Hydrogen Generation Technologies Research Articles

Functional Ionomer Gradients in Anode Catalyst Layers for Low Temperature PEM Water Electrolysis

Water electrolysis is a crucial technology for large-scale hydrogen generation, that is required for the transition to a fossil fuel-free energy system. Even though water electrolysis systems are already deployed in a limited capacity, the technology is largely constrained to liquid alkaline electrolysis. Proton exchange membrane (PEM) electrolysis could pose an alternative but it is still hindered by high investment costs, in-part due to its reliance on scarce noble-metal catalysts. Alternative structural designs of the anode catalyst layer (CL) could reduce Iridium loading of the whole system and thus accelerate its wide-spread application. In fuel cell research, it was already reported that a multi-layer design with varied ionomer content enhances performance of the CL and in-turn lowers required catalyst loading.[1,2,3]In this study, a gradient design for ionomer content is employed for anode CLs for the application in PEM water electrolysis. CLs are coated in a stacked multi-layer design via ultrasonic spray coating of Iridium/Nafion® suspensions. The target ionomer loadings (10 and 30 wt.%) are confirmed by a combination of thermo-gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The coating process yields homogenously loaded reference CLs as well as through-plane graded CLs with the desired ionomer loading. Additionally, scanning electron microscopy (SEM) in conjunction with energy dispersive spectroscopy (EDS) shows equal CL thickness across all ionomer loadings and spatially differentiated Nafion® content throughout the CLs thickness. Electrochemical characterizations are carried out in an electrolysis-adapted gas diffusion electrode (GDE) half-cell setup to allow for quick examination and prototyping of produced layers. Differences in electrochemical performance of these layers can be observed with one gradient design CL showing reduced overpotential across all current densities compared to the homogenous CLs. In-particular a high ionomer loading near the membrane improves performance, most likely due to increased proton conduction to the membrane and higher available pore volume near the porous transport layer.Further analysis is performed on electrochemical studies to deepen the understanding of the role of ionomer in anodic PEM water electrolysis CLs. Particularly, the investigation of protonic and electric conductivity through the CL is of interest, because this parameter is most influenced by ionomer loading.[4]

Gasification of lignite from Polish coal mine to hydrogen-rich gas

The efforts of the world research activities involved in clean coal technologies development focus to a considerable extent on integrated hydrogen and power generation technologies based on coal gasification. As an alternative to combustion processes, gasification offers increased efficiency, lower negative environmental impact as well as wider application range of the main product—synthesis gas—in power generation and chemical syntheses. In order to select the most optimal lignite for the purpose of gasification, it is necessary to determine coal reactivity, the key parameter characterizing how fast the fuel reacts with the gasifying medium and controlling its process ability in thermochemical conversion to energy and/or energy carriers. This paper presents the experimental results of oxygen/steam gasification of lignite coal char in a fixed bed reactor under atmospheric pressure and at the temperature of 700, 800 and 900 °C; the samples come from an open pit lignite mine in the southwest of Poland. The effectiveness of the gasification process was tested in terms of the total gas and hydrogen yields, gas composition, carbon conversion rate and chars reactivity.

Excellent Catalytic Performance of ISOBAM Stabilized Co/Fe Colloidal Catalysts toward KBH4 Hydrolysis

Recently, developing a cost-effective and high-performance catalyst is regarded as an urgent priority for hydrogen generation technology. In this work, ISOBAM-104 stabilized Co/Fe colloidal catalysts were prepared via a co-reduction method and used for the hydrogen generation from KBH4 hydrolysis. The obtained ISOBAM-104 stabilized Co10Fe90 colloidal catalysts exhibit an outstanding catalytic activity of 37,900 mL-H2 min−1 g-Co−1, which is far higher than that of Fe or Co monometallic nanoparticles (MNPs). The apparent activation energy (Ea) of the as-prepared Co10Fe90 colloidal catalysts is only 14.6 ± 0.7 kJ mol−1, which is much lower than that of previous reported noble metal-based catalysts. The X-ray photoelectron spectroscopy results and density functional theory calculations demonstrate that the electron transfer between Fe and Co atoms is beneficial for the catalytic hydrolysis of KBH4.

