High Hydrogen Research Articles

Boosting Hydrogen Production: Non-Noble Metal Catalysts Optimize Electrodes in Anion Exchange Membrane Water Electrolysis

As the world transitions to renewable energy sources, efficient energy storage is crucial for managing power fluctuations and decarbonize crucial high temperature processes. Achieving grid balance and optimizing renewable energy capacity requires innovative solutions. One promising option is the conversion of electrical energy into hydrogen through Anion Exchange Membrane Water Electrolysis (AEM-WE).AEM-WE combines high hydrogen production rates per electrode area and little production site footprint of Proton Exchange Membrane Water Electrolysis (PEM-WE) with cost-effectiveness of non-noble electrode materials utilized in Alkaline Water Electrolysis (A-WE). To further optimize AEM-WE, it is essential to improve hydrogen production while reducing material costs. This can be achieved through innovative approaches to electrocatalyst and electrode design. However, developing cost-effective catalysts that combine superior efficiency and robustness in aqueous environments, ideally in alkaline conditions, remains a big challenge. In this work, two electrode preparation approaches are investigated. For the anodic OER a corrosion synthesis is been developed to form highly active NiFe-layered double hydroxide (LDH) structures on nickel non-woven porous transport layers (PTL). A highly active cell can be combined with a cathodic HER catalyst, prepared by electrochemical deposition Ni-S on a stainless steel non-woven PTL.In single cell AEM water electrolysis using 1 M KOH-solution utilizing the prepared NiFe-LDH anode and Pt/C cathode, 2.7 A/cm² at 2 V were achieved, surpassing commercially available powder catalysts like NiFe-oxide. Comparative analysis of Ni-S cathode with NiFe-LDH, integrated into a membrane electrode assembly demonstrated superior AEM-WE performance, outperforming the mentioned platinum on carbon catalysts. Electrochemical impedance spectra indicated higher charge transfer activity of Ni-S cathode compared to Pt/C. Importantly, the electrodes prepared in this study exhibited stability under accelerated electrochemical stress tests for 1000 cycles.These approaches provide a simple, inexpensive, scalable and therefore industry-relevant fabrication method with improved active areas and excellent catalytic activity during AEM water electrolysis. Figure 1

Bias-Free Environmental Pollutants Conversion By Integrating Bi-Functional Catalyst with Dual Organic Photoelectrode System

The rapid increase in human activities has led to an oversupply of nitrate and glycerol, emerging as significant environmental pollutants, disrupting the delicate balance of the global nitrogen and carbon cycles. Addressing this challenge, photoelectrochemical (PEC) conversion harnesses solar energy to effectively convert excess nitrate into ammonia and surplus glycerol into high-value carbon compounds, thereby mitigating their environmental impact and enhancing both environmental sustainability and cost-effectiveness. Notably, among the resulting products, ammonia and formic acid have garnered attention as prominent carriers for hydrogen storage and transportation, given their high hydrogen storage capacity relative to their mass and volume, further emphasizing the importance of PEC conversion. Organic semiconductor materials, characterized by high photovoltage and photocurrent density, present promising prospects for producing efficient photoelectrodes. However, their utility has been hindered by poor stability in aqueous electrolytes. In this study, we address this challenge by employing an encapsulation method to fabricate stable organic semiconductor-based photocathodes and photoanodes operable in aqueous electrolytes. Moreover, we have devised a novel photoelectrochemical system capable of operating without external voltage, facilitated by a dual photoelectrode system. The Ni-Fe-P alloy, with its unique combination of bimetallic and phosphide properties, stands out as a promising non-noble metal catalyst. Nickel facilitates hydrogenation and enhances product selectivity, while iron boosts initial adsorption and reaction activity. Phosphorus disrupts electron distribution, creating additional active sites for intermediate adsorption. This multifaceted catalytic activity enables the Ni-Fe-P alloy to function effectively in both nitrate reduction and glycerol oxidation simultaneously. By integrating a bifunctional Ni-Fe-P catalyst into our dual photoelectrode system, we've achieved significant progress. This system efficiently reduces nitrates and converts glycerol, yielding valuable hydrogen carriers like ammonia and formic acid. Importantly, we've attained photocurrent densities of several mA cm⁻² without the need for bias. This breakthrough marks a robust and effective development in photoelectrochemical systems, addressing both environmental remediation and hydrogen carrier production challenges.

Development of Barium-Modified Anodes for Anode-Supported Solid Oxide Fuel Cells Fueled with Ammonia

