•Put forward a new kind of lithium-oxygen battery with double-gas-path structure and porous anode.•The novel battery structure can reduce the corrosion of lithium metal and the growth of dendrite.•Compared with the traditional structure battery, the new battery has a good cycle performance.A lithium–oxygen battery of double-gas-path structure and porous anode is presented in this work. Different from traditional structure battery, porous anode and the gas channel of anode side are used to provide argon gas for the battery. In order to protect the anode from corrosion of oxygen which penetrates from the cathode to the anode by dynamic gas-phase equilibrium. The improvement of the battery performance is attributed to the novel structure that can protect lithium metal from the corrosion of oxygen and it also reduces the growth of dendrite. The lithium–oxygen battery based on double-gas-path structure shows long cycle life (38 cycles), high discharge specific capacity (2510 mAh g−1) and specific energy density (7200 W h kg−1). More importantly, this work will also provide new ideas and methods for the research of other metal-air battery.

•Gradient design is implemented through double layer construction of cathode catalyst layer.•Three Pt/C ratio gradients: 60-60, 40–70, 70–40, (wt%, inner – outer layer), are evaluated.•Three Nafion ionomer content gradients (wt%): 24.5–24.5, 33–23, 40–20, are examined.•The optimal design is 70–40 for Pt/C ratio gradient, and 33–23 for Nafion content gradient.•The gradient design is found to be particularly effective at low humidity conditions.In order to increase the utilization of Pt, reduce mass transfer loss and improve the performance of polymer electrolyte membrane fuel cells (PEMFCs) under low humidity and high current densities, the cathode catalyst layers with two layers of different Pt/C ratio and Nafion content are fabricated and evaluated. Polarization curves (IVs), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are employed to characterize and compare the effects of Pt/C ratio and Nafion content gradient on the performance of PEMFCs under different humidification conditions. The results indicate that the performance of the membrane electrode assembly (MEA) can be significantly improved via allocating more Nafion and Pt/C in the sublayer near the membrane in cathode catalyst layer. The MEA with optimal gradient cathode catalyst layer results in improved catalysts utilization compared to MEA with single cathode catalyst layer, 0.403 g kWrated−1 and 0.711 g kWrated−1 under 80 RH% and 20 RH%, respectively. The areal power density of the optimal MEA is 28.4% and 135.7% higher than the conventional single-layer catalyst layer MEA under high and low humidity, respectively.

•A hydrogen containers and single cells coupling structure for heat coupling is proposed.•A heat coupled novel fuel cell stack and system is developed.•Experimental results prove that the coupling structure works well for heat management.Air-cooled, self-humidifying hydrogen fuel cells are often used for backup and portable power sources, with a metal hydride used as the hydrogen storage material. To provide a stable hydrogen flow to the fuel cell stack, heat must be provided to the metal hydride. Conventionally, the heat released from the exothermic reaction of hydrogen and oxygen in the fuel cell stack to the exhaust air is used to heat a separate metal hydride container. In this case, the heat is only partially used instead of being more closely coupled because of the heat transfer resistances in the system.To achieve better heat integration, a novel scheme is proposed whereby hydrogen storage and single fuel cells are more closely coupled. Based on this idea, metal hydride containers in the form of cooling plates were assembled between each pair of cells in the stack so that the heat could be directly transferred to a metal hydride container of much larger surface-to-volume ratio than conventional separate containers. A heat coupled fuel cell portable power source with 10 cells and 11 metal hydride containers was constructed and the experimental results show that this scheme is beneficial for the heat management of fuel cell stack.