An integrated solar energy, wastewater treatment and desalination plant for hydrogen and freshwater production

In this paper, a cost analysis study is undertaken for a commercial-scale hydrogen production and wastewater treatment plant, aiming to produce 1000 kg of hydrogen and treat 222 m3 of wastewater per day. The present cost-analysis model considers the technological and economic implications of central and forecourt hydrogen generation technologies. The model employs a photoelectrochemical solar concentrator system with heliostats/concentrators to concentrate solar irradiation at a 10:1 intensity ratio onto multi-junction photovoltaic/photoelectrochemical cell receivers submerged in an electrolyte reservoir and pressured to 20.7 bar. The photovoltaic cells are connected electrically to an electrolyte reserve and treat wastewater on the anode side using Fenton-like processes while generating H2 on the cathode side. Then, the chemical oxygen demand-free wastewater is delivered to the electrodialysis plant for desalination, acid and alkaline production purposes. The concentrated light driven photoelectrochemical H2 generation facility with a design capacity of 1,053 kg/day is used in the scale-up analyses. The cost of hydrogen is calculated to be $5.25/kg, excluding the profits obtained from the acid, alkaline and freshwater production. The yearly benefit from wastewater treatment is estimated as $81,030, respectively.

Oxygen Vacancy‐Enhanced Ternary Nickel‐Tungsten‐Cerium Metal Alloy‐Oxides for Efficient Alkaline Electrochemical Full Cell Water Splitting Using Anion Exchange Membrane

AbstractAlkaline water electrolysis is an attractive hydrogen generation technology with ultra‐high purity products and zero carbon emissions. However, the sluggish kinetics of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in both electrodes highly limits their applications. Benefiting from the abundant accessible active sites of the ternary alloy‐oxide structure formed on Ni foam directly, NiCeWOx shows superior HER and OER catalytic performances. The NiCeWOx‐2 (Ce/W ratio with 5/95) displays enhanced OER activity with an overpotential of 263 mV, while the NiCeWOx‐1 (Ce/W ratio with 79.8/21.2) shows better performance for alkaline HER with an overpotential of 130 mV at the current density of 10 mA cm−2. The catalysts show significant enhancement in terms of electrochemical reaction kinetics and conductivity compared to its original NiCeOx and NiWOx alloy phase. The efficient HER‐OER electrocatalytic performance is attributed to its unique alloyed oxygen vacancy structure‐property, which facilitates the diffusion of protons/OH− ions and significantly improves the electron conductivity for catalytic reactions. A low cell potential of 1.65 V is obtained at 10 mA cm−2 for NiCeWOx‐1||NiCeWOx‐2 in a full water‐splitting device in 1 M KOH electrolyzer with an anion exchange membrane. Also, NiCeWOx‐1||NiCeWOx‐2 exhibits extreme high stability after 24 h operation. This novel design utilizes low‐cost and robust electrocatalysts and will be useful for large‐scale alkaline water electrolysis.

Electrochemical hydrogen generation technology: Challenges in electrodes materials for a sustainable energy

AbstractForesee advanced and innovative strategies is a key approach and constitutes a cornerstone for accessing clean, affordable, and reliable energy to satisfy the world's increasing prosperity and economic growth. To this end, hydrogen energy technologies parade as promising sustainable solutions to the looming energy crisis at either the small or large industrial scale, which will enable to reduce significantly our dependence on conventional energy sources based on fossil fuels without increasing atmospheric CO2 levels. Water electrolysis with renewable energy is one of the best solutions to produce hydrogen without COx (CO and CO2) emissions. However, the practical realization of this elegant opportunity of paramount importance is facing several challenges, among which are: (i) the efficient design of cathode and anode catalytic materials exhibiting improved intrinsic and durable activity; (ii) the scale‐up of the system for the large‐scale hydrogen production through the electrochemical water splitting. This review puts these opportunities and challenges into a broad context, discusses the recent research and technological advances, and finally provides several pathways and guidelines that could inspire the development of groundbreaking electrochemical devices for hydrogen production. It also points out the materials design and preparation for the efficient electrochemical production of the molecular hydrogen in acidic and alkaline environments, from a simple electrolytic solution to the water splitting reaction, which is also considered in the process. Furthermore, the main technology keys for designing a reliable electrochemical system will be noticed.