Solid oxide fuel cells (SOFCs) have attracted significant attention due to their high power generation efficiency and low pollutant emissions. Owing to the use of solid oxide electrolytes, SOFCs are usually operated at high temperatures of 600–800 oC, leading to favorable fuel flexibility. Although alternative fuels such as hydrocarbon fuels are superior to pure hydrogen in terms of storage, transportation, and energy density, by-products from the fuels, as exemplified by carbon, will deteriorate the performance and stability of anodes. Ammonia is promising as a carbon-free fuel for SOFCs because of its low cost, high hydrogen content and volumetric energy density, and ease in liquefaction and transportation under mild conditions. In ammonia-fueled SOFCs, the following reactions occur on the anode. 2NH3 → N2 + 3H2 (1) H2 + O2− → H2O + 2e− (2)Ammonia is decomposed to form nitrogen and hydrogen (1) and then the produced hydrogen is electrochemically oxidized (2). Thus, the anode material has to be active for ammonia decomposition as well as electrochemical hydrogen oxidation. The conventional Ni–YSZ electrode, however, is known to have low activity for ammonia decomposition. Therefore, it is necessary to enhance the catalytic activity of Ni–YSZ-based anode. It has been reported that the addition of basic components to Ni-based catalysts improve the ammonia decomposition activity. In this study, then, we modified the anode of a commercial anode-supported SOFC button cell (Elcogen, ASC–400B) with barium components by dropping a solution containing barium salts onto the electrode. The effect of additive component on the cell performance was evaluated. An aqueous solution of 2.0 M Ba(CH3COO)2–0.7 M C2H5NO2 was dropped onto the anode of anode-supported cell, followed by the heat-treatment at 800 oC for 2 h. This series of process was repeated several times so that desired amounts of barium component were loaded. Performances of the as-received cell and the fabricated cells were evaluated under hydrogen- and ammonia-containing fuels at 600–750 oC. For the as-received cell, cell performances were comparable in both fuels at 700 oC, indicating that the ammonia decomposition proceeded over the anode, while the performance were much different between H2 fuel and NH3 fuel at lower temperatures. On the other hand, comparable performances were obtained under both fuels at all the temperatures investigated. This suggested that the barium component promoted the ammonia decomposition sufficiently over the anode even at 600 oC. This work was supported by JST SICORP Program (Grant Number: JPMJSC2122).

Oxidative Desorption Behavior of Sulfur Species from Pt and Pt Based Alloy Single Crystal Surfaces

Pt and Pt-based alloys are the most widely used electrocatalyst for polymer electrolyte membrane fuel cells (PEMFCs) because of their very high hydrogen oxidation and oxygen reduction activities. However, trace amounts of S species in hydrogen fuel and air, especially in long tunnels and volcanic areas, often strongly adsorb on the Pt and Pt-based alloy surfaces, resulting in reduced electrochemically active surface area (S poisoning). Thus, understanding of adsorption/desorption behavior of S species at Pt and Pt-based alloy surfaces is very important to mitigate such S poisoning. In the present study, oxidative desorption behavior of S species from well-defined Pt and Pt-based alloy single crystal surfaces in acidic aqueous solutions were studied by electrochemical measurements, x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculation.Pt and Pt-based alloy single crystal surfaces were annealed by induction heating method [1, 2, 3] at various temperatures for 1 h under the flowing of Ar and H2 mixed gas, followed by cooling under the Ar and H2 flow for 7 min. The surfaces were then immersed in an aqueous solution of 1 mM Na2S for 1 h to yield S-adsorbed surfaces. After rinsing with water, electrochemical measurements were carried out in an aqueous solution of 0.1 M HClO4, followed by XPS measurements.Bare Pt and Pt-based alloy single crystal surfaces showed characteristic current responses corresponding to adsorption/desorption of hydrogen and hydroxyl species as previously reported. After immersing in the 1 mM Na2S solution, those characteristic current responses completely disappeared due to the blocking of adsorbed elemental S species as evidenced by XPS. However, those characteristic current responses gradually recovered by repeating the potential cycles in the potential range between 0 V and 0.8 V or more positive, due to the oxidative desorption of S species. The recovery factor significantly depends on the face orientation, alloying foreign metal and surface modification. Among the Pt(111), Pt(110) and Pt(100) surfaces, Pt(111) surface showed the highest S oxidation capability. The S oxidation capability was further accelerated by alloying with several transition metals and coating with metal oxides. The details will be discussed.

Reduced Graphene Oxide Supported MoSxSe2-X Bifunctional Electrocatalysts for Electrochemical Ammonia Production from Nitrate

Ammonia (NH₃) holds significant importance across various human activities, finding applications in fertilizers, pharmaceuticals, and carbon-free energy fuel. Traditionally, NH₃ production relies on the energy-intensive Haber-Bosch process, leading to substantial CO₂ emissions. As an alternative, there's growing interest in electrochemical NH₃ production. The electrochemical nitrate reduction reaction (NO₃RR) is particularly promising due to its low energy barrier, high nitrogen source solubility, and high activity. Molybdenum dichalcogenides (Mo-based TMDs) have emerged as catalysts for electrochemical NH₃ production, leveraging their 2D structure, large surface area, and tunable electrical properties. However, Mo-based TMDs having 2H crystal structure face challenges like low electrical conductivity and high hydrogen evolution reaction (HER) activity, which competes with NH₃ production. To address this, we developed various 1T-MoSxSe2-x/rGO electrocatalysts. These catalysts exhibited a yield rate exceeding 3511.9 μg h-1 cm-2 (at -0.6 V vs. RHE) and a 70 % faradaic efficiency (at -0.2 V vs. RHE) in a 1 M KOH and 0.1 M NaNO₃ solution. And their bifunctional properties (Oxygen evolution reaction, OER) show a low overpotential of 338.8 mV at 10 mA. Our research aims to enhance NO3RR under ambient conditions and investigate the potential of bifunctional properties (OER) for the commercialization of electrochemical NH₃ production.

