High Hydrogen Research Articles

Electric field-driven assembly of (110) oriented metal–organic framework ZIF-8 monolayer with high hydrogen selectivity

Metal-organic framework (MOF) membranes have showed great potential in gas separation. To date, it is still a great challenge to precisely control the optimal orientation of MOF membranes with an enhanced gas separation performance. Herein, we prepared a compact and (110) oriented ZIF-8 membrane with a thickness of about 265 nm on graphite substrate within 1 h at room temperature via electric-field-driven strategy. Since the membrane is an intergrown one-crystal layer, grain boundary retardation of the flux is eliminated. Furthermore, due to the reduction of the transport pathways through the oriented structure, the (110) oriented ZIF-8 membrane exhibits a high gas separation performance. At 100 °C and 1 bar for the separation of equimolar binary gas mixtures H2/CO2, H2/CH4 and H2/C3H8, separation factors of 49.5, 90.9 and 121.8 can be obtained, with H2 permeance of about 1.7 × 10-7 mol·m−2·s−1·Pa−1. The developed strategy exhibits excellent reproducibility and scalability, and a large area ZIF-8 membrane can be consistently prepared on the graphite substrate, thus facilitating the preparation and application of the ZIF-8 membrane on a large scale. Further, the electric-field-driven strategy is also helpful for the preparation oriented ZIF-67 and ZIF-L membranes, confirming its versatility for the preparation of oriented MOF membranes.

Polymer-Supported Pd Nanoparticles for Solvent-Free Hydrogenation.

Breaking the trade-off between activity and stability of supported metal catalysts has been a long-standing challenge in catalysis, especially for metal nanoparticles (NPs) with high hydrogenation activity but poor stability. Herein, we report a porous poly(divinylbenzene) polymer-supported Pd NP catalyst (Pd/PDVB) with both high activity and excellent stability for the solvent-free hydrogenation of nitrobenzene, even at ambient temperature (25 °C) and H2 pressure (0.1 MPa). Pd/PDVB gave a turnover frequency as high as 22,632 h-1 at 70 °C and 0.4 MPa, exceeding 5556 h-1 of the classical Pd/C catalyst under equivalent conditions. Mechanistic studies reveal that the polymer support benefits the desorption of the aniline product from the Pd surface, which is crucial for rapid hydrogenation under solvent-free conditions. In addition, the polymer support in Pd/PDVB efficiently hindered Pd leaching, resulting in good stability.

One-step fabrication of AlPO4 nanosheet reinforced ceramic coatings with improved fracture toughness and hydrogen resistance

Ceramic coatings have great potential in protecting vital metal structural components in hydrogen energy and nuclear fusion reactors. Fracture toughness and hydrogen permeation resistance are two key characteristics that determine life span and performance of these coatings. However, there is still no strategy to simultaneously enhance both of these two characteristics. Herein, we developed a one-step approach to fabricate AlPO4 nanosheet reinforced α-Al2O3 ceramic coating with simultaneously enhanced fracture toughness and hydrogen permeation resistance. Different from the external nanosheet addition method of the conventional techniques for fabricating nanosheet reinforced coatings, AlPO4 nanosheets were in-situ formed within α-Al2O3 ceramic coating though a one-step heat treatment process. Owing to the positive reinforcing effect of AlPO4 nanosheets, the fracture toughness of the coating increases by 3 times, achieving an ultrahigh KIC value of 7.1 MPa/m2. Meanwhile, the hydrogen permeation resistance of the coating increases by 78 %, reaching as high as 3440 times that of the steel substrate. Additionally, the Cr–P bonds formed between the coating and substrate ensure their good bonding, with their bonding strength increasing up to 36 MPa. The combination of high hydrogen permeation resistance, high fracture toughness, and high bonding strength makes the AlPO4 nanosheet reinforced ceramic coating a promising alternative for reducing hydrogen permeation in various hydrogen-related fields. This study also provides critical insights and practical guidelines for constructing high-performance functional coatings via nanosheet reinforcement.

