Hydrogen Permeation Measurements Research Articles

Enhancing Durability of Polymer Electrolyte Membrane Water Electrolyzer through Incorporation of Gas Recombination Catalyst in Membrane

Hydrogen will become a critical component of the future energy landscape driven primarily by the growing use of renewable energy sources. Polymer electrolyte membrane water electrolyzer (PEMWE) is a superior technology to facilitate hydrogen production from renewable electricity. However, durability remains a significant challenge for the widespread commercialization of electrolyzers.1 Cross-over of H2 from cathode to anode could lead to explosive mixtures in the anode causing safety concerns during operation. Hydrogen crossover also impacts the durability of the anode catalyst.2 Hydrogen permeation from the cathode to the anode through the membrane reduces the anodic Ir catalyst to a low valence state leading to increased dissolution of the Ir catalyst at a high cell voltage. Utilizing thin membranes (~50µm) can improve the electrolyzer system’s efficiency but also increase the hydrogen permeation, particularly at high pressures.In this study, we present a methodology to incorporate platinum as a gas recombination catalyst (GRC) layer into commercial membranes, significantly reducing hydrogen permeation rates and mitigating anode catalyst degradation. Membranes with GRC can mitigate the degradation of PEMWE, leading to more efficient and durable PEM electrolysis systems for hydrogen production. The methodology developed enables higher control of the GRC layer properties (Pt particle size and location in the membrane). Ex-situ measurement of hydrogen permeation, shown in Figure 1, indicates a significant reduction in the permeation rate for GRC incorporated NR 212. This study presents a systematic electrochemical evaluation of anode degradation in PEMWE with and without GRC in the membrane using accelerated stress tests. The durability of the GRC during long-term operation is also presented. Acknowledgment This research is supported by the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office through the Hydrogen from Next-generation Electrolyzers of Water (H2NEW) consortium.

Influence of metallurgical factors on the hydrogen induced cracking of carbon steel wires in H2S-containing environments

Flexible pipes armor wires used in offshore oil and gas fields can corrode if water and acid gases, such as H2S, build up in the annulus. Such an environment may provide the conditions for hydrogen-induced cracking (HIC) depending on the corrosive solution composition and the metallurgical characteristics of the armor wire, such as microstructure and microhardness. The critical zones of HIC incidence were investigated for tensile and pressure armor wires with carbon content of 0.7 and 0.3 wt% C, respectively. Results were obtained through immersion testing and hydrogen permeation measurements in near neutral substitute ocean water (solution A) and standard acid solution (solution B) at ambient temperature bubbled with a gas mixture (1 % H2S + 99 % N2). Scanning electron microscope (SEM) and computed tomography (CT) evidenced the microstructure and microhardness features associated to crack morphology and location. According to the results, the increase of carbon content in cold drawn steels promoted the accumulation of hydrogen mainly in regions of high microhardness, inducing a high density of cracks in a stepwise cracking (SWC) propagation. This indicates that the driving force for HIC was associated with metallurgical factors, such as microhardness, the presence of hydrogen trapping sites of high energy, dislocations and ferrite/cementite morphology and distribution, occurring even in the absence of non-metallic inclusions. Additionally, environmental conditions, such as the low pH found in solution B, increased the criticality of HIC. Both materials presented a crack sensitivity ratio (CSR) that grew over time in solution B, but no cracks were observed in the pressure armor wire tested in solution A. Hydrogen permeation curves were delayed for both tested armor wires in solution A due to its near neutral pH characteristic. Hydrogen diffusivity (Deff) of the tensile armor wire was lower than the pressure armor wire, indicating the presence of a higher density of hydrogen trapping sites in a harder and elongated pearlite.