Corrosion Failure Analysis of Peak Load Boiler Using Landfill Gas

A peak load boiler using landfill gas as a fuel is one of the heat production facilities of a district heating system. It undergoes frequent start-and-stop operations for flexible heat supply. Landfill gas is refining gas produced from local landfills through a series of processes. Methane and carbon dioxide are the main elements, and volatile organic compounds (VOCs), hydrogen sulfide and halides are the minor elements. In this study, the causative factors of corrosion damage in the peak load boiler using landfill gas were identified, and a lifetime of selected materials under the corrosive environment was evaluated. The higher the concentration of acid ions and water vapor, the higher the dew point temperature is formed. It is concluded that the high hydrogen sulfide component in the landfill gas and the humidity in the facility resulted in an increase in the dew point formation temperature, from which the corrosion damage led to a leakage of boiler tube.

(Invited) Low Contact Resistance on Buried Interfaces in Oxide Thin-Film Transistors by Selective-Area Reduction Using Hydrogenation Catalyst Electrode

As the focus on amorphous oxide semiconductor (AOS) in memory applications deepens, there is a push for higher packing densities and more efficient read-write efficiencies, leading to increasingly complex AOS transistor structures with dimensions scaled down to the nanometer size. In pursuit of high density for AOS-based dynamic random-access memory (DRAM), 3D-stacked vertical IGZO transistor devices have been employed, wherein the contact interfaces of these vertical devices are buried and located internally within the device, and these vertical or buried interfaces are prone to causing contact issues. However, conventional methods to addressing contact resistance in thin-film transistors (TFTs) used for flat-panel displays are not applicable to buried interfaces. The development of novel methods to resolve this issue is a current challenge for the future development of complex structured AOS memory devices.In this work, the contact resistance of a-IGZO TFT was reduced by three orders of magnitude by utilizing hydrogenation catalyst electrodes for a selective area reduction reaction at the interface and constructing a hydrogen transfer pathway1. The key to effective hydrogenation on the internally buried interface is the selection of the optimal catalyst metal electrode and passivation materials that satisfy the following requirements. 1) High hydrogen diffusion rate and moderate hydrogen solubility for reversible hydrogen transfer. 2) Catalytic hydrogen dissociation to highly active H0 atoms on/in the metal electrode for low-temperature reaction [Fig. 1(a)]. 3) Dense oxide passivation layer with hydrogen tolerant electronic structure to hydrogen, in which a shallower CBM than the charge transition level of E(H+/H−), to isolate the effective channel from hydrogen. Pd was selected as the best electrode for this strategy owing to its flexible lattice and unique properties of hydrogen permeability without brittleness to hydrogen. Also, amorphous Zn–Si–O (ZSO x ), which can be easily deposited by sputtering, was used as the passivation layer.Detection through hard X-ray photoelectron spectroscopy indicates that the high reactivity of H0 reduces metal oxides at the interface, forming a metallic interface layer. Fig. 1(b) shows the hydrogen annealing condition dependence of the contact resistance and effective channel length deviation estimated by TLM measurements. By optimizing hydrogen annealing conditions, the company succeeded in achieving both a small effective channel length deviation of ~40 nm and contact resistance that was reduced by approximately three orders of magnitude. The field-effect mobility was enhanced from 3.2 to ~20 cm2 V–1 s–1 as a consequent effect of the improved contact resistance. Furthermore, as shown in Fig. 1(c), the prepared a-IGZO TFTs also demonstrated excellent bias-stability, further proving the reliability of using catalytic electrodes and hydrogen tolerant passivation layer in the process.

Kinetically Accelerating Ni and C Dual Active Sites Via Pyrrolic-N for Water Dissociation and Alkaline Hydrogen Production

