Pure Hydrogen Production Research Articles

MOF-derived cobalt manganese phosphide as highly efficient electrocatalysts for hydrogen evolution reaction

Hydrogen is considered as a viable alternative to traditional fossil fuels. Hydrogen evolution reaction (HER) by electrochemical water splitting is the most reliable and effective way for the sustainable production of pure hydrogen. The design and synthesis of highly active and stable non-noble-metal-based electrocatalysts is the core of the large-scale application of this technology. Herein, peony petal-like CoMnP/NF nanomaterials growing on nickel foam (NF) are prepared via facile hydrothermal and phosphorization methods. The results showed that CoMnP/NF had excellent HER activity in acidic and alkaline media. In 0.5 M H2SO4, CoMnP/NF only needed 66.6 mV overpotential to drive the current density of 10 mA cm−2, with a Tafel slope of 38.8 mV dec−1. In addition, a particularly low overpotential of 53.9 mV and Tafel slope of 63 mV dec−1 are required to achieve the same current density in the 1 M KOH electrolyte. Meanwhile, the electrocatalyst showed good stability after 1000 cyclic voltammetry tests and 12 h I-T tests. In the 1 M KOH electrolyte, the current density of 10 mA cm−2 achieved with only 1.70 V battery voltage, and the electrocatalyst showed excellent stability. The performance of CoMnP/NF can be attributed to the synergistic effect between Co and Mn atoms and the high electrochemical surface area (ECSA). This study provides a valuable strategy for the synthesis of non-precious metals and high-performance catalytic materials.

Pure Hydrogen Production by Aqueous Ethanol Electrolysis on Pt–Ru–O Anodes in a Solid Polymer Electrolyte Electrolysis Cell

Pure Hydrogen Production by Aqueous Ethanol Electrolysis on Pt–Ru–O Anodes in a Solid Polymer Electrolyte Electrolysis Cell

Glycerol electro‐reforming in alkaline electrolysis cells for the simultaneous production of value‐added chemicals and pure hydrogen – Mini‐review

AbstractGlycerol is a cheap, non‐toxic, and renewable by‐product of the rapid expansion of biodiesel and soap producers around the world. Glycerol electroforming is a method of oxidizing glycerol into valuable chemicals of interest to the pharmaceutical, cosmetics, polymer, and food industries. One of the technologies that have been studied over the past decades is to couple glycerol oxidation with the production of pure hydrogen in an electrolysis cell (so‐called electrolyzer), which has shown the advantage of consuming a much lower theoretical amount of electricity than conventional water electrolysis. The efficiency of this device is influenced by the nature, structure, and composition of the electrode material. This mini‐review concerns the understanding of glycerol electro‐oxidation, a brief state of the art of nanomaterials currently used to prepare electrode materials, and some results concerning the performance of electrolyzers in alkaline conditions that combine the efficient production of value‐added chemicals and hydrogen.

Gas Crossover Regulation by Porosity-Controlled Glass Sheet Achieves Pure Hydrogen Production by Buffered Water Electrolysis at Neutral pH.

Near‐neutral pH water electrolysis driven by renewable electricity can reduce the costs of clean hydrogen generation, but its low efficiency and gas crossover in industrially relevant conditions remain a challenge. Here, it was shown that electrolyte engineering could suppress the crossover of dissolved gases such as O2 by regulating their diffusion flux. In addition, a hydrophilized mechanically stable glass sheet was found to block the permeation of gas bubbles, further enhancing the purity of evolved gas from water electrolysis. This sheet had a lower resistance than conventional diaphragms such as Zirfon due to its high porosity and small thickness. A saturated K‐phosphate solution at pH 7.2 was used as an electrolyte together with the hydrophilized glass sheet as a gas‐separator. This led to a near‐neutral pH water electrolysis with 100 mA cm−2 at a total cell voltage of 1.56 V with 99.9 % purity of produced H2.