Influence of Frictional Heat on Hydrogen Permeation Measurements

Hydrogen transport properties in metals are often investigated in electrochemical Devanathan-Stachurski double cells (DS) or modifications thereof. A DS setup consists of input and output cells which are divided by a metal membrane. The hydrogen oxidation current measured in the output cell is proportional to the permeation rate of hydrogen through the metal membrane. In certain applications of lubricated tribocontacts, steel is susceptible to damages by uptake of hydrogen. For investigation of the friction-generated hydrogen uptake a lubricated sliding contact in the input cell of the DS setup is realized.Related low hydrogen permeation current signals are significantly affected by the steel membrane temperature. As an example, frictional heating of the steel membrane leads to additional release of residual hydrogen from the steel. To investigate the temperature effect, tests with an oil containing a hydrogen promotor, a PFPE oil and without lubrication were conducted. The results indicate that the permeation signal is strongly influenced by frictional heating. Such measured currents must not be misinterpreted as hydrogen generated by lubricants. A thermodynamic and kinetic model of the hydrogen diffusion and trapping reveals the correlation between current signal and temperature change.

Temperature effects in hydrogen permeation measurements under lubricated sliding conditions

Under specific conditions, steel in lubricated tribocontacts of bearings is susceptible to hydrogen related damages. Several works attempted to measure hydrogen from friction induced degradation of lubricants and its permeation through steel membranes in modified Devanathan-Stachurski cells. This article discusses the temperature effect on the measured current. Comparison of the results from an oil with a hydrogen source, a PFPE oil and without lubrication indicates that the current is strongly influenced by frictional heating. Such measured currents should not be misinterpreted as release of hydrogen by lubricants. A mathematical model of diffusion and trapping of atomic hydrogen qualitatively explains the temperature effect. Comparison between experimental and simulation results suggests a causal relationship between membrane temperature and permeation current signal.

Effect of thin films coated steel membrane on electrochemical hydrogen permeation measurement: Palladium vs. nickel

The effects of thin films plated on steel membranes on the electrochemical hydrogen permeation behaviors were examined using the hydrogen permeation transients of two coating materials, Pd and Ni, with varying thicknesses. The complete Ni film plated on a steel membrane can be preferable over a complete Pd film in that there is no dependence on the film thickness for measuring the hydrogen oxidation rates in anodic side of the permeation experiment. By contrast, the increase in thickness of the Pd film resulted in much slower oxidation kinetics, which may have resulted from the slower diffusion of atomic hydrogen through the film by the hydrogen trapping at any lattice defects in the film, delaying hydrogen transport. Nevertheless, the use of Ni film has a drawback in that the time required to reach a background current density was longer due presumably to its lower electrochemical stability under a high anodic potential.

Enhanced Proton Conduction with Low Oxygen Vacancy Concentration and Favorable Hydration for Protonic Ceramic Fuel Cells Cathode

Protonic ceramic fuel cells (PCFCs), as an efficient energy storage and conversion device, have great potential to solve the serious problems of energy shortage and environmental pollution. Improving the proton conductivity of the promising cathode materials is an effective solution to promote the widespread application of PCFCs at low temperatures (450-650 °C). Herein, considering the high oxygen reduction reaction (ORR) activity of BaCoO3-based perovskite oxide and beneficial proton uptake capacity of Zn-doping, we construct BaCo0.4Fe0.4Zn0.1Y0.1O3-δ (BCFZnY) as the PCFCs cathode, and compare it with the classic triple-conducting cathode BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZrY). Different from the general strategy of increasing the initial oxygen vacancy concentration of cathode materials, this work unveils that enhancing the hydration of perovskite oxide with low oxygen vacancy concentration is a more effective strategy to accelerate the proton diffusion in the electrode. Therefore, the BCFZnY cathode achieved excellent proton conductivities of 8.05 × 10-3 and 6.38 × 10-3 S cm-1 as obtained by hydrogen permeation measurements and peak power densities of 982 and 320 mW cm-2 in a BaZr0.1Ce0.7Y0.1Yb0.1O3-δ-based anode-supported fuel cell at 600 and 450 °C, respectively.

