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In this study, the microstructure of carbon fiber paper is modified through H 3 PO 4 etching to enhance the electrolyzer performance. The effects of different H 3 PO 4 concentrations and different soaking times on the hydrogen evolution reaction are firstly investigated. The electrochemical test results show that the best performance of etched electrodes is achieved at a H 3 PO 4 concentration of 1 M and a soaking time of 12 h, with a significant reduction in charge transfer resistance and overpotential. Subsequently, to explore the change mechanism in electrochemical properties, the microstructure of the carbon paper is investigated using Scanning Electron Microscope (SEM) and Mercury Intrusion Porosimetry (MIP) tests, which show uniformly distributed micropores appear on the surface of the carbon fibers after etching, and the porosity increases from 0.74 to 0.8. Brunauer-Emmett-Teller (BET) tests show that the specific surface area of the carbon paper increases from 0.72 m2/g to 4.06 m2/g, which effectively increases the interfacial contact area between the catalyst layer and the liquid gas diffusion layer. Furthermore, a 3D multi-physics model is established to further elucidate the impact mechanism of changes in porosity, conductivity, and active specific surface area on the performance of anion exchange membrane electrolyzer, with changes in active specific surface area having the greatest effect. • Microporous structure of the carbon paper LGDL is modified by etching. • The etching method effectively improves the performance of AEMEL. • The increase in specific surface area and porosity greatly reduces the resistance. • Numerical modeling to analyze the impact of microscopic parameters on AEMEL. • LGDL with high specific surface area has a positive effect on AEMEL's development. [ABSTRACT FROM AUTHOR]

In light of environmental problems such as the depletion of hydrocarbon resources and global warming, the use of environment-friendly power production has become crucial nowadays. Hydrogen can serve as a globally friendly energy source because the byproduct of hydrogen combustion is only water. By a hydrothermal approach, we synthesized barium manganese oxide (BaMnO 3) embedded on reduced graphene oxide (rGO) as a competent electrocatalyst for OER. We utilized X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive x-rays (EDX), Brunauer Emmette Teller (BET) and Raman to determine the crystal structure, morphology, elemental composition, surface area and lattice phenomena of the fabricated rGO/BaMnO 3 nanocomposite. The BaMnO 3 agglomerated nanoparticles were incorporated into the mesoporous hollow carbon nanosheets to form amorphous textured embedded rGO/BaMnO 3. This enhanced the intrinsic reactivity of rGO/BaMnO 3 nanocomposite for the oxygen evolution reaction (OER) in addition to increasing the effective surface area of the electrolyte. The electrochemical outcomes demonstrate that synthesized nanocomposite exhibited an impressive Tafel slope (36 mV dec−1), lowest overpotential (202 mV) and remarkable stability over 35 h. Therefore, the fabricated nanocomposite displayed exceptional efficiency in OER process as well as for numerous other future applications. [Display omitted] • RGO/BaMnO 3 nanocomposite was fabricated via facile hydrothermal technique. • Various analytical techniques were conducted to evaluate the material's properties. • The developed material exhibit OER process, which can be initiated by applied electrocatalyst at 0.50 V vs RHE using 1.0 ssM KOH solution. • The rGO/BaMnO 3 nanocomposite exhibits the minimal overpotential (202 mV) with low Tafel slope (36 mV dec−1). • RGO decorated BaMnO 3 (rGO/BaMnO 3) exhibiting remarkable stability of 35 h tested via chronoamperometry. [ABSTRACT FROM AUTHOR]