Enhanced stability in Co0.8Ni0.2/NDMCS catalysts: Carbon nitride encapsulation for robust hydrogen generation

Catalytic hydrolysis of NaBH4 is a promising method for "on-demand" hydrogen generation, with cobalt catalysts playing a key role due to their high hydrogen generation rates. However, rapid cobalt dissolution and poor recycling hinder stable hydrogen production. This study presents a dual-mode stabilization technique using carbon nitride encapsulation to address these challenges. Co0.8Ni0.2 alloy nanoparticles (NPs) are confined within N-doped mesoporous carbon spheres (NDMCS) and encapsulated with a carbon nitride shell (∼ 5 nm thick). XPS results reveal strong non-classical metal-support interaction, increasing activation energy from 38.82 to 44.6 kJ mol−1, which controls cobalt's reactivity, leading to excellent recycling efficiency (90 % retention of initial rate, no change in particle size) in high-concentration reactants (2 %NaBH4 + 2 %NaOH). The retention rate drops to 26.8 % without this stabilization due to rapid metal dissolution. This stability of Co0.8Ni0.2 alloy in alkaline conditions has significant practical implications for hydrogen generation and other electrochemical applications.

The Determination of Woody Biomass Resources and Their Energy Potential from Hazelnut Tree Cultivation

The aim of this study was to estimate the shoot weight of four selected hazelnut cultivars and to see if the morphological characteristics of the cultivar and the age of the shoots affect their quality when used as fuel. This study shows that the cultivar ‘Olga’ generated the highest amounts of woody biomass (6507 t·ha−1), while ‘Olbrzymi z Halle’ generated the lowest (3843 t·ha−1). ‘Olbrzymi z Halle’ had the highest calorific values (HHVs) (18.08 MJ·t·ha−1 for annual shoots and 18.03 MJ·kg−1 for perennial shoots) and ‘Olga’ had the lowest calorific values (16.64 MJ·kg−1 for annual shoots and 16.39 MJ·kg−1 for perennial shoots). The age of the shoots had a minimal effect on the chemical and energy parameters. Emissions were the highest for ‘Olbrzymi z Halle’ (CO: 57.74 MJ·kg−1 for perennial shoots, CO2: 1414.05 MJ·kg−1) and lowest for ‘Olga’ (CO: 50.57 MJ·kg−1, CO2: 1238.46 MJ·kg−1). The cultivar ‘Olbrzymi z Halle’, which generated the least amount of biomass compared to the other cultivars, stands out for its high energy value due to its low moisture and ash contents and its high carbon and hydrogen contents, making it attractive for the purposes of biofuel production and supporting sustainable agriculture. The practical implications of the research findings include the selection of suitable varieties for biofuel production, the management of biomass moisture content, and the optimisation of combustion techniques to reduce emissions. The potential for using hazelnut shoots as a biofuel highlights the importance of sustainable agriculture and renewable energy production. The results provide valuable information that can support decisions regarding the cultivation and use of hazelnut shoots for biofuel production while minimising negative environmental impacts.

Atomic effect and mechanism of different hydrogen content on superlubricity properties of H-DLC films

Hydrogen atoms play a pivotal role in achieving superlubricity in DLC films. Nevertheless, the inherent limitations in analytical testing techniques obscure the mechanisms by which hydrogen atoms achieve superlubricity in DLC films. Furthermore, direct evidence supporting the widely accepted mechanism of hydrogen passivation remains elusive. Therefore, we used ReaxFF MD simulations to investigate the effects of different hydrogen content on the tribological and wear properties of hydrogen-doped H-DLC films. Hydrogen atoms diffuse from the DLC films and gradually accumulate on the friction surface during the sliding, effectively passivating and inhibiting the C–C bonds at the interface. This reduces cross-linking between H-DLC films, consequently loweringfrictiontemperature significantly during the sliding. A significant release of hydrogen atoms during the friction process weakens the strength of machinery of H-DLC films, potentially causing structural failures under hydrogen-rich conditions, with the released hydrogen atoms subsequently occupying structural voids within films. At the microscopic scale, the friction of H-DLC film decreases with the increase of hydrogen content, but when the hydrogen content reaches 40 % or above, the local collapse of the system will be caused, resulting in the failure of superlubricity. Finally, the friction and wear of H-DLC film under high hydrogen conditions will rebound.