Direct observation of hydrogen permeation through grain boundaries in tungsten

In this paper, we report on an enhanced hydrogen permeation effect along grain boundaries in tungsten. Sputtered nanocolumnar tungsten layers (column lateral dimensions 100–150 nm and layer thickness 2 μm) were analysed by hydrogen permeation measurements in the temperature range 520–705 K. The experiments constitute a direct observation of this effect, previously postulated by means of a combination of indirect experiments and simulations and considered controversial due to the lack of direct measurements. DFT results support this observation since (i) the hydrogen binding energy to the grain boundary is 1.05 eV and (ii) the migration energies along the grain boundary and along the bulk are 0.12 eV and 0.20 eV, respectively. OKMC simulations, parametrized by DFT data, were used as a supporting tool to attain a better understanding of the involved phenomena. The OKMC results are also compatible with the observations. Indeed, they show that the fraction of hydrogen flux along grain boundaries in the steady-state permeation regime increases when decreasing the ratio of lateral dimensions to length of the nanocolumns, rapidly approaching unity when this ratio is < 2. Therefore, grain boundaries act as preferential migration pathways for H atoms at the studied temperature range in the studied samples. This behaviour has interesting implications to reduce the retention of hydrogen in several applications, in particular, fusion materials exposed to plasma discharges.

A Quantified Study of the Resistance of Duplex Stainless Steels to HISC: Part 1–Significance of the Three-Dimensional Phase Distributions and Morphological Properties on Hydrogen Transport

This paper is associated with a larger program of research, studying the resistance to hydrogen-induced stress cracking (HISC) of a wrought and a hot isostatically pressed UNS S31803 duplex stainless steel (DSS), with respect to both the independent and interactive effects of the three key components of HISC: microstructure, stress/strain, and hydrogen. In the first part presented here, several material properties such as the three-dimensional microstructure, distribution, and morphology/geometry of the two phases, i.e., ferrite and austenite, and their significance on hydrogen transport have been determined quantitatively, using x-ray computed tomography microstructural data analysis and modeling. This provided a foundation for the study to compare resistance to HISC initiation and propagation of the two DSSs with differing microstructures, using hydrogen permeation measurements, environmental fracture toughness testing of single-edge notched bend test specimens, in Part 2 paper of this study (Blanchard, et al., Corrosion 78, 3 [2022]: p. 258–265).

A Quantified Study of the Resistance of Duplex Stainless Steels to HISC: Part 2–Significance of the Hydrogen Permeation Properties and Severity of Stress Raisers on Hydrogen Transport and Cracking

The quantified microstructural analysis performed on a wrought and a hot isostatically pressed UNS S31803 duplex stainless steel (DSS) in the Part 1 publication of this study established the significance of the three-dimensional (3D) distribution and morphology/geometry of the ferrite and austenite phases on hydrogen transport through two DSS product forms (see Blanchard, et al., Corrosion 78, 3 [2022]: p. 249–257). This paper is a follow-up to Part 1 and focuses on the role of the other two key, interrelated components of hydrogen-induced stress cracking (HISC): stress/strain and hydrogen. For this purpose, experimental hydrogen permeation measurements, and environmental fracture toughness testing (i.e., J R-curve testing) using conventional and nonstandard single-edge notched bend test specimens were used. These particularly enabled interpretation of the hydrogen permeation and transport test data, and evaluation of suitability of environmental fracture toughness test methods for the assessment of resistance to HISC in DSSs. The latter is discussed, both from laboratory and component integrity perspectives, in the context of the findings from the 3D microstructural characterization of the two phases, the role of stress raisers and their severity, and hydrogen transport through the bulk and from the surface.

Hydrogen permeation from F82H wall of ceramic breeder pebble bed: The effect of surface corrosion

Understanding the permeation behavior of tritium from a pebble bed breeding blanket is essential for establishing a self-sufficient fuel cycle in a nuclear fusion reactor. It is known that double corrosion layers forms on reduced activation ferritic-martensitic (RAFM) steel surface by gas release from a ceramic breeder material, however, its effect on hydrogen permeation behavior has not been elucidated. Herein, in-situ measurement of hydrogen permeation through an F82H RAFM wall of a ceramic breeder pebble bed was performed under H2-added sweep gas conditions. The corrosion layer formed on the F82H sample had a dense microstructure, which reduced hydrogen permeation flux at least by one order of magnitude. The permeation reduction factors were 20–50 at the water-coolant temperature of a blanket. A self-repairing ability is expected for the surface oxide layer as the corrosion occurs spontaneously inside a breeding blanket.

