Pure Hydrogen Research Articles

MoCx/CoP Janus Structure Embedded Carbon Frame for Boosting Hydrazine Oxidation and Hydrogen Evolution Reactions.

The integration of hydrazine electrooxidation (HzOR) and hydrogen evolution reaction (HER) presents an efficient pathway for high-purity hydrogen production. However, developing bifunctional catalysts remains challenging for the demands of multiple active-centers and tailored electronic properties. Here, a unique Janus nano-catalysts of MoCx/CoP embedded on carbon frameworks (MoCx/CoP@C) is introduced, featuring dual electronic states (depletion and accumulation)driven by charge redistribution within MoCx/CoP, acting as dual active-sites (DAS) for both HER and HzOR. Theoretical analysis reveals these independent DAS in MoCx/CoP significantly enhance catalytic activity for both HER and HzOR. Specifically, accumulated electrons at MoCx/CoP interfaces weaken the bonding strength of N-H in N2H4, thereby decreasing dehydrogenation energy barrier while electronic-deficient Mo sites within MoCx accelerate H* desorption, thus promoting HER kinetics. This catalyst exhibits ultra-low potential of -73mV at 10mA cm-2 for anodic HzOR, comparable to noble catalysts and low overpotential of 95mV at 10mA cm-2 for cathodic HER. When employed in an overall hydrazine splitting (OHzS) system, MoCx/CoP@C shows promising commercial potential, with low energy consumption (0.16V), high Faradaic efficiency (95.4%) and long-term stability. This study underscores the feasibility of designing independent DAS catalysts and elucidates the mechanistic origins of bifunctional activities.

Assessing the potential of low-temperature ironmaking using pure hydrogen in shaft reactors

Assessing the potential of low-temperature ironmaking using pure hydrogen in shaft reactors

Modelling hydrogen deblending from natural gas using Pd-based dense metallic membranes with an empirical polarization model

Low carbon hydrogen can be produced using excess of electric power and further stored into the existing natural gas grid. Deblending processes are required at the end-users side. However, conventional technologies such as adsorption methods can be complex, especially at the small scales, making the investment not convenient. Membrane technology is gaining interest. In scientific literature, Pd-based dense metallic membranes were already identified as a potential solution to separate high purity hydrogen. They can also be coupled with electrochemical hydrogen pump and TSA. However, Pd-based membrane potentiality had not yet been deeply investigated. In this article, a new empirical correlation for concentration polarization losses is found. Thanks to its simplicity and flexibility, it is used to show how an appropriate design of the separation modules can lead to outperform benchmark performance. Different scenarios, with blending at 5%, 10% and 20% and at low (8 bar), mid (40 bar) and high (66 bar) grid pressure are studied to separate 25 kg/day of pure hydrogen. Separation costs obtained with 10% hydrogen blending are below 4.44 €/kg even at low pressure, outperforming benchmark estimations using PSA, that resulted 7.64 €/kg. Polarization correlation is recommended to further improve module design in H2 deblending.

Poisoning effect of chlorine anions in the catalytic activity of CuO/CeO2/UiO-66 for CO-PROX reaction and strategy for catalyst activation.

UiO-66 was synthesized using ZrOCl2·8H2O as metal precursor, and CuO/CeO2/UiO-66 catalysts were prepared and tested for preferential CO oxidation in H2-rich streams (CO-PROX reaction), a reaction of practical significance in hydrogen purification for fuel cells. The study highlights the detrimental effect of residual chlorine anions from UiO-66 synthesis and DMF washing on the catalytic performance of CuO/CeO2/UiO-66. An activation strategy involving rigorous water washing and thermal treatment at 160 ºC under CO-PROX conditions was developed. Both steps were deemed necessary, as employing only one proved insufficient to reduce chlorine levels to non-poisoning thresholds. This activation procedure does compromise UiO-66 crystallinity and porosity, but it is justified by achieving a fully functional catalyst. TEM images confirm the uniform dispersion of the CuO/CeO2 active phase on the UiO-66 matrix post-activation and after catalytic testing. A 16-hour CO-PROX test at 160 ºC with the CuO/CeO2/UiO-66 catalyst, once activated, demonstrated stable performance throughout the extended long-term experiment. This research provides valuable insights into optimizing CuO/CeO2/UiO-66 catalysts for CO-PROX application.