Nano-LaCoO3 infiltrated BaZr0.8Y0.2O3− electrodes for steam splitting in protonic ceramic electrolysis cells

Protonic ceramic electrolysis cell (PCEC) is a promising technology for production of pure dry hydrogen due to the low operating temperature and high efficiency. One of the obstacles for commercialization of PCEC technology is the poor performance and insufficient long-term durability of the oxygen electrode. In this study, we address the above challenge by designing a LaCoO3 (LC) catalyst infiltrated porous BaZr0.8Y0.2O3−δ (BZY20) backbone electrode (LC-BZY20). The performance and durability of the LC-BZY20 electrode are investigated on symmetrical cells using electrochemical impedance spectroscopy (EIS). The total electrode polarization resistance (RP) values of the electrode are 0.56, 1.24, 2.18, and 2.90 Ω cm2 in 3 ​vol% humidified synthetic air at 600, 550, 500, and 450 ​°C, respectively, indicating good electrochemical performance of the LC-BZY20 electrode. Furthermore, the LC-BZY20 electrode displays good stability, without significant performance degradation when tested at 600 ​°C in 10 ​vol% humidified air for 900 ​h. We further study the influence of oxygen partial pressure (Po2) and steam partial pressure (PH2O) on the response of the EIS data, and propose a set of chemical and electrochemical processes involved in the steam splitting reaction in the LC-BZY20 electrode.

Pure hydrogen and sulfur production from H2S by an electrochemical approach using a NiCu–MoS2 catalyst

NiCu–MoS2 shows remarkable electrocatalytic activity towards H2S electrolysis and provides a promising route for easy sulfur recovery and energy saving H2 production compared to H2O electrolysis.

Effect of support preparation method on water-gas shift activity of copper-based catalysts

Reducing the effect of global warming and increasing the needs for fuel sources appoint hydrogen utilization in fuel cell technology a very promising demand. A step for required pure hydrogen production for this purpose is the water-gas shift (WGS) reaction and the design of well performing but cost effective WGS catalysts, the latter being of growing research interest. In the present study catalysts containing copper (3 wt%) supported on ceria/alumina (30 wt% ceria) and Y-doped ceria/alumina (1 wt% Y2O3 regarding ceria content) were prepared by impregnation (IM) and by mechanochemical mixing (MM). The effect of support synthesis methods on the performance in the WGS reaction was discussed based on catalyst characterization by means of XRD, HRTEM, XPS, and H2-TPR methods. It was established that the effect of Y-doping was strongly dependent on the method of support preparation being positive for MM and unfavourable in the case of impregnation. The IM method caused the formation of a superficial phase with CuO, Y-dopant, and ceria in close location. Additionally, a higher amount of oxygen vacancies was related to non-reducible Y3+ ions that interrupted Cu–oxygen vacancy–Ce interaction thus leading to both lower reducibility and WGS activity. The presence of yttria phase located on ceria-free alumina in the case of MM support decreased the negative influence of Ce3+ replacement by Y3+ ions. A positive effect of separate Y2O3 could explain the best WGS performance observed. Long-term WGS tests showed good stability thus making this catalyst promising composed mainly of alumina and low amount of active phases. The study contributes to the development of an advantageous formulation of well-performing and economically profitable WGS catalysts for efficient improving of hydrogen purity for small-scale applications.

Cyclic performance of coke oven gas - Steam reforming with assistance of steel slag derivates for high purity hydrogen production

Steel slag-derived CaO (CaO(SS)) was applied in cyclic sorption enhanced steam reforming of coke oven gas process (cyclic SE-SRCOG) for high-purity hydrogen production. Effects of leaching acid concentration on the cyclic CO2 capture capacity of CaO(SS) were investigated. Using 1 mol/L acetic acid solution as leaching solution, the prepared CaO-based sorbent showed a stable CO2 capture capacity of 0.27 gCO2/gCaO after 35 sorption-desorption cycles. Impacts of operating modes (with different particles contents and loading patterns), operating procedure, and leaching residue (LR) blending on cyclic SE-SRCOG performance were experimentally investigated in detail. Combined catalyst-sorbent by adhesively tableting exhibited the worst stability due to loss of Ni active sites, caused by severe sintering and coverage by CaCO3. With a reforming temperature of 600 °C, cyclic SE-SRCOG with layered packing catalyst-sorbent particles could achieve H2 purity of 95% and CH4 conversion of 87% at the 5th cycle, and they were still maintained to be 87% and 65% at the 10th cycle, respectively. In operating mode using layered packed catalyst-sorbent particles, integration of LR into the sorbent facilitated further improvements of CH4 conversion to 86% at the 10th cycle, mainly due to that LR could act as catalytic promoters of SRCOG and sintering-resistance spacers of CaO(SS).