Hydrogen Generation by Hydrolysis of MgH2-LiH Composite.

As a most promising material for hydrogen generation by hydrolysis, magnesium hydride (MgH2) is also trapped by its yielded byproduct Mg(OH)2 whose dense passivated layers prevent the further contact of intimal MgH2 with water. In this work, LiH, as a destroyer, has been added to promote the hydrogen properties of MgH2. The results demonstrate that even 3 wt % LiH was added into MgH2-G, the hydrogen generation yield can increase about 72% compared to the hydrogen generation yield of MgH2-G. The possible mechanism is that Mg2+ from the hydrolysis of MgH2 preferentially bound with OH− ions from the hydrolysis of LiH to form Mg(OH)2 precipitation, which is dispersed in water rather than coated on the surface of MgH2. Moreover, adding MgCl2 into hydrolysis solution, using ball milling technology, and increasing the hydrolysis temperature can make the hydrolysis rate higher and reaction process more complete. It is noted that a too high weight ratio of LiH with too high of a hydrolysis temperature will make the reaction too violent to be safe in the experiment. We determinate the best experimental condition is that the LiH ratio added into MgH2 is 3 wt %, the hydrolysis temperature is 60 °C, and the concentration of MgCl2 hydrating solution is 1 M. MgH2-LiH composite hydrogen generation technology can meet the needs of various types of hydrogen supply and has broad application prospects.

Porous hetero-structured nickel oxide/nickel phosphide nanosheets as bifunctional electrocatalyst for hydrogen production via urea electrolysis

Urea electrolysis is a promising hydrogen generation and urea-rich wastewaters treatment technology, which requires the development of highly active electrocatalysts. In this study, porous hetero-structured nanosheet electrocatalyst (NiO/Ni2P/NF), composed of crystalline NiO and Ni2P, is prepared via the in-situ acid etching and gas-phase phosphating method, and the obtained NiO/Ni2P/NF material is applied as efficient urea oxidation and hydrogen evolution catalyst for the overall splitting of urea-containing wastewaters. An electrolyzer containing NiO/Ni2P/NF||NiO/Ni2P/NF electrode pair in an alkaline urea aqueous solution requires a potential of just 1.457 V to reach a current density of 10 mA cm−2, lower than that of 1.490 V needed for a Pt/C/NF||RuO2/NF electrolyzer to operate under the same current density. The study demonstrates the synergistic effect between NiO/Ni2P nanosheets as well as their uniform pore structure formed by the Kirkendall effect, resulting in enhanced electrocatalytic performance in hydrogen production by urea electrolysis.

Roadmap to urban energy internet with wind electricity-natural gas nexus: Economic and environmental analysis

Electrolysis hydrogen generation technology is one of the feasible ways to alleviate the problem of wind electricity curtailment. One promising hydrogen value-added application is to blend hydrogen into the natural gas grid and sell it as the heat energy carrier. This paper aims to discuss the feasibility of a roadmap to urban energy internet with wind electricity-natural gas nexus. Firstly, a framework is raised to integrate wind electricity generation, electrolysis hydrogen generation, and hydrogen-natural gas blending systems. Secondly, a series of reasonable hydrogen supply profiles are provided based on annual electricity curtailment and realistic natural gas scheduling. Then, an energy optimisation model and a techno-economic model are applied to simulate the generation of electricity and hydrogen, as well as determine the most economical hydrogen supply scheme. Finally, a case study in the Beijing-Tianjin-Hebei region of China is taken to validate the benefits of the proposed roadmap. The preferred scheme is worked out with the net present value of 88.8 M$, including the economy configurations of the electricity-hydrogen hybrid generation system, as well as the hydrogen-natural gas blending plan. The results also indicate that annual electricity curtailment and annual carbon emission are decreased by 204 GWh (48.8%) and 40.2 kt (49.9%).

Solar thermal-activated photocatalysis for hydrogen production and aqueous triethanolamine polymerization

Solar thermal-activated photocatalysis (STAP) has been developed as an efficient sustainable technology for hydrogen generation and aqueous triethanolamine polymerization initiated by heterogeneous photocatalysts under solar light irradiation.