Hydrogen generation through metal waste corrosion: a systematic investigation on old/post-consumer scrap Al6063-series alloy

In this study, aluminum-based wastes are used as energy carriers for on-demand hydrogen production through sustainable, eco-friendly, and cost-effective controlled electrochemical corrosion in aqueous solution. The electrochemical process is very effective because it (i) uses waste metals to produce hydrogen, (ii) corroborates to circular economy, (iii) produces high purity hydrogen, (iv) is based on simple hydrolysis reaction of metals in relevant solutions, (v) electricity is not required and (iv) recovers part of the chemical Gibbs energy of the electrochemical corrosion usually entirely lost in the environment. We systematically studied the generation of hydrogen from industrial waste Dust Scrap Aluminum Alloy (DSAA) belonging to Al 6063 series for the first time. The process is investigated in a novel hand-made batch reactor with a low-cost commercial body suitable to an easy scale-up. Kinetics of DSAA hydrolysis reaction was explored by measuring the variation of aluminium ion concentration at different immersion times through Inductively Coupled Plasma (ICP) and weight loss measurements at different temperatures and NaOH catalyst concentrations. The effect of hydrolysis reaction on the composition and morphology of the metal surfaces in terms of formed oxide layers was studied in detail using Optical Polarizing Microscopy (OPM), Energy dispersive X-ray (EDX) and Scanning Electron Microscopy (SEM) techniques. The criteria used to evaluate the hydrogen reactor performance were hydrogen (i) yield and (ii) production rate. The experimental results showed that a strong increase in NaOH concentration (from 0.75 to 5 M) corresponding to a slow increase in hydrolysis reaction temperature (from 38.8 to 49.9 °C) lead to an improvement in hydrogen generation rate of one order of magnitude, i.e. from 35.71 to 421.41 ml/(g∙min). Low but constant rate of hydrogen can be generated for longer times at low NaOH concentrations (0.75 M), while fast and variable hydrogen generation rate occurs at higher concentrations (5 M) in short times. In the case study of Al 6063 series waste scrap, the hydrolysis reactor parameters can be regulated to deliver hydrogen generation rates from 35.71 to 421.41 ml/(g min) according to requirements. We expect that the results presented in this work will encourage researchers to study the possible use of other metal-based and multi-material plastic/metal wastes thermodynamically prone to electrochemical corrosion process as possible source of hydrogen.Graphical

The 100 pc White Dwarf Sample in the SDSS Footprint. II. A New Look at the Spectral Evolution of White Dwarfs

Abstract We increase the spectroscopic completeness of the 100 pc white dwarf sample in the Sloan Digital Sky Survey footprint with 840 additional spectra. Our spectroscopy is 86% complete for white dwarfs hotter than T eff = 5000 K, where Hα remains visible and provides reliable constraints on the atmospheric composition. We identify 2108 DA white dwarfs with pure hydrogen atmospheres, and show that ultramassive DA white dwarfs with M ≥ 1.1 M ⊙ are an order of magnitude less common below 10,000 K. This is consistent with a fraction of them getting stuck on the crystallization sequence due to 22Ne distillation. In addition, there are no ultramassive DA white dwarfs with M ≥ 1.1M ⊙ and T eff ≤ 6000 K in our sample, likely because Debye cooling makes them rapidly fade away. We detect a significant trend in the fraction of He atmosphere white dwarfs as a function of temperature; the fraction increases from 9% at 20,000 K to 32% at 6000 K. This provides direct evidence of convective mixing in cool DA white dwarfs. Finally, we detect a relatively tight sequence of low-mass DQ white dwarfs in color–magnitude diagrams for the first time. We discuss the implications of this tight DQ sequence, and conclude with a discussion of the future prospects from the upcoming Ultraviolet Transient Astronomy Satellite mission and the large-scale multi-fiber spectroscopic surveys.

Polycalmagite Coating Enables Long-Term Alkaline Seawater Oxidation Over NiFe Layered Double Hydroxide.