Status and development of hydrogen preparation, storageand transportation

<p indent=0mm>As a kind of important clean and renewable energy, hydrogen energy has received increasing attention. In the past, the majority of researchers from colleges and universities, Chinese Academy of Sciences and other institutions carrying out hydrogen energy related research were supported by the National Natural Science Foundation of China, Ministry of Science and Technology. Nowadays many enterprises are also involved, including both private enterprises and state owned enterprises. This is a significant shift in this research field that will further promote the development of hydrogen energy industry. Hydrogen industry includes hydrogen production, separation, storage and transportation, application and other links. Great strides have been made in these fields in recent years. Some of these fields are developing rapidly, while others are still facing many challenges. This paper makes a systematic analysis and induction of the status, issues and future development potential of the hydrogen industry chain. The paper is divided into seven parts, including hydrogen preparation, hydrogen storage, hydrogen transportation, hydrogen pipeline transportation, liquid hydrogen manufacturing, storage and transportation, hydrogen refueling station, conclusions and suggestions. In the part of hydrogen preparation, we introduce the methods of hydrogen preparation, separation and purification, the annual changes of world pure hydrogen and mixed hydrogen production, the relationship between hydrogen price of different hydrogen production methods and main raw material price, and the comparison of hydrogen production technologies and characteristics of different electrolytic water. In the part of hydrogen storage, four main methods: High-pressure gas hydrogen storage, low-temperature liquid hydrogen storage, solid hydrogen storage and organic liquid hydrogen storage are introduced, and the performances of these four methods are compared. In the part of hydrogen transportation, we introduce several common hydrogen transportation methods, the performance comparison of several common hydrogen transportation methods, and the price variance by distance of the three main hydrogen transportation methods. In the part of hydrogen pipeline transportation, the construction of two domestic hydrogen pipelines and the comparison of relevant parameters, as well as the situation of hydrogen transportation pipelines around the world are introduced. In the part of liquid hydrogen production, storage and transportation, the production methods of liquid hydrogen, the difference in calorific value between hydrogen fuel and other fuels, the preparation level of liquid hydrogen all over the world and the development direction in the future are introduced. In the part of hydrogenation stations, the construction, operation, cost and problems of hydrogenation refueling stations around the world are introduced. Finally, based on the contents above, we draw some conclusions and suggestions as follows: (1) In terms of hydrogen production, it is necessary to reduce the cost, develop hydrogen production from fossil raw materials to clean energy electrolytic water, focus on the development of proton exchange membrane green hydrogen preparation technology and enlarge its scale. (2) In terms of hydrogen storage, it is necessary to select appropriate hydrogen storage methods and improve their performance according to different applications. In the field of transportation, it is necessary to develop a hydrogen storage system with a weight density greater than 5wt% and a volume density greater than <sc>40 g/L,</sc> which is cost-effective and easy to control hydrogen absorption and desorption. In the non-transportation field, it is necessary to develop large-scale, low energy consumption and high safety hydrogen storage technology. (3) In terms of hydrogen transportation, it is necessary to strengthen the development of pipeline hydrogen transportation and liquid hydrogen transportation technology. (4) In terms of hydrogen refueling station, it is necessary to realize the localization of key equipment such as compressors and hydrogen injectors, improve the operation efficiency of hydrogen refueling stations and reduce the operational cost; Hydrogen production stations and liquid hydrogen refueling stations need to be developed.