First-row transition metal-based materials derived from bimetallic metal–organic frameworks as highly efficient electrocatalysts for electrochemical water splitting

Electrochemical water splitting is a mature technology for hydrogen generation.

Biosynthesis of Ag–Pt bimetallic nanoparticles using propolis extract: Antibacterial effects and catalytic activity on NaBH4 hydrolysis

The critical environmental issues of antibiotic resistance and renewable energies supply urge researching materials synthesis and catalyst activity on hydrogen production processes. Aiming to analyse the antibacterial effect of platinum-silver (Ag–Pt) nanoparticles (NPs) and the catalyst effect on NaBH4 hydrolysis that can be used for hydrogen generation technology, in this work, Ag–Pt NPs were prepared using aqueous propolis extract. Various methods were used for the characterization (Uv–vis Spectroscopy, Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Atomic Force Microscopy (AFM) and X-ray diffraction Spectroscopy (XRD)). The antimicrobial activity of Ag–Pt bimetallic nanoparticles was evaluated in vitro by the microdilution method against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumoniae, Staphylococcus epidermidis, and Serratia marcescens. The results confirmed the antimicrobial activity of bimetallic NPs Ag–Pt concentrations of (25, 50, and 100 μg/ml). A concentration of 100 μg/ml showed low bacterial viability varying between 22.58% and 29.67% for the six tested bacteria. For the catalyst activity on NaBH4 hydrolysis, the results showed high turnover factor (TOF) and low activation energy of 1208.57 h−1 and 25.61 kJ/mol, respectively, with high hydrogen yield under low temperature. Synthesized Ag–Pt NPs can have great potential for biological and hydrogen storage applications.

Recent Advances in Complex Hollow Electrocatalysts for Water Splitting

AbstractElectrochemical water splitting powered by renewable energy sources has been considered as an attractive hydrogen generation technology with high‐purity product and zero carbon emission. However, the efficient realization of large‐scale water splitting is severely hampered by the sluggish hydrogen/oxygen evolution reaction (HER/OER). As an important class of functional materials, complex hollow electrocatalysts provide promising solutions to accelerate the HER/OER kinetics owing to their advantageous features, such as abundant exposed active sites, increased contact area between catalysts and electrolyte, and shortened mass/charge transport length. Herein, the recent advances in the development of complex hollow electrocatalysts and their outstanding performances in water splitting are summarized. Beginning with the introduction of reaction mechanisms and design principles, achievements in engineering complex hollow HER/OER electrocatalysts are highlighted with the focus on structural modulation, composition control, and electrocatalytic evaluation. Finally, some present challenges and future perspectives for advanced complex hollow electrocatalysts toward water splitting are further discussed.

Transition metal atoms M (M = Mn, Fe, Cu, Zn) doped nickel-cobalt sulfides on the Ni foam for efficient oxygen evolution reaction and urea oxidation reaction

Electrolysis of water is an environmentally friendly and promising hydrogen generation technology, which is one of the best ways to deal with the global energy crisis and environmental pollution. However, the slow anode reaction of water electrolysis is the bottleneck of limiting the efficient hydrogen production. Therefore, it is a key problem to explore an efficient and economical electrocatalyst to assist the anode reaction. Herein, a series of self-supporting M-NiCo2S4 /Ni3S2 (M=Mn, Fe, Cu, Zn) nanostructures grown on a nickel foam (NF) skeleton were prepared through one-step hydrothermal strategy. In this process, doping engineering is employed to adjust the electronic structure of catalyst and improve the performance of the catalyst. Among them, the introduction of Fe not only greatly changed the morphology, but also provided rich active sites. Specifically, the Fe-NiCo2S4/Ni3S2 electrode can achieve current densities of 50 and 100 mA cm−2 at overpotential of 159 and 210 mV in alkaline media for oxygen evolution reaction (OER). In addition, driving current densities of 50 and 100 mA cm−2 in 1.0 M KOH with 0.5 M urea only requires the ultra-small voltage of 1.37 and 1.39 V (vs. RHE) for urea oxidation reaction (UOR), indicating that UOR can well replace OER to reduce electrical energy consumption. The experimental results and density functional theory calculations (DFT) demonstrate that the superior activity of the catalyst can be attributed to the optimal water adsorption energy, faster electron transfer rate, more active site exposure and good electrical conductivity. This work extends the application of doping engineering in water electrolysis and provides a novel preparation method of efficient catalyst for OER and UOR.