Renewable energy-powered seawater electrolysis is a green and attractive technique for producing high-purity hydrogen. However, severe chlorideions (Cl-) and their derivatives tend to corrode anodic catalysts at ampere-level current densities and hinder the application of seawater-to-H2 systems. Herein, a polycalmagite (PCM)-coated NiFe layered double hydroxide is presented on Ni foam (NiFe LDH@PCM/NF) that exhibits exceptional stability in alkaline seawater. PCM not only acts as a conductive layer to reduce charge transfer resistance of the anodes but also as a polymer-based protective layer to inhibit Cl- adsorption and stabilize metal ions oxidation due to its own anions and strong adhesion, thereby increasing activity and stability during alkaline seawater. Thus, NiFe LDH@PCM/NF only needs a low overpotential of 364 mV to reach up to 1000 mA cm-2 and maintains operation for 500 h without activity degradation. Moreover, a minimal amount of hypochlorite can be detected in electrolyte after a 500-h stability test. This development affords a significant exploration in creating durable and efficient anodes, highlighting the importance of polymer coating toward anti-corrosion in alkaline seawater oxidation.

In‐Situ Formation of Three‐Dimensional Network Intrinsic Microporous Ladder Polymer Membranes with Ultra‐High Gas Separation Performance and Anti‐Trade‐Off Effect

AbstractThe global quest for clean energy and sustainable processes makes advanced membrane extremely attractive for energy‐intensive industrial gas separations. Here, we disclose a series of ultra‐high‐performance gas separation membranes (PIM‐3D‐TB) from novel network polymers of intrinsic microporosity (PIM) that combine the advantages of solution processible PIM and small pore size distribution (PSD) of porous organic polymers (POP), which was synthesized by in situ copolymerization of triptycene‐2,6‐diamine as linear part and triptycene‐2,6,13(14)‐triamine (TTA) as crosslinker. The resulting PIM‐3D‐TB membranes demonstrated outstanding separation properties that outperformed the latest trade‐off lines for H2/CH4 and O2/N2. They also showed an anti‐trade‐off effect by simultaneously enhancing gas permeability and gas‐pair selectivity with increasing TTA content. The TTA crosslinking node increased the microporosity, and, shifted the PSD from the ultramicropore (<7 Å) toward the more size sieving submicropore (<4 Å) region. The post‐treated TTA‐75 displayed an exceptional H2 permeability of 8000 Barrer and H2/CH4 selectivity of 208. These PIM‐3D‐TB membranes and their design protocol have unparalleled potential in the next generation of membranes for hydrogen purification and air separations.

In-Situ Formation of Three-Dimensional Network Intrinsic Microporous Ladder Polymer Membranes with Ultra-High Gas Separation Performance and Anti-Trade-Off Effect.

The global quest for clean energy and sustainable processes makes advanced membrane extremely attractive for energy-intensive industrial gas separations. Here, we disclosed a series of ultra-high-performance gas separation membranes (PIM-3D-TB) from novel network polymers of intrinsic microporosity (PIM) that combine the advantages of solution processible PIM and small pore size distribution (PSD) of porous organic polymers (POP), which was synthesized by in situ copolymerization of triptycene-2,6-diamine as linear part and triptycene-2,6,13(14)-triamine (TTA) as crosslinker. The resulting PIM-3D-TB membranes demonstrated outstanding separation properties that outperformed the latest trade-off lines for H2/CH4 and O2/N2. They also showed an anti-trade-off effect by simultaneously enhancing gas permeability and gas-pair selectivity with increasing TTA content. The TTA crosslinking node increased the microporosity, and, shifted the PSD from the ultramicropore (<7 Å) toward the more size sieving submicropore (<4 Å) region. The post-treated TTA-75 displayed an exceptional H2 permeability of 8000 Barrer and H2/CH4 selectivity of 208. These PIM-3D-TB membranes and their design protocol have unparalleled potential in the next generation of membranes for hydrogen purification and air separations.

