Study of the composition and structure of ion-conducting membranes based on polyvinyl alcohol by 1H NMR spectroscopy

One of the alternative types of proton-conducting membranes for a hydrogen-air solid polymer fuel cell is the type of hybrid membranes based on polyvinyl alcohol (PVA) crosslinked with aldehyde, modified by sulfonic acid. Earlier, for the first time, we obtained new ion – conducting membranes based on furfural-crosslinked PVA modified aminosulfonic acid (ASA) and tetraethoxysilane (TEOS), as well as membranes not crosslinked with furfural (FUR) or unmodified ASA and TEOS, by a liquid-phase synthesis method, in an organic medium-dimethyl sulfoxide. The values of their ionic conductivity and the degree of swelling in water are presented. In this work, the composition and structure of the obtained ion-conducting membranes are studied using liquid-phase nuclear magnetic resonance (NMR) spectroscopy on ¹H nuclei. In the ¹H NMR spectrum of an ion – conducting membrane not cross-linked with the «PVA/ASA», the signal of free OH groups of PVA is observed to disappear, but at the same time a characteristic triplet at 7.1 ppm. is preserved, having a constant of ～51 Hz and components of the same intensity (1:1:1), which corresponds to protons of ¹⁴NH₄⁺ hydrolyzed ASA. The disappearance of the expanded signal at 9.6 m. d. of protons of the free sulfo group of ASA and a narrow singlet signal at 5.8 m. d. of free protons of the NH₂ group of ASA indicates the interaction of ASA with OH groups of PVA. In the ¹H NMR spectrum of an ion – conducting membrane crosslinked with FUR – «PVA/ASA/FUR», signals of protons of the furan ring of FUR and a signal of its aldehyde group are observed, which is shifted to a strong field, which is determined by the formation of a chemical bond between FUR and the polymer chain of PVA. In the ¹H NMR spectra of all membranes modified by ASA, the appearance of a second weaker-field ¹⁴NH₄⁺ triplet is observed, and in the spectra of a number of ion – conducting hybrid membranes modified by TEOS – «PVA/ASA/FUR/TEOS», signals of the third type of ¹⁴NH₄⁺ triplets shifted in a strong field relative to the other two ¹⁴NH₄⁺ triplets were detected. The appearance of additional ¹⁴NH₄⁺ triplets indicates the formation of several bound forms of the ammonium ion.     

Dynamic modelling of PEM fuel cell system for simulation and sizing of marine power systems

This article presents a model of a proton exchange membrane fuel cell (PEMFC) system for marine power systems. PEMFC in marine hybrid power sources can have various power ranges and capacities in contrast with vehicle applications. Investigating PEMFCs behaviour and performance for various conditions and configurations is demanded for proper sizing and feasibility studies. Hence, modelling and simulation facilitate understanding the performance of the PEMFC behaviour with various sizes and configurations in power systems. The developed model in this work has a system level fidelity with real time capabilities, which can be utilized for simulator approaches besides quasi-static studies with a power-efficiency curve. Moreover, the model can be used for scaling the PEMFC power range by considering transient responses and corresponding efficiencies. The Bond graph approach as a multi-disciplinary energy based modelling strategy is employed for the PEMFC as a multi domains system. In the end, various PEMFC cell numbers and compressor sizes have been compared with power-efficiency curves and transient responses in a benchmark.     

U.S. regulatory perspectives on the back end of the fuel cycle: EUROSAFE 2013 proceeding

For the United States Nuclear Regulatory Commission and the reactor licensees it regulates, there are a number of contemporary issues associated with the back end of the fuel cycle including, the agency's revision to its “Waste Confidence” decision and the path-forward for high-level waste disposal. Additionally, the 2012 Blue Ribbon Commission on America's Nuclear Future recommendations, the future of reprocessing, consolidated interim spent fuel storage, and maintaining technical competence within the NRC in challenging budgetary conditions are addressed. I conclude that there is confidence in the feasibility of safe storage of spent nuclear fuel following the licensed operational life of a reactor and any change in high-level waste policy will require Congressional action to amend the Nuclear Waste Policy Act.     

Feasibility assessment of a container ship applying ammonia cracker-integrated solid oxide fuel cell technology

The maritime industry has entered its pathway of decarbonization. To achieve the IMO's ambitious goals of an absolute emissions reduction of 50% by 2050, and a 70% carbon intensity reduction by 2050 compared to the 2008 level, various options for the adoption of technologies and alternative fuels are considered by the market stakeholders.Ammonia, one of the most promising alternative marine fuels has long been considered to reduce carbon emissions. And solid oxide fuel cell is expected to transform ship propulsion technology in the future due to its high utilization of fuels. In this paper, a feasibility study is performed to assess the application of an ammonia cracker-integrated solid oxide fuel cell (hereafter as Ammonia SOFC) system on an ocean-going vessel through a detailed CAPEX, FuelEX, OPEX, Carbon tax, and carbon emission analysis. Comparison is made with direct ammonia, LNG and conventional fuels fired heat engines. The result concludes that it can be economically viable to apply to deep-sea shipping, compared to other marine fuels and propulsion technologies.     