Chemical-guided screening of top-performing metal–organic frameworks for hydrogen storage: An explainable deep attention convolutional model

Metal-organic framework (MOF)-based adsorptive hydrogen storage holds promise for enhancing the sustainable design of hydrogen storages by enhancing the usable volumetric (UV) and gravimetric (UG) capacities. However, the extensive number of MOFs poses a challenge in the search for optimal materials owing to the lack of an efficient and interpretable high-throughput screening method. This study introduces an explainable artificial intelligence (XAI) framework to expedite the discovery of high-capacity hydrogen adsorbents by predicting the UV and UG capacities using an attention densely connected convolutional (ADCC) network. A new hybrid dataset with various operating conditions and comprising 24 physical–chemical descriptors, such as void fraction (VF) and metal percentage (MP), was utilized to develop the ADCC model. The explainable ADCC model demonstrated superior predictive performance for the UV and UG capacities, with R2 values of 0.9886 and 0.9982, respectively. The inclusion of the chemical descriptors MOFs enhanced the prediction accuracy of the ADCC model. The XAI analysis showed that VF and MP dominated physical and chemical descriptors, respectively, for UV and UG. Consequently, the ADCC model identified EFAYIU—a real MOF—as a promising hydrogen storage material with UV and UG capacities of 51.55 g H2/L and 11.37 wt%, respectively, surpassing the current materials for hydrogen storage. Additionally, the identified EFAYIU was validated based on molecular simulations, confirming the high hydrogen adsorptive capacities obtained by the ADCC model. Thus, the proposed AI-based high-throughput screening method enables the rapid discovery of high-performance MOFs for sustainable hydrogen storage.

First principles investigation for the hydrogen storage properties of novel lithium-based XLiH3 (X=K, Rb) perovskite-type hydrides for advance hydrogen storage system

In this work, the density functional theory is used to investigate the structural, mechanical, electronic, dynamic, thermodynamic, optical and hydrogen storage properties of XLiH3 (X = K, Rb) for the first time. Both KLiH3 and RbLiH3 materials exhibit dynamic, mechanical and thermodynamic stability. The lattice parameters of KLiH3 and RbLiH3 are 3.908 and 4.070 Å, respectively. The investigation of Cauchy pressure, Poisson's ratio and B/G ratio shows that KLiH3 and RbLiH3 are brittle materials. Moreover, the electronic properties of XLiH3 hydrides demonstrate that KLiH3 and RbLiH3 show metallic nature. Optical properties of these compounds are studied and reveal that they have very high refractive indexes and dielectric functions. The thermodynamic properties, including heat capacity, entropy, enthalpy, and free energy of XLiH3, are investigated as well. The hydrogen storage capacities of KLiH3 and RbLiH3 are 5.805 and 3.071 wt%, respectively, confirming that KLiH3 has a high hydrogen storage capacity and is more suitable as a hydrogen storage material. Our study opens up a new-pathway for designing novel hydrogen storage materials.

Investigating the Fatigue Response of Cathodically Charged Cold-Finished Mild Steel to Varied Hydrogen Concentrations

This study investigates the fatigue behavior of cold-finished mild steel subjected to electrochemical hydrogen charging under controlled conditions. Samples were subjected to hydrogen charging at constant time in a fixed electrolyte pH, after which the samples underwent fatigue testing under constant loading condition with fixed frequency. The primary objective was to assess the impact of varying hydrogen permeation levels on the number of cycles to failure. The experimental results revealed a complex relationship between hydrogen concentration and fatigue life. Initially, as hydrogen permeation increased, the number of cycles to failure substantially decreased, demonstrating the detrimental effect of diffused hydrogen on the fatigue resistance of samples. This decline in fatigue life was attributed to hydrogen embrittlement (HE) and hydrogen-enhanced decohesion (HEDE) phenomena, which collectively facilitate crack initiation and propagation. However, at high hydrogen concentrations, an unexpected increase in the number of cycles to failure was observed suggesting the existence of a threshold hydrogen concentration beyond which the fatigue mechanisms may be altered, potentially due to a saturation of hydrogen-related defects and mechanisms such as hydrogen-enhanced localized plasticity (HELP). The discovery from this research has significant implications for the material’s application in hydrogen-rich environments, such as those encountered in the energy and transportation industries.

Effect of heat input on the microstructure and hydrogen embrittlement susceptibility of the coarse-grain heat-affected zone of CrMo steels generated using a Gleeble 3500 welding simulator

The changes in microstructure and hydrogen embrittlement (HE) susceptibility of the simulated coarse-grain heat-affected zone (CGHAZ) of CrMo steels under three distinct heat input conditions were investigated. The cooling time from 800 °C to 500 °C, represented by t8/5, increased from 100 s to 200 and 400 s.. The sample with t8/5 = 100 s has a microstructure consisting of martensite and a small amount of lower bainite. When the t8/5 was increased to 200 s and 400 s, the HAZ consisted of 65.43 % martensite and 34.57 % lower bainite and 4.53 % martensite with 95.47 % bainite, respectively. The HE susceptibility was assessed by slow strain rate tensile (SSRT) testing of hydrogen-charged samples, and the HE susceptibility index (IHE) declined from 87.89 % to 61.37 % when t8/5 increased from 100 to 400 s. The high dislocation density and hydrogen concentration in the sample with t8/5 = 100 s led to intergranular fracture and incresaed HE susceptibility. The martensite lath and cementite/ferrite interface are the sites of crack initiation in the sample with t8/5 = 200 s. In the sample with a cooling time of 400 s, the martensite/ferrite interfaces are the main crack initiation sites under hydrogen charging.