On the Effectiveness of Aerosol Extinguishing Agents for Battery Vent Gases and Hydrogen

Abstract It is well known that Lithium-ion batteries in thermal runaway can emit gases with high hydrogen concentrations which, in case of delayed ignition, can cause a gas explosion. Aerosol suppression agents are sometimes used to suppress fires and/or prevent ignition of released gases in such situations. The agent has been studied for suppression of fires (diffusion flames), but less is known about the ability of such aerosols to inert highly reactive gas mixtures. In this paper, a commercially available aerosol suppression agent is mixed with a highly reactive gas mixture representing the gas composition from an NCA battery in thermal runaway as well as with pure hydrogen, and the effect on burning velocity is assessed based on OH-PLIF measurements on a Bunsen-burner type setup. The experiments were complemented by 1D flame simulations using a detailed chemical kinetics scheme including relevant combustible gases and the suppression agent. The results show that, although the agent is highly effective in gaseous form, evaporation of aerosols in the pre-flame-zone is prevented by the lower radiative fraction and results in higher burning velocity of hydrogen-rich mixtures. The local cooling induced by the evaporation of the aerosol in the flame leads to an increased flame area and thereby total burning velocity. This effect is further exaggerated by the preferential diffusion of hydrogen. Therefore, modification of the system is needed before applying for this purpose.

Evaluation of the Catalytic Effect of Metal Additives on the Performance of a Combined Battery and Electrolyzer System.

A low-cost method of green hydrogen production via the modification of a lead acid battery has been achieved, resulting in a hydrogen flow rate of 5.3 L min-1 from a 20-cell string. The electrochemical behavior and catalytic effect of various metal additives on the hydrogen evolution reaction (HER) was evaluated using cyclic voltammetry. Nickel, cobalt, antimony, manganese, and iron were investigated, with 66 ppm nickel achieving a 75% increase in hydrogen produced from a modified lead acid battery. Design of Experiments (DOE) employing a simple centroid design model to analyze the combined additive effects of nickel, cobalt, and antimony was performed to evaluate the effect on the HER. A combination of Ni:Co:Sb in the ratio 66:17:17 ppm achieved the greatest end voltage shift of the HER from -1.65 to -1.50 V; however, no increase in hydrogen yield was observed in comparison to 66 ppm of nickel when added to a full-scale cell. Gas chromatography using a thermal conductive detector and a sulfur chemiluminescence detector were used to measure the purity of hydrogen obtained from a string of 20 battery electrolyzer cells connected in series. 99% purity hydrogen gas was obtained from the battery electrolyzer cells, with H2S impurities below the limit of detection (0.221 ppm).

Enhancing Carbon Monoxide Tolerance in Low-Temperature PEM Fuel Cells through Carbon Nitride Surface Modification.

Low-temperature proton exchange membrane fuel cells (PEMFCs) reuqire highly pure hydrogen gas due to their extreme sensitivity to carbon monoxide (CO) contamination, which poses a challenge for using cost-effective reformed hydrogen sources. To address this issue, we have developed a surface modification strategy by applying a 0.5-0.91 nm amorphous carbon nitride layer onto PtRu/C substrates. The electrochemical measurements indicate that the modification selectively facilitates hydrogen gas transport to a surface while inhibiting carbon monoxide diffusion. The kinetic studies of CO adsorption reveal that the surface modification significantly reduces CO adsorption, effectively halving the rate compared to conventional catalysts. Additionally, rotating disk electrode experiments show that the catalyst modified with amorphous carbon nitride layer maintains stable operation for over 20 h with 1000 ppm of CO/H2. Furthermore, it supports stable discharge at 1 A cm-2 in PEMFCs with up to 10 ppm of CO, a concentration far exceeding the widely accepted standard of 0.2 ppm.

One-dimensional gold-doped monoclinic iridium oxide nanoribbons for high-efficiency acidic oxygen evolution reaction

Proton exchange membrane water electrolysis (PEMWE) stands as the predominant technique for the production of high-purity hydrogen. However, it is confronted with a significant impediment due to the sluggish kinetics...

In-situ immobilization of a novel fixed Z-scheme Ag|Ag2S/Ag/SnO2 photocatalytic system for pure hydrogen production and synchronous tartrazine degradation: Efficiency and mechanism insight

In-situ immobilization of a novel fixed Z-scheme Ag|Ag2S/Ag/SnO2 photocatalytic system for pure hydrogen production and synchronous tartrazine degradation: Efficiency and mechanism insight

Roll-to-Roll Flash Joule Heating to Stabilize Electrocatalysts onto Meter-Scale Ni Foam for Advanced Water Splitting.