Proposal of Diffusion Model Obtained from Time-resolved Hydrogen Permeation Measurement with Operando Hydrogen Microscopes

Proposal of Diffusion Model Obtained from Time-resolved Hydrogen Permeation Measurement with Operando Hydrogen Microscopes

Evaluation of Transport Properties of Lanthanum-Based Proton-Conducting Composite Electrolytes

For efficient energy conversion and energy storage, developing highly efficient hydrogen permeable membranes is a crucial issue. Ceramic hydrogen permeable membranes, i.e., protonic electronic mixed conductors, work on bipolar transport of protons and electrons. Ceramic composite membranes meet this requirement with chemical and thermal stability, and they can be used not only as hydrogen permeable membranes but also as electrolytes in protonic ceramic fuel cells (PCFCs). Although improvement in protonic conductivity at heterointerfaces between constituting materials and/or space-charge relaxation around the resistive grain boundaries can be possible origins of the enhanced hydrogen permeability in the composite electrolyte membranes, its detailed mechanisms have not been clarified yet and the strategy of material design for composite membranes has not been established. In this study, the transport properties of composite electrolyte membranes consisting of protonic conductors and electronic conductors are investigated to realize highly efficient PCFC operating at low temperatures and to clarify the principles of carrier transport in the composite membranes. For the protonic conductor and the electronic conductor, we selected La2Ce2O7 (LDC) with a fluorite structure and La0.3Sr0.6TiO3 (LST) with a perovskite structure, respectively. The composite membrane composed of LDC and LST (LDC/LST) with various LDC to LST ratios was prepared by a solid-state reaction. Phase stability of LDC and LST were investigated by X-ray diffraction (XRD) measurements. Transport properties of hydrogen permeation cells using the LDC-LST composite membranes with Pt electrodes were assessed by electrochemical impedance spectroscopy (EIS) measurements and hydrogen permeation measurements. Hydrogen fluxes were measured by gas chromatography. The EIS measurements revealed that the grain-boundary resistance was reduced for the LDC/LST composite membrane in comparison with an LDC membrane. In particular, LDC/LST (weight ratio 1:2) showed the smallest grain-boundary resistance of 26 Ω cm at 600°C under 1%H2/Ar among the measured samples. Besides, the hydrogen permeation measurement showed that LDC/LST exhibited higher hydrogen permeability than the LDC membrane. In addition, the hydrogen flux of LDC/LST (1:2) was almost twice as high as that of LDC at 600°C. The low grain-boundary resistance and the high hydrogen permeability of LDC/LST composite membrane suggests that the introduction of LST accelerates the proton conduction in the membrane.

Photolithographic Fabrication of a Micro-electrode Surface on a Carbon Steel Sheet for Local Hydrogen Permeation Measurements

Photolithographic Fabrication of a Micro-electrode Surface on a Carbon Steel Sheet for Local Hydrogen Permeation Measurements

Insight into elevated temperature and thin membrane application for high efficiency in polymer electrolyte water electrolysis

We present a study of a liquid water fed polymer electrolyte water electrolyzer (PEWE) at cell temperatures of up to 120 °C using thin membranes of 50 µm thickness. Further, we show that under these conditions conversion efficiency increases by up to 14% at 3 A cm−2 in comparison to today's state of the art (60 °C, 180 μm membrane). Alternatively, an increase of the current density by a factor of 3 at an efficiency of 75% is possible. A detailed voltage loss analysis is provided that helps to understand to which extent the overpotential contributions are reduced. From hydrogen permeation measurements, we determine faradic efficiency and the safety limits of cell operation revealing that operating temperatures higher than 100 °C with thin membranes are not possible at current densities lower than 0.8 A cm−2 due to the safety limit of 2% hydrogen in oxygen in the anode compartment. The decrease in overpotential allows to significantly reduce the energy requirement or to increase the production rate of hydrogen. The results can help to benchmark future efficiency targets and points towards next generation PEWE materials and components to further reduce loss contributions.