Experimental and simulation study of PEMFC based on ammonia decomposition gas as fuel

Compared with hydrogen, ammonia has the advantages of high gravimetric hydrogen densities (17.8 wt.%), ease of storage and transportation as a chemical hydrogen storage medium, while its application in small-scale on-site hydrogen production scenarios is limited by the need for complex separation equipment during high purity hydrogen production. Therefore, the study of PEMFC, which can directly utilize ammonia decomposition gas, can greatly expand the application of fuel cells. In this paper, the output characteristics, fuel efficiency and the variation trend of hydrogen concentration and local current density in the anode channel of fuel cell with the output voltage of PEMFC fueled by ammonia decomposition gas were studied by experiment and simulation. The results indicate that the maximum output power of the hybrid fuel decreases by 9.6% compared with that of the pure hydrogen fuel at the same inlet hydrogen equivalent. When the molar concentration of hydrogen in the anode channel is less than 0.12, the output characteristics of PEMFC will be seriously affected. Employing ammonia decomposition gas as fuel, the efficiency corresponding to the maximum output power of PEMFC is approximately 47%, which is 10% lower than the maximum efficiency of pure hydrogen.

Multi‐interfacial catalyst with spatially defined redox reactions for enhanced pure water photothermal hydrogen production

AbstractPhotocatalytic overall water splitting is a promising strategy to store abundant solar energy as clean fuel, but recombination of photogenerated carriers is the key factor that reduces the efficiency. Herein, we report multi‐interfacial ternary CoP@ZnIn2S4@Co3O4 photocatalyst with coordinated structural and electronic band coupling to concurrently fulfill spatially decoupled redox centers and modulated electric field. For one, the realization of 3D open framework consists of 2D ZnIn2S4 nanosheets on 1D CoP co‐catalyst maximizes exposures apart from circumvents aggregation and shielding issues. Another is the spatially defined and selective redox reactions where CoP is designated for proton reduction and Co3O4 for water oxidation. And finally, constructed type II band structure and p‐n junction facilitates directional charge separation, thereby prohibiting the recombination of charge carrier and also increase the local charge density. Besides, small band gap CoP and Co3O4 exhibit photothermal effect to further enhance photocatalytic hydrogen production. As a result, the photocatalysts could achieve the respective half reaction and pure water hydrogen evolution rate of 4254 and 145 μmol g−1 h−1 under visible light illumination and further enhance to 10 740 and 308 μmol g−1 h−1 when subjected to full spectrum photoheating. This work presents a promising strategy in designing surface and interfacial dominated photocatalytic system to achieve efficient solar energy to chemical conversion.image

Green hydrogen & electricity production via geothermal-driven multi-generation system: Thermodynamic modeling and optimization

Concerning limited sources of fossil fuels, humankind should ensue new avenues to meet its energy demands. Towards this, geothermal energy is acknowledged as a promising, reliable, safe, and clean means for this aim. In the present study, a multi-generation system driven by geothermal energy, which produces electrical power, hydrogen, oxygen, and cooling, is proposed, appraised from thermodynamic and economic standpoints. Due to today's importance of hydrogen production, pure hydrogen production is one of the primary purposes of the system here described and analyzed. The subsystems include an organic Rankine cycle (ORC), a polymer electrolyte membrane (PEM) electrolyzer, and a lithium/bromide absorption refrigeration cycle. The model is implemented in the Engineering Equation Solver software and a multi-objective optimization is performed with NSGA-II.The results indicate that the parameters mostly affecting system performance include geothermal fluid mass flow rate, geothermal fluid temperature, ORC turbines inlet temperature, and evaporator pinch-point. The highest exergy destruction is pertinent to evaporators and the PEM electrolyzer, respectively. Moreover, the results reveal that the higher the geothermal well temperature, the higher the output parameters of the system. Also, a case study was carried out to implement the proposed system in Sabalan geothermal wells; the results indicate that the system can support the energy need of 160 families during one year by producing 4,696 MWh of electrical power. Lastly, the multi-objective optimization lead to a optimal scenario with 37.85 % exergy efficiency and 15.09 USD/h system cost rate.