The seamless integration of electrocatalysts onto the electrode is crucial for enhancing water electrolyzers, yet it is especially challenging when scaled up to large manufacturing. Despite thorough investigation, there are few reports that tackle this integration through roll-to-roll (R2R) methodology, a technique crucial for fulfilling industrial-scale demands. Here, we develop an R2R flash Joule heating (R2R-FJH) system to process catalytic electrodes with superior performance. The electrodes exhibited improved stability and activity, showcasing an exceptional performance within an alkaline water electrolysis (AWE) system. They achieved a low operation potential of 1.66 V at 0.5 A cm-2, coupled with outstanding durability over the operation of 800 h. We further demonstrated a prototype of a rolled-up water splitting apparatus, illustrating the efficiency of R2R-FJH electrodes in producing high-purity hydrogen through advanced water oxidation. Our study emphasized the practicality and scalability of the R2R-FJH strategy in the industrial manufacturing of high-performance electrodes for water electrolysis.

Study of metrological characteristics of household gas meters when measuring the volume flow rate of gas-hydrogen mixtures

The paper presents the results of studies of the influence of pure gaseous hydrogen and gas-hydrogen mixtures and the performance and metrological characteristics of membrane-type gas meters used in the household sector. For the study, membrane-type meters of leading domestic and European manufacturers were pre-selected. A series of static and dynamic tests were conducted for the meters. The static tests involved checking the air-tightness of the meters under the influence of gaseous mixtures. The dynamic tests involved measurements on a simulated test site with a work medium of pure hydrogen as well as hydrogen-methane mixtures. The proportions of the mixtures used were: 80% of methane and 20% of hydrogen, and 90% of methane and 10% of hydrogen respectively. A structural diagram of the measuring system was developed. The measurements were performed by comparing the volume of the gas that passed through the experimental meter with the volume measured by the reference meter. The measuring system was equipped with a means for measuring the pressure and temperature of the measuring medium to bring the results of the experiments to standard conditions. As a reference means in the assembled measuring system, a drum-type gas meter with a calibration characteristic pre-determined under laboratory conditions with a work air medium was used. After the experimental studies with the work hydrogen medium and hydrogen gas mixtures under the conditions of the test site, the metrological characteristics were re-determined under laboratory conditions for the reference meter. To conduct the experiments with the maximum possible accuracy and to exclude the influence of additional errors on the measurement result, a specialized software was developed to automate the measurements of the volume of the gas passing through the reference meter, measuring the pressure and temperature of the work medium and fixing the required value of the gas volume flow rate. The results of the experiments for several meters are presented in the form of tabular values and graphs. General conclusions were made regarding the influence of hydrogen and gas-hydrogen mixtures on the change in metrological characteristics of household gas meters.

A Novel Optimization Method Using the Box–Behnken Design Integrated with a Back Propagation Neural Network–Genetic Algorithm for Hydrogen Purification

Pressure swing adsorption (PSA) technology is among the most efficient techniques for purifying and separating hydrogen. A layered adsorption bed composed of activated carbon and zeolite 5A for a gas mixture (H2: 56.4 mol%, CH4: 26.6 mol%, CO: 8.4 mol%, N2: 5.5 mol%, CO2: 3.1 mol%) PSA model was built. The simulation model was validated using breakthrough curves. Then, a six-step PSA cycle model was built, and the purification performance was studied. The Box–Behnken design (BBD) method was utilized in Design Expert software (version 10) to optimize the PSA purification performance. The independent optimization parameters included the adsorption time, the pressure equalization time, and the feed flow rate. Quadratic regression models can be derived to represent the responses of purity and productivity. To explore a better optimization solution, a novel optimization method using machine learning with a back propagation neural network (BPNN) was then proposed, and a kind of heuristic algorithm–genetic algorithm (GA) was introduced to enhance the architecture of the BPNN. The predicted outputs of hydrogen production using two kinds of models based on the BPNN–GA and the BBD method integrated with the BPNN–GA (BBD–BPNN–GA). The findings revealed that the BBD–BPNN–GA model exhibited a mean square error (MSE) of 0.0005, with its R–value correlation coefficient being much closer to 1, while the BPNN–GA model exhibited an MSE of 0.0035. This suggests that the BBD–BPNN–GA model has a better performance, as evidenced by the lower MSE and higher correlation coefficient compared to the BPNN–GA model.