Unlocking solar energy's potential: Dual photocatalytic activities of g-C3N4/Sb2S3 for hydrogen evolution and tetracycline degradation in sunlight

This study focuses on developing a g-C3N4/Sb2S3 heterojunction photocatalyst with different g-C3N4 to Sb2S3 weight ratios (1:1, 1:3, and 3:1) for degrading tetracycline (TC) pollutants. The 1:3 ratio (13 GS) exhibited optimal photocatalytic performance, achieving 99% TC degradation under sunlight within 120 min, compared to 78.4% under visible light and 38% under UV light. The 13 GS catalyst demonstrated strong reusability, maintaining 80% degradation efficiency after six cycles. Scavenger experiments identified hydroxyl radicals as crucial for TC degradation, with DMSO reducing activity by 30%. The photocatalyst also showed high hydrogen production with an apparent quantum efficiency (AQE) of 19.8% under standard conditions, and improved AQE in acidic (23%) and basic (22.7%) conditions, and with CH3OH (23.2%). This g-C3N4/Sb2S3 heterojunction offers a promising solution for degrading toxic contaminants and has the potential for solar-powered applications.

Microwave catalytic co-pyrolysis of microalgae and high density polyethylene over activated carbon supported bimetallic: Characteristics and bio-oil analysis

Three activated carbon (AC) supported bimetallic catalysts (Ce-Fe/AC, Ce-Ni/AC, Ce-Cu/AC) were prepared, and the catalysts' impacts on the microwave co-pyrolysis of Chlorella vulgaris (C. vulgaris) and high density polyethylene (HDPE) (mixing ratio of 1:1, C1HP1) were explored. The findings indicated that the catalysts promoted the co-pyrolysis of C1HP1 substantially at 40 % and 50 % additions. The minimum reaction time (2945 s) was observed at 40 % Ce–Fe/AC. Compared to the C1HP1 group, Ce-Fe/AC groups exhibited a pronounced promotional impact on bio-oil production, with the maximum bio-oil yield (25.8 %) catalyzed by 30 % Ce–Fe/AC. Furthermore, the catalyst's high hydrogenation activity and deoxygenation promoted the formation of H2O, NH3 and HCN, achieving over 40 % efficiencies in deoxygenation and denitrification for bio-oil. 40 % Ce–Cu/AC exhibited superior performance with the highest hydrocarbon (67.43 %) and aromatic hydrocarbon content (50.75 %), as well as leading deoxygenation (44.38 %) and nitrogen removal (58.63 %) efficiency among the AC supported bimetallic catalysts.

Quantifying concentration distributions in redox flow batteries with neutron radiography

The continued advancement of electrochemical technologies requires an increasingly detailed understanding of the microscopic processes that control their performance, inspiring the development of new multi-modal diagnostic techniques. Here, we introduce a neutron imaging approach to enable the quantification of spatial and temporal variations in species concentrations within an operating redox flow cell. Specifically, we leverage the high attenuation of redox-active organic materials (high hydrogen content) and supporting electrolytes (boron-containing) in solution and perform subtractive neutron imaging of active species and supporting electrolyte. To resolve the concentration profiles across the electrodes, we employ an in-plane imaging configuration and correlate the concentration profiles to cell performance with polarization experiments under different operating conditions. Finally, we use time-of-flight neutron imaging to deconvolute concentrations of active species and supporting electrolyte during operation. Using this approach, we evaluate the influence of cell polarity, voltage bias and flow rate on the concentration distribution within the flow cell and correlate these with the macroscopic performance, thus obtaining an unprecedented level of insight into reactive mass transport. Ultimately, this diagnostic technique can be applied to a range of (electro)chemical technologies and may accelerate the development of new materials and reactor designs.