•Comprehensive analysis of failure mechanism for MEA.•Reinforced matrix thinning in the PTFE/Nafion composite membrane.•Pinholes are formed at the outlet region of the composite membrane.•Pt particles grow along the flow channel.Durability is one of the key issues in commercialization of proton exchange membrane fuel cell (PEMFC). The main purpose of this study is to investigate the degradation mechanism of Membrane Electrode Assembly (MEA) based on PTFE/Nafion composite membrane in PEMFC through the MEA/Stack Durability Protocol developed by the Fuel Cell Technical Team (FCTT) of the Freedom CAR and Fuel Partnership. The accelerated life test lasted for 300 h, with voltage decay rate of the MEA about 0.48 mV/h at operating current density 100 mA/cm2 being achieved. After the acceleration experiment, degradation mechanisms for the MEA based on PTFE/Nafion composite membrane were analyzed in detail by hydrogen-thermal experiment, SEM, TEM, EDS and Ion Chromatographic test. The experimental results show that pinhole formed at outlet position of the composite membrane leads to hydrogen crossover current density exceeding 21 mA/cm2 at 210 h, with F− and SO42− concentrations sharply increased around 200 h in discharge water of fuel cell from IC results, therefore, membrane failure is the major factor in the failure of MEA. Moreover, the micro-structural damage in the MEA and Pt particles growing up along flow channel even appearing at membrane could be observed from SEM, TEM and EDS results, which play important role in the deterioration of performance and stability for PEMFC.

•A simple and effective approach was developed to improve the durability and properties of PEMFC.•The durability of the CCMs was tested by the DOE CCM/stack durability test protocol.•The chemical degradation of Nafion ionomer was mitigated by adding PTA to catalyst layer.•Durability and performance of the CCM were improved by adding PTA into the catalyst layer.The aim of this study was to enhance durability and performance of Polymer Electrolyte Membrane Fuel Cells (PEMFCs) for transportation application. A modified catalyst coated membrane (CCM) with phosphotungstic acid (PTA) in catalyst layer was fabricated using a heating ultrasonic-spray method, and durability study of both the modified CCM and traditional CCM was carried out according to the DOE CCM/stack durability protocol. During the accelerated stress test of CCM durability, cyclic voltammetry, polarization curves, linear sweep voltammetry and electrochemical impedance spectroscopy were employed for diagnosis of the CCM performances. The experimental results indicate that the power density of the modified CCM decreased only 14% while the traditional CCM decreased 33% after 100-h aging time, which confirms that addition of PTA in the catalyst layer of CCM is an effective way to improve the durability for CCM attributed to the enhancement of intermediates removal and the increasing of proton transfer channels by using the PTA excellent properties, both redox property and proton conductivity.

•A PEMFC life test using the drive cycle test protocol technique from Chinese NERC.•Durability decay rate of the PEMFC is about 70 μV h−1 at 500 mA cm−2.•Hydrogen crossover in membrane is a decisive factor leading to MEA failure.•Structure change in catalyst layer is a major factor of MEA degradation.One of important factors determining the lifetime of proton exchange membrane fuel cells (PEMFCs) is degradation and failure of membrane electrode assembly (MEA). The lack of effective mitigation methods is largely due to the currently limited understanding of the degradation mechanisms for fuel cell MEAs. This study adopted the accelerating degradation technique to analyze durability of MEA using drive cycle test protocol developed by Chinese NERC Fuel Cell & Hydrogen Technology to assess the long-term durability of fuel cells for vehicular application. During 900 h durability test of the MEA, the polarization curve, cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were performed as diagnostics during and on completion the test. The experimental results show that the performance degradation rate of the cell is about 70 μV h−1 at the operating current density of 500 mA cm−2, failure of the proton exchange membrane is the decisive factor leading to the failure of the MEA. And the damage of the micro-structural of catalytic layer, crucial for electrochemical reaction, is the decisive factor for the performance degradation.

•Notable thermal stability of LSGM-carbonate composite electrolytes.•Relatively stable conductivity during a 650 h ageing test at 600 °C in air.•Maximum power density of 617 W cm−2 and the OCV of 1.01 V at 600 °C.Novel composite materials based on La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM) and a binary eutectic carbonates (52 mol% Li2CO3:48 mol% Na2CO3) are potential electrolytes for low-temperature solid oxide fuel cells (LTSOFCs) operating at 400–600 °C. However, thermal stability of the LSGM–(Li/Na)2CO3 composites remains in doubt due to the molten state of the carbonates at elevated temperature. In this paper, XRD, SEM, TGA and EIS were employed for thermal ageing and cycling studies of the LSGM–(Li/Na)2CO3 composites. XRD and SEM results showed that ageing induced a slight effect on the structure and morphology of the composites. TGA and EIS results indicated that the composites had a good stability during cycling. The LSGM–20 wt% (Li/Na)2CO3 sample showed a relatively stable conductivity (7–9 × 10−2 S cm−1) during a 650 h measurement under air at 600 °C. Single cell based on the composite electrolytes was reported for the first time, a maximum power density of 617 W cm−2 and the open circuit voltage (OCV) of 1.01 V were achieved at 600 °C for the composite containing 20 wt% carbonates. The notable thermal stability together with fairly high performance emphasize the promise of LSGM–(Li/Na)2CO3 composite electrolytes for long-term LTSOFCs.