Superhydrophilic porous transport layer enhances efficiency of polymer electrolyte membrane electrolyzers

A prominent technology for green hydrogen generation is the polymer electrolyte membrane (PEM) electrolyzer. However, the energy efficiency of PEM electrolyzers must improve dramatically to become economically competitive. Here, we engineer the wettability of commercial porous transport layers (PTLs) to make them superhydrophilic. We find that the superhydrophilic PTLs increase the efficiency of PEM electrolyzers by >11% at high current operation (up to 20%). We show via electrochemical analyses and in operando neutron imaging that the improved efficiency stems from reduced gas saturation in the anode PTL, which significantly decreases the mass transport overpotential. We conduct ex situ microfluidic experiments and demonstrate that capillary-driven corner flow is a key physical mechanism responsible for the reduced oxygen gas saturation and enhanced liquid water transport. Our findings illustrate the importance of PTL wettability on mass transport in PEM electrolyzers and enable the design of next-generation electrolyzers with much greater efficiency.

Recent Progress in Mixed-Matrix Membranes for Hydrogen Separation.

Membrane separation is a compelling technology for hydrogen separation. Among the different types of membranes used to date, the mixed-matrix membranes (MMMs) are one of the most widely used approaches for enhancing separation performances and surpassing the Robeson upper bound limits for polymeric membranes. In this review, we focus on the recent progress in MMMs for hydrogen separation. The discussion first starts with a background introduction of the current hydrogen generation technologies, followed by a comparison between the membrane technology and other hydrogen purification technologies. Thereafter, state-of-the-art MMMs, comprising emerging filler materials that include zeolites, metal-organic frameworks, covalent organic frameworks, and graphene-based materials, are highlighted. The binary filler strategy, which uses two filler materials to create synergistic enhancements in MMMs, is also described. A critical evaluation on the performances of the MMMs is then considered in context, before we conclude with our perspectives on how MMMs for hydrogen separation can advance moving forward.

Hydrogen Production by Fluidized Bed Reactors: A Quantitative Perspective Using the Supervised Machine Learning Approach

The current hydrogen generation technologies, especially biomass gasification using fluidized bed reactors (FBRs), were rigorously reviewed. There are involute operational parameters in a fluidized bed gasifier that determine the anticipated outcomes for hydrogen production purposes. However, limited reviews are present that link these parametric conditions with the corresponding performances based on experimental data collection. Using the constructed artificial neural networks (ANNs) as the supervised machine learning algorithm for data training, the operational parameters from 52 literature reports were utilized to perform both the qualitative and quantitative assessments of the performance, such as the hydrogen yield (HY), hydrogen content (HC) and carbon conversion efficiency (CCE). Seven types of operational parameters, including the steam-to-biomass ratio (SBR), equivalent ratio (ER), temperature, particle size of the feedstock, residence time, lower heating value (LHV) and carbon content (CC), were closely investigated. Six binary parameters have been identified to be statistically significant to the performance parameters (hydrogen yield (HY)), hydrogen content (HC) and carbon conversion efficiency (CCE) by analysis of variance (ANOVA). The optimal operational conditions derived from the machine leaning were recommended according to the needs of the outcomes. This review may provide helpful insights for researchers to comprehensively consider the operational conditions in order to achieve high hydrogen production using fluidized bed reactors during biomass gasification.