The integration of reformers into high-temperature polymer electrolyte membrane (HT-PEM) fuel cells presents a significant opportunity to improve fuel flexibility and cost-effectiveness. To understand their degradation, we applied two start–stop cycling procedures: one with pure H 2 and another with an 80 vol % H 2 and 20 vol % N 2 mix to simulate reformate gas. We also performed a load cycling test with H 2 as anode gas. The results indicated that degradation rate of pure H 2 start–stop cycling showed 306 μ V h−1, while load cycling demonstrated a degradation rate of 19.7 μ V h−1 for the current density of 0.2 A cm−2, and 88.2 μ V h−1 for the current density of 0.4 A cm−2. Start–stop cycling with diluted gas resulted in a constant voltage drop with a degradation rate of 3.129 mV h−1. Electrochemical impedance spectroscopy (EIS) indicated an increased ohmic resistance during start–stop cycling and higher charge transfer (high-frequency) and mass transport (low-frequency) resistance with nitrogen introduction. Scanning electron microscope results confirmed MEA degradation. In conclusion, start–stop cycling and anode gas dilution are stressors that accelerate HT-PEM fuel cell degradation, reducing its lifetime. • Start–stop and anode gas dilution degrade HT-PEM cells. • Degradation jumps from 306 μ V/h to 3.129 mV/h with dilution. • Low degradation (88.2 μ V/h) at 0.4 A/cm² under load cycling. • Anode dilution with nitrogen amplifies resistive effects. • SEM analysis confirmed physical degradation of MEA. [ABSTRACT FROM AUTHOR]

One of the challenges of storing hydrogen in saline aquifers is the possible geochemical reactions between host rock, formation solution, and hydrogen. This study investigated the effect of hydrogen treatment on the mechanical properties of sandstone samples from Hulett member of Sundance Formation, a potential underground hydrogen storage host in Wyoming, USA. Cylindrical specimens were treated with brine, brine+50%H 2, and brine+100%H 2 for two weeks at a pressure of 15 MPa and a temperature of 83 °C. X-ray diffraction (XRD), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), uniaxial compression, and triaxial compression tests were conducted on specimens. Results showed that specimens treated with brine+50%H 2 and brine+100%H 2 , on average, exhibited 24 and 41% lower peak strength, respectively, compared to that of specimens treated with the brine. XRD results showed a decrease in dolomite and clay content of specimens after exposure to hydrogen, causing degradation of the mechanical and elastic properties of the specimens. • The effect of hydrogen on the mechanical properties of Hulett sandstone was investigated. • Dolomite and clay dissolution was observed after the treatment with hydrogen. • Specimens treated with hydrogen on average showed 41% lower strength. • An average 43% decrease in elastic modulus was observed after hydrogen treatment. [ABSTRACT FROM AUTHOR]

In order to study the effects of notched parameters on the hydrogen embrittlement (HE) behaviors of pipeline steel in hydrogen-blended natural gas environments, the mechanical properties of notched X80 steel specimens with various depth (δ), angle (ω) and curvature radius (ρ) were studied using slow strain rate tensile (SSRT) tests combined with scanning electron microscope (SEM) and finite element analysis (FEA). The tests indicate that the presence of notches greatly reduces the fracture strain, and increases the sensitivity of the specimen to HE. The geometric shape of the notch greatly affects the HE sensitivity of the notch specimen. The sharper the geometric shape of the notch, the higher the hydrostatic stress at the notch root, and the higher the diffusion hydrogen concentration, thereby increasing the hydrogen embrittlement sensitivity of the specimen. In addition, specimen with shallow notches also exhibits high hydrogen embrittlement sensitivity due to its shorter hydrogen atom diffusion distance. • The sharper the notch geometry, the higher the hydrogen embrittlement sensitivity. • The shallower the notch, the easier hydrogen atoms accumulate at the notch root. • The hydrostatic stress distribution affects hydrogen concentration distribution. • The lower stress concentration, the lower hydrogen embrittlement sensitivity. [ABSTRACT FROM AUTHOR]