The research of advanced and green energy is getting more and more attention because the status quo of the energy shortage and the environment pollution is worse and worse, lithium-air batteries are attracting considerable interest for their high theoretical specific energy and pollution-free. Nevertheless their performance is restricted by many factors, for instance the transfer tunnel for the oxygen is blocked by the discharge products and then the discharge is over ahead of time. In this paper we had prepared the air electrode with double-layer structure which is usually used in proton exchange membrane fuel cell (PEMFC) to increase the discharge capacity, the discharge special capacity of the air electrode could reach 6587 mAh/g of carbon at the rate of 0.15 mA/cm2.Highlights► The related technologies of fuel cells and lithium-ion batteries are combined. ► The air electrode is prepared with double-layer structure. ► Carbon paper acts as gas diffusion layer and catalyst layer is prepared by spraying. ► The batteries obtained a high-capacity of 6587 mAh/gcarbon at the rate of 0.15 mA/cm2.

In this work, we presented the novel anode flow field for direct dimethyl ether fuel cell (DDFC). The anode flow field of the DDFC consisted of hydrophilic, hydrophobic, and diffusion region (with a ratio of region areas of 3:6:1). The maximum power density of the DDFC with novel anode flow field was 67 mW cm−2, which was higher than that of the cell fed with conventional flow field (60 mW cm−2). The electrochemical impedance spectra analyses revealed that the mass transfer resistance of novel anode flow field was lower than that of conventional flow field. The constant current operation curves showed that the performance decay ratio of the novel anode flow field was lower than that of conventional one. It indicated that the novel flow field benefited the long-term operation of DDFC.Highlights► The flow field is consisted of hydrophilic, hydrophobic and diffusion region. ► The novel flow field decreases the mass transfer resistance. ► The novel flow field increases the utilization of DME fuel. ► The maximum power density of the DDFC can reach 67 mW cm−2.

The corrosion behavior of titanium (TA2), boron-doped diamond (BDD) coated titanium and mixed metal oxide (MMO) coated titanium were studied using electrochemical impedance spectrum (EIS) in simulated solid polymer electrolyte (SPE) water electrolyte conditions at 80 °C. At imposed anodic potential, after about 240 h electrolysis, the bigger capacitance and reaction resistance values were observed for MMO coated titanium material, which demonstrated that MMO coated titanium has more corrosion-resistance performance. SEM photos showed that ten days electrolysis don't do much harm to MMO coated titanium material in simulated SPE water electrolysis environment.Highlights► Titanium and coatings on titanium as bipolar plates. ► Evaluating bipolar plates performance using in-situ EIS when electrolyzing. ► MMO coated TA2 material is a best candidate.

Although hydrogen fuel cells have attracted so much attentions in these years because of the application prospect in electric vehicles, some obstacles have not been solved yet, among which hydrogen storage is one of the biggest. Direct borohydride fuel cell (DBFC) is another choice without hydrogen storage problem because borohydride is used as reactant directly in the fuel cell. In this paper, DBFC performance under different operation conditions was studied including electrolyte membrane type, operation temperature, borohydride concentration, supporting electrolyte and oxidant. Results showed that, with Pt/C and MnO2 as anode and cathode electrocatalyst, respectively, Nafion® 117 membrane as electrolyte, 1.0 M, 3.0 M and 6.0 M NaBH4 and H2O2 solution in NaOH as reactant solution, 80 °C operation, the peak power density could reach 130 mW/cm2.