Rapid hydrogen enclathration and unprecedented tuning phenomenon within superabsorbent polymers

Clathrate hydrate has emerged as a potentially viable storage medium for efficient hydrogen storage, owing to its eco-friendly characteristics and high hydrogen storage capacity. However, it is essential for its practical application to address the challenges posed by harsh thermodynamic formation conditions and slow formation kinetics for hydrogen hydrate. Here, we introduce the utilization of superabsorbent polymers (SAPs) as a dispersion matrix for tetrahydrofuran (THF) solutions to develop a method for rapid hydrogen enclathration. We investigated two distinct synthetic pathways, solution-borne and hydrate-borne routes. We also explored the relationship between hydrogen uptake/storage capacity, varying THF solution concentration within SAPs, and synthetic pathways for binary THF–hydrogen hydrates. The hydrogen storage capacity after 200 min enclathration reaction was relatively low for 1.0 mol% THF cases but significant for 5.56 mol% THF cases in hydrate-borne route (around 20 mmol H2/mol water), highlighting its potential for hydrogen storage material. The spectroscopic analysis revealed that the tuning phenomenon in THF 1.0 mol% hydrate was only observed in the solution-borne route, which facilitated hydrogen enclathration in partially vacant large cages of sII hydrates. It was striking that the tuning phenomenon was also observed in THF 5.56 mol% hydrate synthesized in both solution-borne and hydrate-borne pathways. Through phase equilibria measurements, we confirmed that less than 5.56 mol% of THF participated in forming binary hydrates. The different water and THF absorbability of SAPs resulted in a non-uniform distribution of THF solution within SAPs, causing the unprecedented tuning phenomenon. These findings provide valuable insights into the potential of SAPs for rapid hydrogen enclathration media, emphasizing the importance of understanding synthetic pathways and solution absorption properties for optimized hydrogen storage.

Magnetic Co2Si monolayer with high performance hydrogen evolution reaction: a first-principle prediction

Magnetic Co2Si monolayer with high performance hydrogen evolution reaction: a first-principle prediction

Design and multi-objective optimization of hybrid process of membrane separation and electrochemical hydrogen pump for hydrogen production from biogas

A new hybrid process for hydrogen (H2) production that including membrane separation, electrochemical hydrogen pump (EHP) and steam methane reforming (SMR) was proposed. Firstly, the combination of two different membranes (PEO-CA) is applied to upgrade the biogas and capture CO2. Secondly, to avoid the toxic effect of CO on the EHP catalyst and, more importantly, to improve the H2 purity, the reforming reaction module is supplemented with water gas shift after the SMR. Finally, EHP is used to achieve high purity hydrogen. Simultaneously, the heat and power integration are considered to improve system efficiency. Sensitivity analysis, maximal information coefficient method and response surface methodology are applied to establish the correlation between objectives and parameters. Then, the second generation multi-objective non-dominated genetic algorithm (NSGA-II) is utilized to achieve minimum levelized cost of hydrogen (LCoH) and carbon emission per unit of hydrogen (ECO2). The optimized LCoH is 2.72 $/kgH2, and the ECO2 is 3.24 kgCO2e. Multi-stage membrane carbon capture process enhances CH4 conversion in SMR. The application of EHP reduces energy consumption and enhances hydrogen yield compared to PSA. The innovative use of membrane is hybridized with EHP to achieve the system intensification. The new hybrid process has a significant advantage in terms of ECO2 (37.45% reduction), although the price is higher compared to conventional biogas-to-hydrogen processes. Thus the new process is a promising low-carbon hydrogen production process from biogas.

ASSESSMENT OF THE POSSIBILITY OF USING A CO₂-BASED BUFFER WHEN ORGANIZING UNDERGROUND GAS STORAGE FACILITIES

The burial of CO2 in geological structures is considered to be current direction for reducing the negative impact of anthropogenic load in the form of greenhouse gases. Underground storage is also evaluated as a potential way to balance hydrogen production and consumption. The planned production of hydrogen in Russia by 2030 is expected to reach several billion m3 per year. To ensure the production and transportation of such volumes of gas, a hydrogen storage system is needed. Above-ground complexes and storage facilities in salt caverns cannot provide the required storage volumes. Aquifers are promising objects for long-term storage of both CO2 and hydrogen, including as part of a hydrogen-methane mixture.The work considers a hydrogen-methane mixture with a hydrogen concentration of 10–30 %, which is an economically justified value in most cases when producing this mixture.When storing hydrogen long-term in underground gas storage facilities, an important task is to assess hydrogen losses during storage.The authors, using linear hydrodynamic models taking into account phase transformations and hydrochemical effects, assessed the effectiveness of simultaneous CO2 burial and underground hydrogen storage through the injection of a hydrogen-methane mixture with a CO2 buffer rim.The models under consideration take into account: changes in the ionic composition of formation water, dissolution and precipitation of minerals.Analysis of the results showed that CO2 is not an effective buffer for the hydrogen-methane mixture even under the simplified conditions of the linear model. In this model, the region with a high hydrogen content disintegrates. At the same time, linear models do not take into account a number of negative factors that arise during the creation and operation of a full-fledged underground gas storage facility.