Green hydrogen, which is one of the most promising solutions to environmental issues and energy crises, can be produced through water electrolysis using renewable electricity as eco-friendly and sustainable route. However, the cathodic hydrogen evolution reaction (HER) has been a subject of extensive research due to the slow kinetics of proton-coupled electron transfer, which lowers the overall efficiency. In particular, the rate of HER in alkaline media appears two to three times slower than that in acidic or neutral media. This is because in order to form adsorbed hydrogen, additional water dissociation must first proceed in the Volmer step (H2O + e- → Had + OH-), followed by the coupling of adsorbed hydrogen in the Heyrovsky or Tafel steps (H2O + Had + e- → H2 + OH- / Had + Had → H2). The hydrogen adsorption-free energy (ΔGH*) has traditionally been considered the primary factor influencing the kinetics of the HER at the Heyrovsky and Tafel steps. However, it is important to note that sufficient proton supply to the catalytic sites relies on water adsorption capacity and the ability to cleave the HO-H bond. As a results, a proper strategy for achieving high hydrogen coverage (M-Had) must incorporate both water dissociation and hydrogen combination. Unfortunately, the activation of O- and H- containing intermediates for water dissociation and proton combination requires different catalytic properties, which highly presents a challenge. Therefore, it is crucial to understand the correlation between the catalytic chemical state, adsorption energy of intermediate species (H2O, OH, Had), and the kinetic mechanism of the HER from a theoretical standpoint.Pt-based materials are currently recognized as the most efficient catalysts for the HER. However, they exhibit unsatisfactory intrinsic kinetics under alkaline conditions due to the slow dissociation rate of water caused by the additional energy barrier of HO-H bond dissociation. Furthermore, their scarcity and high price limit their industrial applications. As an alternative, Ni-based materials are considered promising catalysts due to their Pt-like hydrogen adsorption-free energy and the possibility of optimizing water dissociation through chemical state modulation. Recent studies have shown that modulating the surface electronic structure of Ni-based materials through synergistic interactions is an effective way to activate intermediates for alkaline HER. However, most studies on chemical state reorganization focus on a single site, which underestimates the mechanism-based kinetics and makes it difficult to simultaneously control water dissociation and proton adsorption. Therefore, introducing dual active sites that optimize O- and H- affinity independently can be an effective strategy to reduce the energy barrier for Volmer, Heyrovsky and Tafel steps. Moreover, considering the proton pathway within Ni-based catalysts to accelerate alkaline HER kinetics, it is essential to simultaneously govern thermodynamics and kinetics through a kinetic-oriented design.In this study, we present a novel design approach that focuses on alkaline HER kinetics by incorporating dual active sites using Ni nanoparticles embedded in pyrrolic-N-rich carbon nanoplates (Ni@NCP), resulting in robust alkaline HER kinetics. The introduction of N-functional-rich polydopamine (PDA) serves two purposes: it ensures the uniform distribution of reduced Ni nanoparticles within the carbon substrate, and it enriches the ratio of pyrrolic-N in defective carbon, thereby regulating the properties of the Ni metal and the C atoms near the pyrrolic-N. Consequently, the Ni@NCP catalyst exhibits remarkable alkaline HER performance, with a low overpotential of 42 mV at a current density of 10 mA/cm2 and a Tafel slope of 94.9 mV/dec. These results outperform those of previously reported transition metal-based or single metal phase-based HER electrocatalysts. Further validation through the utilization of in-situ/operando Surface Enhanced Raman Spectroscopy (SERS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations confirmed that the alkaline HER kinetics were significantly optimized by the pyrrolic-N-induced asymmetric electronic distribution, specifically by (ⅰ) shifting the d-band center (εd ) of the nearby Ni atoms towards the Fermi energy level to enhance the interaction with -H in H2O molecules and optimize the proton adsorption energy, (ⅱ) increasing the adsorption affinity of nearby C atoms towards H2O and -OH to optimize H2O adsorption, and (ⅲ) elongating the HO-H bonds, facilitating bond cleavage, and promoting simultaneous proton supply into Ni atoms. The kinetic-oriented design of dual active sites significantly reduces the kinetic energy barrier during Volmer step of water dissociation, resulting in facilitates the supply of sufficient protons for accelerated alkaline HER kinetics, ultimately enhancing the overall catalytic activity. Moreover, in a two-electrode system with Ni@NCP as the cathode for water electrolysis, Ni@NCP||IrO2 outperforms the commercial Pt/C||IrO2 system at the current density over 2.3 A/cm2, which shows superior potential for the practical application. Figure 1

The Performance of PEFC with Marimo-like Carbon Considering Relative Humidity

1.IntroductionThe Pt catalyst supported on carbon black (Pt/CB) is widely used as a catalyst for the polymer electrolyte fuel cell (PEFC). As an alternative carbon support to the CB, which is a type of particulate carbon, we have used Marimo-like carbon (MC) which is a type of fibrous carbon. MC has a spherical structure comprised of carbon nanofilaments (CNFs) radially grown from an oxidized diamond core 1). The CNFs in the MC have a cup-stack primary structure of graphene sheets; thus, the sheet edge can effectively function as a supporting site for the Pt catalyst. There are voids of several hundred nanometers between the CNFs of the MC. These voids are expected to improve the diffusion of hydrogen gas and air and the removal of produced water. The diffusivity of hydrogen gas and air and the removal of produced water are different between the MC and CB due to their structural differences. These differences in mass diffusivity changed the state of water management and the PEFC performance. In this study, the performance of a PEFC with Pt/MC while considering the relative humidity (RH) of the hydrogen gas and air were investigated.2.ExperimentalThe catalyst supports were CB and MC. MC was synthesized by thermal chemical vapor deposition (CVD). For the synthesis, methane (CH4) gas was used as the carbon source of the CNFs and Ni supported diamond oxide (Ni/O-dia.) was used as a growth catalyst. The Ni/O-dia. was contacted with the CH4 gas in a reactor rotating at 5 rpm. The CH4 gas was supplied at the flow rate of 1000 CCM for 3 hours. During this time, the rotary reactor was heated to 550°C. Pt/MC was synthesized by reducing Pt ions in a suspension with MC. Pt/CB was prepared as a commercial Pt nanoparticle supported on the CB. Nafion was used as the ionomer in this study. The catalyst ink was prepared by adding a Nafion dispersion to the Pt/MC and Pt/CB. The ionomer/carbon (I/C) ratio was 0.1 and 0.7 for the MC and CB, respectively 3). The catalyst layer (CL) was prepared by spraying the catalyst ink onto a 50 mm × 50 mm PTFE sheet. The membrane electrode assembly (MEA) was fabricated by transferring CL to the Nafion membrane by hot pressing. The PEFC performance was evaluated at the cell temperature of 80.0°C. Hydrogen gas and air were saturated at this temperature using a humidifier. Humidified hydrogen gas was supplied to the anode and humidified air was supplied to the cathode. The relative humidity of the hydrogen gas and air was controlled by the humidifier temperature.3.Results and discussionThe structure of the MC was observed by a scanning electron microscope (SEM). SEM images of the MC showed numerous CNFs. Voids of several hundred nanometers were observed between the CNFs. The Pt supporting state of the Pt/MC was observed by a transmission electron microscope (TEM). TEM images of the Pt/MC showed Pt supported on the surface of the CNFs.The PEFC performances of the Pt/MC and the Pt/CB were compared. At a high current density, the PEFC performance of the Pt/MC was higher than that of the Pt/CB. The PEFC performance in the high current density region consumed a large amount of hydrogen gas and air. This result was due to the high hydrogen gas and air diffusivity and the high removal of produced water from the MC.The relative humidity of the air was controlled from 20 to 100% RH by supplying it to a humidifier at a temperature of 42.7 to 80.0°C. The humidification conditions of the air affected the PEFC performance of both the Pt/MC and the Pt/CB. Under the low humidification condition, the PEFC performance was reduced due to the decrease in proton conductivity of the Nafion membrane. Under the high humidification conditions, the PEFC performance decreased due to flooding. The change in the PEFC performance under these humidifying conditions was particularly high by the MC.1) N. Hirata, et.al., RSC Adv., 11, 39216-39222 (2021)2) M. Eguchi, et.al., Jpn. J. Appl. Phys., 52, 06GD06 (2013)3) M. Eguchi, et.al., polymers, 4, 1645-1656 (2012)