Tape casting coupled with isostatic pressing as an alternative fabrication method for microtubular solid oxide fuel cells

A new production technique consisting mainly of a combination of tape casting and isostatic pressing to fabricate microtubular supports for solid oxide fuel cells is presented in this study. For this purpose, thin anode support layer is obtained by tape casting. The tape is then wrapped around a rod and subjected to isostatic pressing. The anode support microtube laminate is sintered after the removal of the rod. Microstructural observations show that the anode support with the suggested method is free of delamination and structural defect. Similar microtubular supports are also fabricated by conventional extrusion to compare the mechanical performance. Three point bending test results indicate that the anode supports with the suggested method provide higher mechanical strength due to improved compaction by isostatic pressing. Furthermore, similar microtubular cells are constructed on both anode supports for the electrochemical considerations. The results reveal that the cell, whose anode support is manufactured via tape casting and isostatic pressing, provides a reasonable electrochemical performance although no optimization is carried out in the fabrication steps. Therefore, the method recommended in this study is found to be an appropriate method for the fabrication of tubular/microtubular supports in solid oxide fuel cells or in similar areas.     

Microstructure and electrical conductivity of La0.9Sr0.1 Ga0.8Mg0.2O2.85-Ce0.8Gd0.2O1.9 composite electrolytes for SOFCs

(100-x) wt.% La_0.9Sr_0.1 Ga_0.8Mg_0.2O_2.85 - x wt.% Ce_0.8Gd_0.2O_1.9 (x = 0, 5, 10, 20) electrolytes were prepared by solid-state reaction. The composition, microstructure, and electrical conductivity of the samples were investigated. At 300 ~ 600°C, the pure La_0.9Sr_0.1 Ga_0.8Mg_0.2O_2.85 electrolyte has a higher conductivity compared to the composite electrolytes, but at 650 ~ 800°C the 95 wt.% La_0.9Sr_0.1 Ga_0.8Mg_0.2O_2.85 - 5 wt.% Ce_0.8Gd_0.2O_1.9 composite electrolyte presents the highest conductivity, reaching 0.035 S cm⁻¹ at 800°C. The cell performances based on La_0.9Sr_0.1 Ga_0.8Mg_0.2O_2.85-Ce_0.8Gd_0.2O_1.9 electrolytes were measured using Sr₂CoMoO₆-La_0.9Sr_0.1 Ga_0.8Mg_0.2O_2.85 as anode and Sr₂Co_0.9Mn_0.1NbO₆ -La_0.9Sr_0.1 Ga_0.8Mg_0.2O_2.85 as cathode, respectively. At 800°C, the measured open-circuit voltages are higher than 1.08 V, and the maximum power density and current density of the fuel cell prepared with 95 wt.% La_0.9Sr_0.1 Ga_0.8Mg_0.2O_2.85 - 5 wt.% Ce_0.8Gd_0.2O_1.9 electrolyte reach 192 mW cm⁻² and 720 mA cm⁻², respectively.     

Modified La0.6Sr0.4Co0.2Fe0.8O3-δ cathodes with the infiltration of Er0.4Bi1.6O3 for intermediate-temperature solid oxide fuel cells

Aiming to lower the activation energy and expedite the oxygen reduction reaction (ORR) process of La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) cathodes for application in intermediate-temperature solid oxide fuel cells (IT-SOFCs), Er_0.4Bi_1.6O₃ (ESB) modified LSCF was prepared by infiltrating using organic solvents. The infiltration of ESB dramatically reduces the polarization resistances of LSCF cathodes (from 0.27 to 0.11 Ω cm² at 700 °C, from 0.58 to 0.25 Ω cm² at 650 °C), and lowers their activation energy (from 100.28 to 97.15 kJ mol^?1). Also, ESB makes the rate-limiting step of LSCF cathodes at high frequency change from the charge transfer process on the cathode to the adsorption and diffusion of oxygen on cathode surface. The single cell with ESB infiltrated LSCF cathodes shows a peak power density of 469 mW cm^?2 at 700 °C using humid hydrogen and air as fuels and oxidants, respectively, as well as a good short-term stability for 50 h.     

Degradation rate quantification of solid oxide fuel cell performance with and without Al2TiO5 addition

Degradation rates of electrical current during constant voltage operation of SOFCs with anodes made using NiO precursor powders from two different manufacturers with and without the addition of aluminum titanate (ALT) added by either mechanical mixing or anode infiltration have been quantified using a novel MATLAB algorithm. Because the algorithm has been used to quantify degradation rates for many different SOFC tests, it is thought that the method can be applied to most measured SOFC data to quantify the instantaneous cell degradation rate as a function of time for the entire SOFC performance measurement. Degradation rates determined at different times have been plotted against varying concentrations of ALT addition, facilitating the estimation of optimum ALT concentration for SOFC anodes made with NiO from a specific manufacturer. The algorithm used to determine degradation rates is available upon request to the corresponding author.