Energy Hub Model for the Massive Adoption of Hydrogen in Power Systems

A promising energy carrier and storage solution for integrating renewable energies into the power grid currently being investigated is hydrogen produced via electrolysis. It already serves various purposes, but it might also enable the development of hydrogen-based electricity storage systems made up of electrolyzers, hydrogen storage systems, and generators (fuel cells or engines). The adoption of hydrogen-based technologies is strictly linked to the electrification of end uses and to multicarrier energy grids. This study introduces a generic method to integrate and optimize the sizing and operation phases of hydrogen-based power systems using an energy hub optimization model, which can manage and coordinate multiple energy carriers and equipment. Furthermore, the uncertainty related to renewables and final demands was carefully assessed. A case study on an urban microgrid with high hydrogen demand for mobility demonstrates the method’s applicability, showing how the multi-objective optimization of hydrogen-based power systems can reduce total costs, primary energy demand, and carbon equivalent emissions for both power grids and mobility down to −145%. Furthermore, the adoption of the uncertainty assessment can give additional benefits, allowing a downsizing of the equipment.

Identifying sulphurous water discharge from legacy oil and gas wells using spectral band analysis of aerial and satellite imagery

Legacy oil and gas wells are a significant source of hydrogen sulphide and methane gas release to the atmosphere. Unanticipated occurrences of gas release in urbanized areas can pose human health risks. Several high hydrogen sulphide-emitting wells have been identified in Norfolk County, Ontario, Canada, based on the remote detection of sulphurous water discharging to the surface along the wellbore. Although oil and gas well records report well status and location, community reports of noxious hydrogen sulphide odours suggest potentially compromised well seals and inaccuracies in their documented location. Given the broad-scale nature of this issue and limitations in site access, a remote-sensing based methodology utilizing satellite and high-resolution aerial photography could support identification of undocumented sulphurous water leaks associated with compromised oil and gas wells and subsequent characterization of hydrological and ecohydrological impacts over time. This study presents a multifaceted approach to identifying sulphurous leaking wells utilizing complimentary remote sensing imagery and image analysis tools within ArcGIS. Southwestern Ontario Orthophotography Project air photos and Sentinel-2 satellite imagery were determined to be the most applicable sources of imagery based on their respective advantages in resolution and revisit time. The application of a normalized difference vegetation index showed that major well leaks could exhibit signs of vegetative scarcity, while minor well leaks may have only a limited impact on vegetation. A band combination utilizing the green and near infrared bands was created to enhance the detection of sulphurous water leaks. Utilizing the identified band combination, a pair of potentially undiscovered leaks were located west of a fluvial river channel. Continued research should attempt to employ an automated approach for discerning additional sulphurous water leaks in the region or at different points in time. Possible techniques may involve the deep learning object and change detection models incorporated in ArcGIS.

Effect of Hydrogen Pressure on The Mass Transfer Characteristics of Hydrogen-Bromine Flow Battery Electrodes

The mass transfer characteristics of porous carbon electrodes in the liquid side of a hydrogen bromine redox flow battery (H2-Br2 RFB) were investigated under compressive deformation caused by operation at elevated hydrogen pressure. Here, flow cell measurements of permeability and micro-particle image velocimetry (μPIV), alongside electrochemical measurements of capacitance and battery discharge were used to characterize changes in the liquid side electrode compression, in-plane liquid flow, accessible surface area, polarization, and mass transfer scaling brought by hydrogen pressure. We studied two electrode types with different structures, carbon paper and carbon cloth, in untreated well as heat-treated forms in the pressure range 0–8 bar H2. It was found that pressure-induced compression of the liquid side electrode increases the accessible area of untreated electrodes, with little effect on heat-treated electrodes, but decreases the electrochemical performance of the battery in all cases by increasing the ohmic resistance of the cell and decreasing the mass transfer coefficient of the porous electrode. Overall, heat treatment is shown to affect the rigidity, saturation behavior, and generalized mass transfer of paper electrodes but not of cloth electrodes. Our findings will guide the selection of electrode materials and operation parameters for the H2-Br2 RFB.