The Contributions of Catalyst Layer Resistance on Overall Overpotentials in Anion Exchange Membrane Water Electrolyzers

Anion exchange membrane water electrolyzers (AEMWE) combine the benefits of traditional liquid alkaline (LAWE) and proton exchange membrane water electrolyzers (PEMWE), producing H2 at high current densities while allowing the use of low-cost, low-criticality PGM-free materials for catalysts and hardware. Advances in AEMWE performance have risen rapidly in recent decades, and research on AEMWEs has increased dramatically.1 However, despite significant component-level advances in catalysts and membranes,2,3 gaps remain to achieve performance parity with PEMWEs and the relative overpotentials of AEMWE remain high. Strategies are thus needed to understand, diagnose, and quantify the origins of overpotentials in AEMWEs and help bridge the gap between AEMWE and PEMWE performance.By utilizing Tafel analysis and electrochemical impedance spectroscopy, voltage breakdown analyses can be performed to decouple the origins of high overpotentials in electrolyzers. While such methods are used frequently in the literature to determine kinetic and Ohmic losses, voltage breakdown analyses are rarely performed beyond these contributions, even though other losses can often account for 100s of mVs (20-30% of non-thermodynamic losses). Recent works have demonstrated that catalyst layer resistances can be quantified in electrolyzers using transmission line theory for porous electrodes.4 To the best of our knowledge, however, this method has not yet been adapted to AEMWEs. Furthermore, differences in cell operation and performance (e.g., use of supporting electrolyte, high hydrogen evolution reaction overpotentials) leads to differences in the expected nature of catalyst layer resistances for these two technologies. There is therefore a need for AEMWE-specific methods to diagnose and quantify catalyst layer resistance.In this work, a method for determining catalyst layer resistance from transmission line theory for porous electrodes4 is adapted to AEMWE and applied to four anode catalyst materials tested in single-cell MEAs. Changes to the catalyst layer thickness, ionomer content, and electrolyte concentration reveal trends about the origins of catalyst layer resistances in AEMWE cells. Investigations of the anode transport layer show that this component introduces significant impedance, which thus must be considered for AEM diagnostics and performance optimization. Furthermore, the results suggest that discontinuities in electronic and ionic transport networks in the catalyst layer may explain discrepancies between idealized kinetic results from rotating disc electrode testing and those observed for MEAs. These results then inform the development of a model to understand and differentiate contributions from anode and cathode catalyst layers in AEMWEs. These results will ultimately allow for the design of more efficient catalyst layers, reducing overpotentials and facilitating AEM deployment commercially.[1] Volk, E. K. et al., EES Catalysis 2024, [2] Chen, N. et al., Trends Chem. 2022, [3] Plevová, M. et al., J. Power Sources 2021, [4] Padgett, E. et al., J. Electrochem. Soc. 2023

Effect of KOH Concentration on Viscoelastic and Conformational Changes of Xanthan Gum-Based Hydrogel Electrolytes