Large-scale decomposition of green ammonia for pure hydrogen production

It is acknowledged that Hydrogen has a decisive role to play in insuring a reliable and efficient penetration of renewable electricity in the energy mix. Nonetheless, building a sustainable Hydrogen Economy is faced with numerous challenges across the value chain. Namely, large-scale production and storage are still open issues that need to be addressed. A promising solution is to store renewable H2 in the form of green ammonia often referred to as Power-to-Ammonia. Thus unlocking all available infrastructure for ammonia to effectively store and export hydrogen in bulk. In this value chain, the missing link is ammonia cracking to recover back hydrogen at high purities. The present work explores a technical solution to recover hydrogen from ammonia at large-scale. Through an exhaustive technoeconomic analysis, we have demonstrated the feasibility of large-scale production of pure H2 from ammonia. The designed Ammonia-to-H2 plant operates at a thermal efficiency of 68.5% to produce 200 MTPD of pure hydrogen at 250 bar. Furthermore, this study has established a final estimation of the Levelized Cost of Hydrogen (LCOH) from green ammonia. It was revealed that LCOH is mostly dependent on green ammonia cost, which in turn varies with renewable electricity cost.

Techno-economic assessment of solar steam reforming of methane in a membrane reactor using molten salts as heat transfer fluid

This paper reports the results obtained in a techno-economic analysis of the Steam Methane Reforming (SMR) technology aided with solar heat, developed and demonstrated in the European FCH JU project CoMETHy: a compact membrane reformer heated with molten salt up to 550 °C allowed to simultaneously carry out methane steam reforming, water-gas-shift reaction and hydrogen separation. This reactor can be integrated with new generation Concentrating Solar Thermal (CST) systems to supply the process heat. Experimental validation of the technology has been successfully achieved in a pilot scale plant and the results recently published. In this paper, we introduce a fully-integrated scheme and operation strategies of a plant on the 1500 Nm3/h hydrogen production scale. Then, techno-economic analysis of this new solar-driven process is presented to evaluate its competitiveness. Considering a plant capacity of 1500 Nm3/h (pure hydrogen production) and today's costs for the methane feed and the CST technology, obtained Hydrogen Production Cost (HPC) are in the range of 2.8–3.3 €/kg for a “solar-hybrid” system with high capacity factor (8000 h/year operation) and 4.7 €/kg for a “solar-only” case, while HPC≅1.7 €/kg can be obtained with the conventional route under equivalent assumptions. However, a sensitivity analysis shows that the expected drop of the cost of the CST technology will bring the HPC around 2.4 €/kg for the “solar-hybrid” case and close to 3.4 €/kg for the “solar-only” case, thus making the cost of solar reforming closer to conventional SMR with CO2 capture and with wind/solar electrolysis in the future. In the “solar-hybrid” case total CO2 production can be reduced by 13–29% with 58–70% of produced CO2 recovered as pure stream (at 1.3 bar); in the “solar-only” case total CO2 production can be reduced by 52% and 100% of produced CO2 recovered as pure stream (at 1.3 bar). However, compared to the conventional route, CO2 avoidance costs are still relatively high (≥137 €/tonCO2) and process optimization measures required. Therefore, optimization measures have been outlined to increase the overall process efficiency and further reduce the HPC.

Design and development of defect rich titania nanostructure for efficient electrocatalyst for hydrogen evolution reaction in an acidic electrolyte

Cost-effective, efficient and stable electrocatalyst for water splitting in the acidic electrolyte medium has been developed. The acidic electrolyte could be a support for the high purity hydrogen production via water splitting. Accordingly, we have prepared the defect-rich titania nanostructure via electrochemical anodization and cathodization routes using the titanium plate, which showed highly effective and durable electrocatalyst of hydrogen evolution reaction (HER) in an acidic medium. This hybrid compound showed a low onset potential of −0.17 V for HER with a current density of −150 mA cm−2 in 1 M H2SO4. Moreover, the stability test has been performed with the defect-rich titania nanostructure as cathode for 6 h in the two electrodes system.

Integrating Hydrogen Production and Transfer Hydrogenation with Selenite Promoted Electrooxidation of α-Nitrotoluenes to E-Nitroethenes.