Enhanced hydrogen generation from hydrolysis of MgLi doped with expanded graphite

Hydrolysis of Mg-based materials is considered as a potential means of safe and convenient real-time control of H2 release, enabling efficient loading, discharge and utilization of hydrogen in portable electronic devices. At present work, the hydrogen generation properties of MgLi-graphite composites were evaluated for the first time. The MgLi-graphite composites with different doping amounts of expanded graphite (abbreviated as EG hereinafter) were synthesized through ball milling and the hydrogen behaviors of the composites were investigated in chloride solutions. Among the above doping systems, the 10 wt.% EG-doped MgLi exhibited the best hydrogen performance in MgCl2 solutions. In particular, the 22 h-milled MgLi-10 wt.% EG composites possessed both desirable hydrogen conversion and rapid reaction kinetics, delivering a hydrogen yield of 966 mL H2 g−1 within merely 2 min and a maximum hydrogen generation rate of 1147 mL H2 min−1 g−1, as opposed to the sluggish kinetics in the EG-free composites. Moreover, the EG-doped MgLi showed superior air-stable ability even under a 75 RH% ambient atmosphere. For example, the 22 h-milled MgLi-10 wt.% EG composites held a fuel conversion of 89% after air exposure for 72 h, rendering it an advantage for Mg-based materials to safely store and transfer in practical applications. The similar favorable hydrogen performance of MgLi-EG composites in (simulate) seawater may shed light on future development of hydrogen generation technologies.

Development of phase change materials using hydrolyzed Al-Bi composite powder for solar energy storage

The hydrogen generation technology using the hydrolysis of Al-based composite powders has recently gained an increasing attention. However, the emission of hydrogen generation waste residue stream is an urgent problem to be addressed in the actual manufacture. For this purpose, this study reported the development of phase change thermal energy storage materials using hydrogen generation waste residue stream from Al-based composite powder hydrolysis. Specifically, the rapid hydrolysis reaction of Al-Bi composite powders was used to generate hydrogen, and subsequently tetraethoxysilane of different masses was added to the hydrogen generation waste residue stream to prepare Al-Si/Al2O3 composite phase change materials (PCMs) with controllable melting temperature. The results indicated that the hydrogen generation yield of Al-Bi composite powders during the fabrication of composite PCMs was 537.3–565.7 mL/g. Importantly, the prepared composite PCMs, with a controllable melting temperature of 573.2–654.2 °C, thermal energy storage density of 30.9–37.3 J/g, great repeatable utilization performance and structural stability, were potential thermal energy storage materials for concentrated solar power plants. Thus, this study not only achieved the reuse of hydrogen generation waste residue stream but also offered a new method for preparing Al-based composite PCMs.

(Invited) High Efficiency PEM Water Electrolysis Enabled By Advanced Catalysts, Membranes and Processes

Commercial water electrolysis technologies, including proton exchange membrane electrolysis (PEMWE), are the only renewable hydrogen generation technologies that can achieve the U.S. Department of Energy (DOE) cost targets within the next ten years at the required scale, based on the supply chain maturity and materials performance. In particular, membrane and electrode modifications have enabled the use of advanced electrolysis membranes to achieve the efficiency targets, while nanoengineered alloy catalyst layers (CLs) have been pursued to meet the cost and efficiency targets. These advancements have been achieved by building the basic understanding to allow the successful technical development and include: (1) Mechanical and chemical understanding of membranes in liquid water below 90oC; (2) Characterization of as-deposited electrodes and MEAs after operation; (3) Water management in the anode catalyst layer, dependence on catalyst loading and porous transport layer form factor; and (4) Long-term degradation rate and stability of engineered alloy Ru-Ir alloy nanocatalysts in well-defined anode catalyst layers.Nel Hydrogen’s pathway to meet these DOE goals is through the i) use of 50-75% thinner membranes that operate at 80-90 oC, while controlling mechanical creep and gas crossover; ii) reducing the catalyst loading to 1/10th the current value on both electrodes, while controlling water distribution and the porous transport layer/catalyst layer (PTL/CL) electrochemical interface; iii) incorporation of a less stable but more active Ru containing catalyst managed on the anode side of the cell, which is achievable with lower voltage operation (accomplished via low ohmic drop in the anode catalyst layer, thinner membranes, and higher temperature operation); and iv) fabricating a membrane electrode assembly (MEA) integrating all of these characteristics.In this talk, some of the advancements achieved and how these have impacted the cost of hydrogen will be discussed, as well as the longer-term targets that need to be reached to provide the robustness required for commercial applications. Additionally, cost models will be compared along with sensitivity analysis to show how the impact of operating parameters, with regard to the capital and operational expense for the PEM electrolysis technology cost, show the critical areas to focus on to provide the largest impact towards meeting cost target goals and what is required to go beyond. Figure 1