Introduction Lithium-ion batteries (LIBs) are currently the most practical rechargeable batteries, but their energy density is insufficient for applications such as electric vehicles and power storage. Moreover, the safety issues for LIBs have not yet been completely resolved. Therefore, research on the development of next-generation batteries with high safety and high energy density is being promoted. Recently, aqueous rechargeable batteries using zinc as the negative electrode has attracted considerable attention because zinc has many attractive features: low standard potential (−0.76 V vs. SHE), high hydrogen overpotential, high gravimetric and volumetric theoretical capacities (820 mAh g-1, 5855 mAh cm-3), and low cost. However, for the implementation of aqueous rechargeable zinc batteries, there are some serious issues such as zinc dendrite formation, shape change and side reactions (hydrogen evolution, corrosion, passivation, etc.) at the negative electrode. We have demonstrated the effectiveness of crosslinked polyacrylate-based hydrogel electrolytes (HEs) as an alternative to aqueous alkaline solutions to improve these issues (1). We have recently become interested in physical gels in which the host polymer is cross-linked by intermolecular interactions such as hydrogen and ionic bonding, and prepared new HEs by mixing xanthan gum (XG), one of polysaccharides, as host polymer and aqueous KOH solutions. The XG-based HEs showed ionic conductivity comparable to the corresponding alkaline aqueous solutions. However, the details of the influence of the gel structure on the diffusion of zincate in the gel and the deposition and dissolution of zinc at the electrode/hydrogel electrolyte interface remain unclear. In this study, the viscoelasticity of XG-based HEs with different KOH concentrations and XG contents were evaluated to investigate how the gel structure, and in particular the conformation of XG, changes with different KOH concentrations and XG contents. Experimental HEs were prepared by mixing various concentrations of aqueous KOH solutions and XG powders with stirring. A rheometer was used to measure the viscoelasticity of the prepared HEs. In addition, structural changes in XG in the HEs were investigated by Infra-red (IR) spectroscopy and gel permeation chromatography (GPC). Results and Discussion Change in viscosity, which was measured with a rheometer, with the concentration of KOH for the HEs with 0.05, 0.1 and 0.3 g mL-1 XG is shown in Fig. 1. The XG structure consists of a β-glucan main chain with long side chains (molecular weight about 600) consisting of three molecules of monosaccharide attached in an orderly fashion. In water, XG molecules exist in a state where the individual main chains are elongated due to electrostatic repulsion between COO- groups in the side chains. In aqueous KOH solutions, as the KOH concentration increases, the negative charges of COO- groups on the side chains are shielded by the interaction with K+, reducing the electrostatic repulsion. As a result, the XG molecules become entangled, increasing viscosity. In Fig. 1, as expected, viscosity increased as KOH concentration increased up to 1 M. However, it decreased significantly above 1 M and was a minimum at 4 M. For the HE prepared by using 4 M KOH solution, GPC analysis suggested that some of the side chains were cleaved. This may cause the decrease in viscosity. When the KOH concentration was higher than 4 M, the viscosity increased again, as can be seen from Fig. 1. The analysis of IR spectra for HEs exhibited that the structure of XG molecules scarcely changed as the KOH concentration increased from 4 M to 7 M. Therefore, the increase in viscosity at KOH concentrations above 4 M is probably due to the salting out.This work is based on results obtained from a project, JPNP21006, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Reference C. Iwakura, H. Murakami, S. Nohara, N. Furukawa, H. Inoue, J. Power Sources, 152, 291 (2005). Figure 1

Understanding Structure Differences of Iridium Oxides Depends on Loading in Proton Exchange Membrane Electrolyzers

Proton exchange membrane water electrolyzers (PEMWEs) have drawn attention among various hydrogen production technologies due to their zero-emission, high conversion efficiency, high hydrogen purity (>99.99%), and quick response under dynamic operation.1,2 With these auspicious characteristics in PEMWEs, they are believed to produce 40 % of green hydrogen by 2050 among all electrolyzer technologies. Nonetheless, many bottlenecks within PEMWEs still hinder their broader commercialization. Iridium oxide is the most widely used oxygen evolution reaction (OER) electrocatalyst at the anode. Moreover, this catalyst occupies the biggest portion (26–47%) of the overall cost of PEMWE systems, mostly due to the scarcity of iridium.3 Commercial iridium oxide catalysts are generally two types depending on the material structure: amorphous IrOx and crystalline IrO2. The trade-off relationship exists in catalytic activity vs. stability between amorphous and crystalline IrOx catalysts.4–6 To overcome these problems, fundamental studies of iridium oxide need to be conducted to reduce catalyst loading while maintaining high performance.Herein, we report the new iridium oxide catalysts (amorphous IrOx, crystalline IrO2, Ishifuku Metal) for the first time. These new iridium oxide catalysts are physically and electrochemically characterized. To be specific, we confirm the distinct characteristics of each catalyst using scanning electron microscopy (SEM), focused ion beam SEM (FIB-SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) analysis with nitrogen adsorption isotherm, Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). As a result, the crystalline IrO2 has a unique morphology with grown needles onto catalyst particles thereby the BET specific surface area of crystalline IrO2 (~110 m2 g-1) is over two times higher than amorphous IrOx (~50 m2 g-1). Electrochemical performance is evaluated for varied catalyst loadings of membrane electrode assembly (MEA). The catalyst loadings (0.10, 0.26, 0.35, and 0.85 mgIrOx cm-2) for both anode catalysts were prepared. The CV results of amorphous IrOx exhibit unique redox peaks under specific voltage (~0.8 and ~1.2 V vs. RHE), which indicates the transition of oxidation state. These peaks develop with CV cycling and become fully developed after 100 cycles, indicating that the surface of the catalyst takes some time to activate. On the other hand, crystalline IrO2 shows no specific redox peaks but rather has a double-layer capacitance under lower voltage (<0.5 V vs. RHE). Figure 1 shows 1.92 V (amorphous) and 1.94 V (crystalline) at 5 A cm-2 for 0.85 mg cm-2 loading, respectively. Both catalysts showed relatively low Tafel slopes of 43.8 mV dec-1 (amorphous IrOx) and 53.7 mV dec-1 (crystalline IrO2). This presentation will correlate the electrochemical performance described here to the structural properties of these two types of IrOx catalysts. Figure 1. Polarization curve for prepared iridium oxide catalysts (amorphous IrOx and crystalline IrO2). Both cells have anode loadings of 0.85 mg cm-2, cell temperature at 60 °C, 10 sccm for H2O flow rate at the anode, and dry for the cathode.