Developing novel solid oxide fuel cells (SOFCs) with high stability running at low temperatures is an important objective in SOFC science. In the current paper, a comprehensive physics-based microstructure modeling using scanning electron microscope (SEM) image analysis was performed on several anode-support SOFCs operating at low temperatures with high stability. To bridge the gap in the literature regarding an accurate and realistic modeling, a new model was developed based on the variable fuel and air utilization factors and updated microstructure values (e.g., tortuosity, porosity, pore size, grain size). The model accuracy was verified by a thorough point-to-point validation for eight different cells with the configuration of Ni-YSZ (anode), YSZ (electrolyte), and GDC/PNO (cathode). Different temperatures, hydrogen, and air mass flow rates were used, for which an average error of less than 3% in the I-V curves was achieved. The microstructure of the cells, including cathode thickness (15–26 μm), anode-support thickness (350–460 μm), porosity (39 and 43%), grain size (1.1–1.4 μm), and pore radius (0.9–1.1 μm) were varied. Moreover, the effects of the critical operational and design parameters on the overpotential losses and cell performance were studied. The results show that a hydrogen flow rate of 43 sccm was ideal when the cell operated at 0.9 A/cm2 and 700 °C. Moreover, an average anode-support pore radius of 1.75 μm resulted in the best cell performance. It was also concluded that the electrolyte thickness has a higher effect on the cell performance compared to the cathode thickness. • Fabrication and testing of eight anode-supported tublar cells with different microstructures. • Introducing a physics-based microstructure model for SOFC based on variable fuel utilization factor. • Performing a comprehensive SEM image analysis for the fabricated cells. • Achieving an average error of less than 3% for the model compared to the experimental data. • Achieving an average optimum value of 1.75 μm for anode-support pore radius. [ABSTRACT FROM AUTHOR]

To meet the required useful life targets of proton exchange membrane fuel cells (PEMFC) for long haul and heavy-duty applications, the degradation mechanisms and influences from production need to be analyzed and reduced. Therefore, new and aged PEMFCs should be examined on a macro- and microscopic scale. The purpose of this work is to analyze fuel cells from series production and compare the findings with literature. Since most of the results from literature base on laboratory cells, this research closes the gap between lab-scale experiments and large-scale production. Thereto, the bipolar plates and membrane electrode assemblies of the fuel cells of the Toyota Mirai II and the Hyundai Nexo fuel cell vehicles were examined using optical and scanning electron microscopes. Additionally, energy-dispersive X-ray spectroscopy was performed. Differences in flow fields (channel dimensions, water management), layer and membrane thicknesses, surface porosities, contact angels and layer surface conditions were investigated. Comparisons with current literature provide an opportunity to estimate the influences of the observed structures. In addition, a methodology is developed to map temperatures that result in the discoloration of the titanium bipolar plates during abusive operation. [Display omitted] • Ex-Situ preparation of MEA and BPP of fuel cells from Toyota Mirai II and Hyundai Nexo. • Measurement of layer thickness and contact angles by optical microscopy. • Cracks found by surface analyses facilitate estimations of operating conditions. • SEM-EDX analyses show materials and distribution across a cell of Toyota Mirai II. • Post-mortem analyses of bipolar plate with thermal discoloration after abuse testing. [ABSTRACT FROM AUTHOR]

In proton exchange membrane water electrolysis system, higher hydrogen production rate, as well as medical-grade ozone generation is obtained if the applied voltage is increased from 2.0 V to 3.5 V. However, this also leads to harsh conditions encountered by both anode and anode support of membrane electrode assembly. For example, Ti plate as anode support, needs coating to prevent corrosion and to stabilize operation. In this study, commercial Ti plates are polished with sand papers of different degree of roughness before electrocoating. The characteristics of the coated Ti anode support are determined by field-emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDS), electrochemical impedance spectroscopy (EIS), and electrolyzer test. In conclusion, the performance of coated Ti anode support improved with polish, reach a maximum and then decrease with highest degree roughness. • Polishing metallic anode plate surface reduces the ICR. • Optimal roughness of metallic anode plate is beneficial for anti-corrosion materials attachment. • Anti-corrosion materials attachment lead to stable PEMWE performance. • Ti plate polished with P1200 sand paper gives optimum performance in PEMWE. [ABSTRACT FROM AUTHOR]