Improved Stress Corrosion Cracking Resistance of High‐Strength Low‐Alloy Steel in a Simulated Deep‐Sea Environment via Nb Microalloying

Microstructure observations, thermal desorption spectroscopy (TDS) tests, hydrogen permeation measurements, electrochemical tests, and slow strain rate tensile (SSRT) tests are conducted investigate the beneficial effect of Nb microalloying on the stress corrosion cracking (SCC) behavior of high‐strength low‐alloy (HSLA) steels in a simulated deep‐sea environment. The results show that the addition of Nb significantly decreases the SCC susceptibility of HSLA steel in a simulated deep‐sea environment, and the role of Nb is attributed to microstructure optimization and the strong hydrogen‐trap function of nanosized NbC precipitates with hydrogen activation energy up to 100.5 kJ mol−1. In the simulated deep‐sea environment, the SCC resistance of HSLA steel is enhanced by microstructure optimization and the hydrogen‐trap function via Nb microalloying, and both anodic dissolution (AD) and hydrogen embrittlement (HE) are weakened. Moreover, the improvement of SCC resistance of HSLA steel with a higher hydrogen concentration via Nb microalloying is more obvious, in which the decrease of hydrogen‐induced anodic dissolution (HIAD) and HE effects is more distinct, and the strong hydrogen‐trap effect of NbC precipitates is the predominant mechanism to improve SCC resistance.

Hydrogen Diffusion and Its Effect on Hydrogen Embrittlement in DP Steels With Different Martensite Content

The hydrogen diffusion behavior and hydrogen embrittlement susceptibility of dual phase (DP) steels with different martensite content were investigated using the slow strain-rate tensile test and hydrogen permeation measurement. Results showed that a logarithmic relationship was established between the hydrogen embrittlement index (IHE) and the effective hydrogen diffusion coefficient (Deff). When the martensite content is low, ferrite/martensite interface behaves as the main trap that captures the hydrogen atoms. Also, when the Deff decreases, IHE increases with increasing martensite content. However, when the martensite content reaches approximately 68.3%, the martensite grains start to form a continuous network, Deff reaches a plateau and IHE continues to increase. This is mainly related to the reduction of carbon content in martensite and the length of ferrite/martensite interface, which promotes the diffusion of hydrogen atoms in martensite and the aggregation of hydrogen atoms at the ferrite/martensite interface. Finally, a model describing the mechanism of microstructure-driven hydrogen diffusion with different martensite distribution was established.

Elevated Temperature Proton Exchange Membrane Water Electrolysis for Reduced Cost of Green Hydrogen Production

