly affect the performance of the DMFC. Within a restricted current range, the methanol concentration does not greatly affect the stack voltage. In order to obtain higher fuel utilization efficiency, the methanol concentrations and temperatures should be adjusted according to the load on the system.

The annealing treatment and pH were controlled to prepare a bimetallic PtRu/C anode catalyst by the citrate-stabilized chemical reduction method. X-ray diffraction and X-ray photoelectron spectra revealed that the catalyst before the annealing treatment showed smaller size particles mainly composed of metallic platinum and hydrous ruthenium oxide. The anhydrous RuO2 increased with increase in the annealing temperature from 250 °C to 400 °C. The linear sweep voltammetry (LSV) results showed that the non-annealed catalyst had the highest current density at a given potential. Also, the particle size varied with the stabilizing pH. A homogenous catalyst was prepared at a pH of 7 in the laboratory. The particle size was about 2.39 ± 0.46 nm with 14.62 at% ruthenium in the PtRu alloy. The maximum LSV current density was 66.4 mA mg−1 PtRu at 0.45 V with an onset potential of 0.12 V (versus SCE). The catalyst when tested in a single cell DMFC produced a power density of 67.5 mW cm−2 at a current density of 240 mA cm−2.

Electrochemical impedance spectroscopy (EIS) is widely used in fuel cell impedance analysis. However, for ohmic resistance (RO), EIS has some disadvantages such as long test period and complex data analysis with equivalent circuits. Therefore, the current interruption method is explored to measure the value of RO in direct methanol fuel cells (DMFC) at different temperatures and current densities. It is found that RO decreases as temperature increase, and decreases initially and then increases as current density increases. These results are consistent with those measured by the EIS technique. In most cases, the ohmic resistances with current interruption (RiR) are larger than those with EIS (REIS), but the difference is small, in the range from −0.848% to 5.337%. The errors of RiR at high current densities are less than those of REIS. Our results show that the RiR data are reliable and easy to obtain in the measurement of ohmic resistance in DMFC.