High efficiency photocatalytic hydrogen evolution by black phosphorus quantum dots decorated 1D g-C3N4 nanotubes

Bare g-C3N4 (CN) encounters substantial charge recombination with strong fluorescence, which is detrimental to the photocatalytic reactions. In this work, g-C3N4 is curved into nanotubes then combined with black phosphorus quantum dots (BPQDs). The BPQDs decorated tubular CN (BPTCN) exhibits a stable and high photocatalytic hydrogen evolution rate of 507.51 μmolh−1g−1 under visible irradiation, which is four times higher than that of pure TCN. The apparent quantum yield (AQY) at 420 nm of BPTCN reaches 2.58%. The excellent photocatalytic ability of the BPTCN is attributed the suppressed recombination of electron-hole pair and improved carrier transport efficiency, which are introduced by the 1D tubular structure and the band alignment of the BPTCN heterojunction.

Development and optimization of metal silicide EUV pellicle for 400W EUV lithography

In the extreme ultraviolet lithography (EUVL) process, extreme ultraviolet (EUV) pellicles serve as thin, transparent membranes that shield the photomask (reticle) from particle contamination, thereby preserving photomask pattern integrity, reducing chip failure risks, and enhancing production yields. The production of EUV pellicles is highly challenging due to their mechanical fragility at nanometer-scale thicknesses and the need to endure the rigorous conditions of the EUVL environment, which include high temperatures and hydrogen radicals. Consequently, extensive research has been conducted on a variety of materials, such as carbon-based and silicon-based substances, for the development of EUV pellicles. This study explores the feasibility of implementing metal silicide (MeSix) pellicles for high-power EUVL applications. We successfully fabricated MeSixpellicles in two dimensions: a 10 mm × 10 mm sample and a full-size 110 mm × 144 mm pellicle. We then evaluated their optical, mechanical, thermal, and chemical properties, as well as their lifespan. The pellicles demonstrated over 90% transmittance and less than 0.04% reflectance. The films exhibited a deflection of 300μm under a 2 Pa differential pressure and an ultimate tensile strength exceeding 2 GPa. The thermal emissivity was measured at 0.3. Additionally, the durability of the pellicles was validated through exposure to 20,000 wafers using a 400 W EUV power (offline test: 20 W cm-2). The transmittance variations of the pellicles were evaluated by comparing the measurements obtained before and after exposure to 400 W EUV power.

Self-supported bifunctional P–CoSe/NF electrodes for high efficiency and durability hydrogen production coupled with sulfion valorization

Integrating sulfide oxidation reaction (SOR) with hydrogen evolution reaction (HER) by electrochemical means to simultaneously valorize sulfion and produce hydrogen is an efficient cleaner production method. Currently, we reported on the fabrication of one succulent-like phosphorus-doped transition metal selenide bifunctional catalyst supported on nickel foam (P–CoSe/NF) for SOR and HER. The unique structure has a significant surface area that allows many active sites to be exposed, enabling the catalyst to have an excellent activity up to 100 mA cm−2 at only 0.362 V. The H2 Faraday efficiency reaches 97.4% and the rate of sulfur evolution is 26.24 mg h−1. The durability test demonstrates that the bifunctional catalyst possesses excellent anti-sulfur properties. The Density Functional Theory calculations demonstrate that phosphorus as a dopant is believed to confer an optimal electronic structure and local coordination environment by tuning d electron number. The calculate S8∗ to S8 was confirmed to have a low energy barrier, indicating the self-cleaning tendency caused by phosphorus doping. This work presents a promising approach utilizing anti-sulfur single-atom-doped transition metal selenide catalysts in electrochemical reaction, representing a significant advancement in achieving low-cost and high value-added using waste resources.

Comparative fracture analysis of API X52M and X52MH steels in high pressure hydrogen

Hydrogen embrittlement (HE) threatens the safety of hydrogen transportation pipelines. This study investigates HE susceptibility in X52M and X52MH steels, intended for hydrogen transport. Slow strain rate tensile (SSRT) tests are conducted in N₂ and H₂ at 6.3 MPa, with fracture surfaces analyzed using SEM and 3D X-ray micro-CT. Results reveal that X52MH steel is more susceptible to HE than X52M, attributed to its ferrite/bainite (F/B) duplex-phase microstructure, unlike the acicular ferrite (AF) structure of X52M. Segregation of Cu, Cr, and Ni in X52MH also promotes crack initiation and propagation, as hydrogen-induced cracks on the specimen surface and localised concentrations at the F/B interface from uncoordinated deformation increase HE susceptibility in X52MH.