Proton exchange membrane water electrolysis (PEMWE) is one of the most promising technologies for the production of green hydrogen through renewable energy sources [1]. A major obstacle of the technology to enter a large scale market is the high hydrogen production cost in comparison to traditional steam methane reforming (SMR). Recently, it has been shown that the capital expenditure (CAPEX) of PEMWE could be significantly reduced by application of new cell materials [2]. In order to further reduce the cost of green hydrogen it is necessary to reduce the operational expenditure (OPEX). On the one hand the OPEX is strongly driven by the electricity cost, on the other hand it can be reduced by increasing the efficiency of PEMWE [3].One possibility to do so it to increase the operating temperature. This makes water electrolysis thermodynamically more efficient but also reduces the cell’s loss contributions. Additionally, the usage of thin membranes would lower ohmic overpotentials. Industrial electrolysers are currently operated at around 60°C and use thick membranes of about 200µm. The more demanding conditions of elevated temperature operation and the use of thin membranes are a challenge for the chemical and mechanical stability of the electrodes and the membrane [4]. Moreover, they imply a major safety concern due to increase of hydrogen crossover. Anticipated materials are required to master the more challenging operation mode.In this study, we present a self-built test bench that allows to operate a PEMWE single cell of 25cm2 at temperatures of up to 120°C and use thin membranes of 60µm. By performing hydrogen permeation measurements, we are able to determine Faradic efficiency and the safety limits of PEMWE. Higher operating temperatures are not possible due to the safety limit of 2% hydrogen in oxygen in the anode compartment. A detailed cell loss analysis helps to understand to which extent the overpotential contributions can be reduced. Further, we show that with the advanced conditions the PEMWE efficiency increases by up to 14% at 3Acm-2 or an increase of the current density by 200% at an efficiency of 75% is possible (Figure 1a). The decrease in overpotential allows to significantly lower the electricity costs or to increase the production rate of hydrogen (Figure 1b).[1] U. Babic, M. Suermann, F.N. Büchi, L. Gubler, T.J. Schmidt, Critical Review—Identifying Critical Gaps for Polymer Electrolyte Water Electrolysis Development, Journal of The Electrochemical Society, 164 (2017) F387-F399.[2] K. Ayers, N. Danilovic, R. Ouimet, M. Carmo, B. Pivovar, M. Bornstein, Perspectives on low-temperature electrolysis and potential for renewable hydrogen at scale, Annual Review of Chemical and Biomolecular Engineering, 10 (2019) 219-239.[3] J. Proost, State-of-the art CAPEX data for water electrolysers, and their impact on renewable hydrogen price settings, International Journal of Hydrogen Energy, 44 (2019) 4406-4413.[4] C. Mittelsteadt, J. Willey, R. Stone, J. Riffle, J. Rowlett, A. Daryaei, J. McGrath, dings, US Department of Energy, Arlington, VA (USA), June 8-12, 2015 Figure 1

On a mechanism for enhanced hydrogen flux along grain boundaries in metals

Using X-ray diffraction, namely a rocking curve scan, the effect of electrolytic hydrogen charging on the crystal structure in the Fe-36Ni alloy has been studied in comparison with that after gaseous hydrogenation. It is shown that, in contrast to gaseous charging, the electrolytic one induces plastic deformation increasing thereby density of dislocations and causing crystallographic texture. Based on the analysis of available contradictory data on the grain boundary hydrogen diffusion during the measurements of hydrogen permeation and the obtained experimental data, it is proposed that enhanced hydrogen flux along the grain boundaries is due to hydrogen transport by moving dislocations.

The Effect of the Partial Pressure of H2S and CO2 on the Permeation of Hydrogen in Carbon Steel by Using Pressure Buildup Techniques

There are concerns in the industry about using an electrochemical technique for actual hydrogen permeation measurements where charging current is not a field condition. The objective of this work is to use pressure buildup techniques to study the influence of H2S and CO2 partial pressure on the relationship between hydrogen permeation and corrosion rate measured by different techniques. Sulfide films formed on carbon steel in a solution containing 5 wt% NaCl and 0.5 wt% acidic acid at various H2S and CO2 partial pressures were characterized, and the effect of the film on hydrogen permeation was also investigated. Field conditions were included in this study for comparison purposes. The relationship was modeled at the steady state of both hydrogen flux and corrosion rate. The results confirmed by use of two hydrogen flux measurement techniques (eudiometer and high-pressure buildup probe) and two corrosion measurement methods (weight loss coupons and coupled multiarray electrode system), that there is no direct correlation between hydrogen flux and corrosion rate. Therefore, the hydrogen permeation rate in H2S and CO2 environments was found to be more controlled by partial pressure of H2S than corrosion rate. The amount of descent in hydrogen flux, after reaching maximum of hydrogen permeation rate and before reaching a steady state, depends on the morphology and structure of corrosion films which are mainly controlled by concentration of H2S.

Comparative study of devices for hydrogen permeation measurements

New devices for measurement of hydrogen permeability in steels using electric resistance sensors have been assessed. Diffusion coefficients of two types of advanced high strength steels obtained with the traditional electrochemical permeation technique using the Devanathan–Stachurski permeation setup and the novel techniques are compared. The EPT technique is found to be more appropriate for laboratory assessment of hydrogen permeability due to generally better control over the experiment and data evaluation. The novel setups can be a good choice for comparative hydrogen measurements in real environments, including atmospheric ones, because of simpler sample preparation and small size of hydrogen probes.