The influence of Na 2 MoO 4 concentration on the electrochemical deposition of Co–Fe and Co–Fe–Mo alloy coatings from slightly acidic citrate baths and their electrocatalytic performance for alkaline water electrolysis in 1 M NaOH solution have been examined. The chemical composition and the evolution of the crystallographic structure have been analyzed by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), and scanning electron microscope with energy dispersive spectroscopy (SEM-EDS) measurements. Increasing concentration of Mo in the alloy led to gradual amorphization of the crystalline structure. Electrochemical studies revealed that the cathodic Tafel slope reduced to 69 mV/dec for Co–Fe–Mo alloys. Furthermore, a low overpotential value of −121 mV was observed from polarization studies, which confirmed a good catalytic activity for the alkaline water splitting process. • Co–Fe and as Co–Fe–Mo ternary alloys, were fabricated on a copper electrode at different conditions. • Addition of Mo into alloy led to amorphization of the crystalline structure and decrease the overpotential value. • The enhanced activity of Co 57 Fe 24 Mo 19 ternary alloy is related to the synergetic effects between elements. [ABSTRACT FROM AUTHOR]

A series of Co–Ce–Al–O mesoporous catalysts synthesised by self-assembly is shown to be efficient for the hydrogen production via ammonia decomposition reaction. The evaporation-induced self-assembly method is utilised to effectively synthesise mesoporous multicomponent catalysts with tuned composition and improved performance. The prepared catalyst materials were characterised by several techniques including X-ray diffraction, scanning electron microscope, transmission electron microscope and N 2 physisorption analysis. The kinetic performance of the solid catalysts was evaluated at different temperatures and flow rates under atmospheric pressure. The optimised Co 0.5 Ce 0.1 Al 0.4 O(sa) catalyst remained highly active below 550 °C which represents a competitive performance among state-of-the-art catalysts. The promising performance of the catalyst and the use of nonprecious metals in the structure represent a feasible approach towards the application of ammonia as a hydrogen carrier for on-board hydrogen production. [Display omitted] • The Co–Ce–Al–O mesoporous catalyst is prepared using a self-assembly method for ammonia decomposition. • Ammonia conversion of 98% was obtained at 550 °C with the GHSV of 12,000 mL h−1 g cat −1. • Cerium promoted the catalyst activity, and aluminium enhanced the catalyst stability. • The Co–Ce–Al–O catalytic performance is comparable to Ru-based catalysts. [ABSTRACT FROM AUTHOR]

In this study, the different kinds of fluorides (NiF 2 , CrF 2 , and ZrF 4) are combined with the carbonaceous catalyst Co@C to explore their co-catalytic effect on the Mg–Al–Y-based hydrogen storage material. The obtained composites are named as Mg 91 Al 5 Y 4 -5 wt.%TmF x (TmF x = NiF 2 , CrF 2 and ZrF 4)-5 wt.%Co@C. The isothermal and non-isothermal hydrogen storage properties of the composites were measured by Sievert apparatus and differential scanning calorimeter, respectively. X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) were used for characterizing the phase component and observing microtopography. To make sense of the action mechanism of fluorides, the MgH 2 supercell was established to study the occupation of F and Ni atoms and the first-principle pseudopotential plane wave method was utilized to calculate the heat of formation (Δ H sys) of these systems and the dissociation energy (Δ E) of single H atom. According to the results, the Mg 91 Al 5 Y 4 -5 wt.%NiF 2 -5 wt.%Co@C specimen has the minimal enthalpy change of hydrogen evolution (75.7 kJ/mol H 2) and activation energy of dehydrogenation (81.4 ± 1.09 kJ/mol), showing the optimal hydrogen storage performances. The calculation results are consistent with the experiments that the introduction of Ni leads to the decline in Δ H sys and Δ E , suggesting the destabilization of MgH 2 and the enhancement of dehydrogenation. The F atom occupying H or the gap position will lead to the increase of Δ H sys and induce the system to be more stable. [Display omitted] • Fluorides and porous layered carbon co-catalyze Mg–Al–Y hydrogen storage alloy. • Carbon-based catalyst improves ball milling efficiency and modifies alloy surface. • Adding NiF 2 introduces hydrogen pumping effect by forming Mg 2 NiH 4. • Ni and F atoms entering the MgH 2 lattice contributes to hydrogen dissociation. • The combination of NiF 2 and carbonaceous material produces the best catalytic effect. [ABSTRACT FROM AUTHOR]