Comparison of composite metal oxides as oxygen carrier for methane chemical looping reforming

Abstract The amount of greenhouse gases has increased considerably in recent years. Additionally, the energy required by humanity for daily activities is also on the rise. The planet is facing one of its worst crises, characterized by the overexploitation of fossil fuels due to population growth. It is estimated that by 2050, the global population will exceed 9 billion inhabitants. Chemical looping combustion (CLC), offers a potential solution. This process involves usually two interconnected reactors, usually with a fluidized bed, where combustion takes place in an alternate way. In this process, the oxygen required for combustion is provided by a solid oxygen carrier, the capacity of this depends on the nature of the material and is crucial to define the most effective one by a comparative study. Moreover, methane emissions are a significant concern, as methane is a potent greenhouse gas with a 25 times greater impact on the atmosphere compared to carbon dioxide as greenhouse gases. To address this, methane reforming in chemical cycles, such as Steam Reforming Chemical Looping Combustion (SR-CLC) or chemical looping reforming (CLR), is proposed. Using a Gibbs reactor and oxygen carrier data reported in the literature, the analysis of NiWO4, FeMoO4, Fe2MnO4 and FeZnO4, their operation, energy yield when exposed to a methane stream and the comparison between different forms of reforming schemes, as well as the estimation of the carrier needed for the process, are presented. Results indicate that after calculations, the g-carrier/g-fuel ratio for NiWO4 is almost 100 % higher than the other carriers studied in this work. Water vapor reforming generates 30.0930 kW and a stream of pure hydrogen that can be separated while carbon dioxide reforming is a general endothermic process that requires 12.22 kW of energy for this process scheme. Once the ideal carrier has been analyzed, the proposed future work should focus on the optimal design of a reaction system that will allow it to operate efficiently under the conditions encountered. In addition, it will be necessary to find the replacement rate for the carrier that will allow us to operate our system continuously.

The Use of Microwave Treatment as a Sustainable Technology for the Drying of Metallurgical Sludge.

The modern metallurgical industry produces approximately 90% of the volume of all produced steel; for this, integrated technology based on fossil materials such as coal, fluxes, and especially iron ore is used. This industry generates large amounts of waste and by-products at almost all stages of production. Alternative iron and steel production technologies based on iron ore, methane, or pure hydrogen are also not waste-free. To ensure sustainable waste management, efforts are made to seal processes as well as capture and recycle dusty waste. This work presents the results of research on the processing of sludge resulting from the dedusting of the basic oxygen furnace (BOF) process and landfilling in a lagoon. The work discusses the treatment of fine dusty sludge hydrated to 26-60% H2O, to which various amounts of caking agents were added; also discussed are the rheological characteristics of the tested suspension systems, the possibility of forming these systems into larger fractions, and rapid drying using 100-600 W microwaves with a drying time of 1-9 min. The aim was to identify, describe, and characterize the parameters of the agglomeration process and obtain a product that was durable enough to transport and dose into slag baths in order to reduce iron oxides in liquid phases. During the research, completely dried briquettes with an appropriate strength were obtained. The study demonstrates that microwave drying at 300 W for 6 min achieved complete drying with a weight loss of 35%, whereas a higher-power treatment at 750 W for 2 min enhanced compressive strength by up to 95% and reached 15 N/psc, which was comparable with green iron ore pellets. This approach offers a sustainable alternative to traditional methods, but with a reduced drying time.

Faint White Dwarf Flux Standards: Data and Models

Abstract Fainter standard stars are essential for the calibration of larger telescopes. This work adds to the calibration spectra (CALSPEC) database of 19 faint white dwarfs (WDs) with all-sky coverage and V magnitudes between 16.5 and 18.7. Included for these stars is a new ultraviolet (UV) Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph between 1150 and 3000 Å with a resolution of ∼500. Pure hydrogen WD models are fit to these UV spectra and to six-band HST/Wide Field Camera 3 photometry at 0.28–1.6 μm to construct predicted model spectral energy distributions covering wavelengths from 900 Å to the James Webb Space Telescope limit of 30 μm using well-established CALSPEC procedures for producing flux standards with the goal of 1% accuracy.