Developing an electrochemical carbon-added reaction with accelerated kinetics to replace the low-value and sluggish oxygen evolution reaction (OER) is markedly significant to pure hydrogen production. Regulating the critical steps to precisely design electrode materials to selectively synthesize targeted compounds is highly desirable. Here, inspired by the surfaced adsorbed SeOx 2- promoting OER, NiSe is demonstrated to be an efficient anode enabling α-nitrotoluene electrooxidation to E-nitroethene with up to 99 % E selectivity, 89 % Faradaic efficiency, and the reaction rate of 0.25 mmol cm-2 h-1 via inhibiting side reactions for energy-saving hydrogen generation. The high performance can be associated with its in situ formed NiOOH surface layer and absorbed SeOx 2- via Se leaching-oxidation during electrooxidation, and the preferential adsorption of two -NO2 groups of intermediate on NiOOH. A self-coupling of α-carbon radicals and subsequent elimination of a nitrite molecule pathway is proposed. Wide substrate scope, scale-up synthesis of E-nitroethene, and paired productions of E-nitroethene and hydrogen or N-protected aminoarenes over a bifunctional NiSe electrode highlight the promising potential. Gold also displays a similar promoting effect for α-nitrotoluene transformation like SeOx 2- , rationalizing the strategy of designing materials to suppress side reactions.

Integrating Hydrogen Production and Transfer Hydrogenation with Selenite Promoted Electrooxidation of α‐Nitrotoluenes to E‐Nitroethenes

AbstractDeveloping an electrochemical carbon‐added reaction with accelerated kinetics to replace the low‐value and sluggish oxygen evolution reaction (OER) is markedly significant to pure hydrogen production. Regulating the critical steps to precisely design electrode materials to selectively synthesize targeted compounds is highly desirable. Here, inspired by the surfaced adsorbed SeOx2− promoting OER, NiSe is demonstrated to be an efficient anode enabling α‐nitrotoluene electrooxidation to E‐nitroethene with up to 99 % E selectivity, 89 % Faradaic efficiency, and the reaction rate of 0.25 mmol cm−2 h−1 via inhibiting side reactions for energy‐saving hydrogen generation. The high performance can be associated with its in situ formed NiOOH surface layer and absorbed SeOx2− via Se leaching‐oxidation during electrooxidation, and the preferential adsorption of two ‐NO2 groups of intermediate on NiOOH. A self‐coupling of α‐carbon radicals and subsequent elimination of a nitrite molecule pathway is proposed. Wide substrate scope, scale‐up synthesis of E‐nitroethene, and paired productions of E‐nitroethene and hydrogen or N‐protected aminoarenes over a bifunctional NiSe electrode highlight the promising potential. Gold also displays a similar promoting effect for α‐nitrotoluene transformation like SeOx2−, rationalizing the strategy of designing materials to suppress side reactions.

Metal Supported Proton Conducting Ceramic Cell with Thin Film Electrolyte for Electrolysis Application