Influence of human activities on soil microbial diversity, carbon sequestration, and resilience in Central African Forest Ecosystems

While tropical forests serve as critical carbon sinks with high biodiversity, they face increasing threats from deforestation, agriculture, and oil exploitation. This paper explores the relationships between soil bacterial and fungal community structure and diversity, soil properties, and major environmental challenges-including climate change, land degradation, biodiversity loss, and pollution in the mixed-species plantations featuring nitrogen-fixing species. Increased soil carbon storage observed in acacia and eucalyptus plantations may be influenced by the prevalence of Actinobacteria, which plays a critical role in organic matter decomposition. The dominance of Ascomycota within the fungal community appears to support ecosystem stability after environmental disturbances. High sulphur concentrations or hydrogen sulfide (H₂S) emissions promote Actinobacteria growth but, conversely, reduce Ascomycota prevalence. Both acacia and eucalyptus plantations enhance soil resilience to climate and land-use changes through increased carbon storage and other co-benefits. However, oil exploitation activities releasing H₂S emissions may compromise the ability of these mixed-species plantations to withstand environmental stresses, with potential long-term impacts on soil health and ecosystem function. This article underscores the need for sustainable practices to support soil health and ecosystem stability. It also advocates for further interdisciplinary research to understand the broader impacts of anthropogenic disturbances on forest ecosystem functions and resilience.

A Strongly Coupled 1T'-ReSe2@2H-MoSe2 van der Waals Heterostructure for Efficient Electrocatalytic Hydrogen Evolution at High Current Densities.

Developing efficient and durable non-noble metal electrocatalysts for high current-density hydrogen evolution reactions (HER) is a pressing requirement for commercial industrial electrolyzers. In this study, a vertical 1T'-ReSe2@2H-MoSe2 van der Waals heterostructure was developed through interface engineering to enhance the advantages of each component and expose numerous active sites. Experimental investigations and density functional theory calculations demonstrate significant electronic coupling at the interface between 1T'-ReSe2 and 2H-MoSe2, with suitable Gibbs free energy for hydrogen adsorption. The 1T'-ReSe2@2H-MoSe2 heterostructure catalyst achieves high current density HER with low overpotentials of 191 mV to generate up to 800 mA/cm2 in 0.5 M H2SO4, outperforming commercial 5 % Pt/C catalysts. Moreover, this catalyst exhibits rapid reaction kinetics and long-term durability, illustrating a successful approach to designing efficient heterostructure electrocatalysts for hydrogen production through interface engineering.

Unveiling S-scheme synergies: Synthesis and photocatalytic advancement of Au NRs-infused Fe₂O₃QDs/g-C₃N₄ hybrids–A new frontier in visible light-driven water splitting

This study presents a novel approach for the design and synthesis of gold nanorods (Au NRs) integrated into Fe₂O₃ quantum dots (QDs) and g-C₃N₄ nanosheets, targeting enhanced photocatalytic performance for visible-light-driven water splitting. The Au NRs, synthesized through a controlled growth method and subsequently purified and functionalized, were incorporated into Fe₂O₃ QDs/g-C₃N₄ hybrids via low-temperature calcination. Characterization of the composites revealed uniform dispersion of the Au NRs within the Fe₂O₃ QDs/g-C₃N₄ matrix, facilitating optimal light absorption and charge carrier separation. Photocatalytic experiments demonstrated that the Au NRs significantly enhanced the photocatalytic efficiency of the Fe₂O₃ QDs/g-C₃N₄ hybrid. The Au NRs@Fe₂O₃ QDs/g-C₃N₄ composite achieved a remarkable 99.4 % degradation of methylene blue (MB) within 90 min under visible light, while maintaining a high hydrogen evolution rate of 368.16 mmol·g⁻¹·h⁻¹ over 3 h. The enhanced performance is attributed to the unique S-scheme heterojunction between Au NRs, Fe₂O₃ QDs, and g-C₃N₄, which promotes efficient charge separation, extended light absorption, and accelerated redox reactions. This work demonstrates the potential of engineered Au NRs@Fe₂O₃ QDs/g-C₃N₄ nanohybrids as an efficient photocatalyst for visible-light-driven hydrogen production and environmental remediation, offering a promising pathway toward sustainable energy solutions.

Exploring Hydrogen–Diesel Dual Fuel Combustion in a Light-Duty Engine: A Numerical Investigation

Dual fuel combustion has gained attention as a cost-effective solution for reducing the pollutant emissions of internal combustion engines. The typical approach is combining a conventional high-reactivity fossil fuel (diesel fuel) with a sustainable low-reactivity fuel, such as bio-methane, ethanol, or green hydrogen. The last one is particularly interesting, as in theory it produces only water and NOx when it burns. However, integrating hydrogen into stock diesel engines is far from trivial due to a number of theoretical and practical challenges, mainly related to the control of combustion at different loads and speeds. The use of 3D-CFD simulation, supported by experimental data, appears to be the most effective way to address these issues. This study investigates the hydrogen-diesel dual fuel concept implemented with minimum modifications in a light-duty diesel engine (2.8 L, 4-cylinder, direct injection with common rail), considering two operating points representing typical partial and full load conditions for a light commercial vehicle or an industrial engine. The numerical analysis explores the effects of progressively replacing diesel fuel with hydrogen, up to 80% of the total energy input. The goal is to assess how this substitution affects engine performance and combustion characteristics. The results show that a moderate hydrogen substitution improves brake thermal efficiency, while higher substitution rates present quite a severe challenge. To address these issues, the diesel fuel injection strategy is optimized under dual fuel operation. The research findings are promising, but they also indicate that further investigations are needed at high hydrogen substitution rates in order to exploit the potential of the concept.