Solid oxide fuel cells and electrolysis cells (SOC) have been comprehensively developed as energy conversion and storage devices in recent years. Compared with oxygen ion conducting SOC, proton-conducting ceramic (PCC) cells are more suitable for the operation in the temperature range of 450~650 oC. The reduced operating temperature makes it especially attractive for steam electrolysis application aiming at valorizing waste heat from industrial processes. Moreover, during electrolysis in PCC cells, by design, the water-splitting reaction occurs at the oxygen electrode which enables the production of pure hydrogen at the fuel electrode.Based on previous research on metal-supported solid oxide cells (MS-SOC)[1] at DLR, MS-PCC with thin film electrolyte were investigated in this present study. The low temperature fabrication route (< 1000 °C) was chosen to avoid the serious corrosion of metal substrate at high temperature (1300~1400 °C) which is necessary for making the dense BaZrO3 based electrolyte in traditional sintering routes. In this case, pulsed laser deposition has been used for preparing the 1~2 µm thick electrolyte. Porous ferritic stainless steel, which has been used as the substrate, was cut into a round shape of 18 mm in diameter. To mitigate the Cr diffusion from metal substrate and formation of impurity phase between the metal substrate and NiO/BaZrxCe0.9-xY0.1O3-δ (NiO-BZCY) anode functional layer during processing or operation, Sr-doped LaMnO3 (LSM) was employed as the barrier layer in between. Both LSM and NiO-BZCY layers were processed by lamination of tape-cast thin films onto the metal substrate respectively and successfully co-sintered below 1000 °C. The thermomechanical stability of the thin film electrolyte was investigated by simulating thermal cycles from room temperature up to 950 °C. Platinum and Ba1-xGd0.8La0.2+xCo2O6- δ [2] were considered as oxygen electrode materials. Electrochemical characterization was carried out in both fuel cell and electrolysis operations. Advantages and current limitations of the presented cell design are discussed.Part of this work was supported by the project DAICHI funded by EIG CONCERT-Japan. The German part was funded by the Federal Ministry of Education and Research (project 01DR18002), the Norwegian part funded by the Research Council of Norway (project 284289). The China Scholarship Council is acknowledged for the doctoral scholarship of Haoyu Zheng (201806160173).Figure.1 Scanning electron microscopy (SEM) image of the metal supported proton conducting cells.[1] Costa R., Han F., Szabo P., et al. Fuel Cells, 2018, 18 (3): 251-259.[2] Vøllestad E., Strandbakke R., Tarach M., et al. Nature Materials, Jul, 2019, 18 (7): 752-759. Figure 1

Robust multi-objective optimization of methanol steam reforming for boosting hydrogen production

Methanol steam reforming (MSR) has been considered as a promising method for producing pure hydrogen in recent decades. A comprehensive two-dimensional steady-state mathematical model was developed to analyze the MSR reactor. To improving high purity hydrogen production, a triple-objective optimization of the MSR reactor is performed. Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is employed as a robust optimization approach to maximize the three objectives, termed as, methanol conversion, CO selectivity, and H2 selectivity. The Pareto optimal frontier has also been provided and the ultimate solution of the Pareto front has been found by the three decision-making methods (TOPSIS, LINMAP, and Shannon's Entropy). Among the three distinct decision-making approaches, LINMAP presents better results according to the deviation index parameter. It has been shown that a perfect agreement is available between the plant and simulation data. Operating under the optimum values based on the LINMAP method confirms an almost 47.04% enhancement of H2 mass fraction compared to the conventional industrial MSR reactor. The predicted results advocate that the key superiority of the optimized-industrial reactor is the remarkable higher production rate of hydrogen compared to the conventional MSR reactor which makes optimized-industrial reactor both feasible and beneficial.

Multifunctional Ni-based oxygen carrier for H2 production by sorption enhanced chemical looping reforming of ethanol

The sorption enhanced chemical looping reforming is a prospective technology for high-quality hydrogen production. In this technology, the full benefits of catalysis, oxygen transfer, and CO2 adsorption are achieved by the utilization of oxygen carriers and sorbents. However, most sorbents that are mixed physically into the reforming bed are liable to encountering ash fouling and porosity reduction, preventing CO2 adsorption and sorbent regeneration. In this work, we develop a multifunctional composite oxygen carrier, which combines the NiO/NiAl2O4 catalyst with the CaO sorbent into a one-body composite pellet. Compared with the conventional physically mixed oxygen carrier, the composite oxygen carrier shows uniform element distribution, superior reducibility, and shortened dead time, resulting in enhanced CO2 adsorption capacity, high H2 production efficiency, and excellent ethanol conversion. Furthermore, during 20 cycle tests, the stable CO2 adsorption capacity and H2 concentration of composite oxygen carrier were maintained, while the H2 concentration of mixed oxygen carrier sharply decreased because of deteriorated adsorption performance. The results confirm that the multifunctional composite oxygen carrier is more suitable than the mixed oxygen carrier for CO2 adsorption and high purity hydrogen production. This work opens a new avenue toward the performance improvement of oxygen carriers.