Industrial Hydrogen Production Research Articles

Electrified methane reforming: A compact approach to greener industrial hydrogen production

Electrification of conventionally fired chemical reactors has the potential to reduce CO2 emissions and provide flexible and compact heat generation. Here, we describe a disruptive approach to a fundamental process by integrating an electrically heated catalytic structure directly into a steam-methane-reforming (SMR) reactor for hydrogen production. Intimate contact between the electric heat source and the reaction site drives the reaction close to thermal equilibrium, increases catalyst utilization, and limits unwanted byproduct formation. The integrated design with small characteristic length scales allows compact reactor designs, potentially 100 times smaller than current reformer platforms. Electrification of SMR offers a strong platform for new reactor design, scale, and implementation opportunities. Implemented on a global scale, this could correspond to a reduction of nearly 1% of all CO2 emissions.

Amorphous CoFe Double Hydroxides Decorated with N-Doped CNTs for Efficient Electrochemical Oxygen Evolution.

The development and design of a highly active and affordable nanostructured material as an efficient electrocatalyst for electrochemical oxygen evolution is a pressing necessity to realize industrial production of hydrogen by water electrolysis. Amorphous nanocomposites have recently attracted interest owing to their superior electrocatalytic activity derived from their unique structure. Herein, amorphous CoFe double hydroxides (Am-CFDH) decorated with N-doped carbon nanotubes (NCNTs) is synthesized by a facile and simple one-pot approach under room temperature. Through electrochemical measurement, the bare Am-CFDH nanocomposite already exhibits a comparable oxygen evolution reaction (OER) activity to the commercial IrO2 catalyst on account of its amorphous nature and the interaction between Co and Fe. The introduced NCNTs can provide better electrical conductivity, more anchoring sites, and functional groups for enhancing the transfer of electrons and reactants, preventing the agglomeration of Am-CFDH to expose more active sites, and improving the synergistic effect between Am-CFDH and NCNTs. Thus, the Am-CFDH/NCNTs hybrid displays favorable durability beyond 20 h and advanced OER activity, owning a small overpotential of 270 mV at 10 mA cm-2 and a low Tafel slope of 56.88 mV dec-1 in alkaline medium.

Hydrogen production system with fuzzy logic-controlled converter

Electrolyte current must be controlled in the water electrolysis systems. For this purpose, the power converter for the cell stack of the electrolyzer used in industrial hydrogen production is realized. A series resonant converter, which is suitable for high input voltage and low output current applications, is used as power stage of the electrolyzer. The high-frequency transformer is used for the impedance matching. While the system is running, the electrical resistance of the electrolyzer changes continuously; thus, fuzzy logic controller (FLC) is used to control the output current of the power converter. In this study, a 700-W converter prototype is designed and controlled by the frequency modulation technique in the range of 290--360 kHz. The converter is tested for different output currents and it is observed that the power switches are turned on under soft switching conditions while FLC closely follows reference inputs.

Electro-catalytic steam reforming of methane over Ni-CeO2/γ-Al2O3-MgO catalyst

Catalytic steam reforming of methane with Ni-based catalysts is essential for industrial hydrogen production, but the high reforming temperature results in the catalyst deactivation by severe carbon deposition. In this work, a novel electro-catalytic protocol for steam reforming of methane was developed with aims of lowering the reforming temperature and prolonging the catalyst life. Three Ni-based catalysts, i.e., Ni/γ-Al2O3 (Ni/Al2O3), Ni/γ-Al2O3-MgO (Ni/AM) and Ni-CeO2/γ-Al2O3-MgO (Ni-CeO2/AM) were prepared for electro-catalysis to investigate the effects of current intensity, reforming temperature, and steam to carbon ratio on methane conversion, H2 yield and CO selectivity. Moreover, stability tests were performed on the three catalysts. The results indicated that the presence of electric current promoted the methane steam reforming at relatively low temperatures. Among the three catalysts, Ni-CeO2/AM showed the best performance on catalytic efficiency. Under conditions of 600 °C and current of 4.5A, CH4 conversion, H2 yield and CO selectivity achieved 96.4%, 75.3% and 40.1% respectively over Ni-CeO2/AM, which were comparable with those from conventional process at 700 °C. Moreover, after a 9-hour stability test, the CH4 conversion was maintained over 95% under Ni-CeO2/AM. Characterization results of the catalysts from the stability texts showed that the current could help generate more active centers for CH4 activation while inhibit the conversion of coke precursors into carbon on the catalyst surface.

Room-temperature electrochemical water\u2013gas shift reaction for high purity hydrogen production

Traditional water–gas shift reaction provides one primary route for industrial production of clean-energy hydrogen. However, this process operates at high temperatures and pressures, and requires additional separation of H2 from products containing CO2, CH4 and residual CO. Herein, we report a room-temperature electrochemical water–gas shift process for direct production of high purity hydrogen (over 99.99%) with a faradaic efficiency of approximately 100%. Through rational design of anode structure to facilitate CO diffusion and PtCu catalyst to optimize CO adsorption, the anodic onset potential is lowered to almost 0 volts versus the reversible hydrogen electrode at room temperature and atmospheric pressure. The optimized PtCu catalyst achieves a current density of 70.0 mA cm−2 at 0.6 volts which is over 12 times that of commercial Pt/C (40 wt.%) catalyst, and remains stable for even more than 475 h. This study opens a new and promising route of producing high purity hydrogen.

Numerical studies on heat coupling and configuration optimization in an industrial hydrogen production reformer

Steam methane reforming furnaces are the most important devices in the hydrogen production industry. The highly endothermic reaction system requires reaction tubes in the furnace to have a large heat transfer area and to be operated under high temperature and pressure conditions. In order to enhance heat transfer efficiency and protect reaction tubes, the controlling and optimization of the furnace structure have increasingly received more and more research attention. As known from the furnace structure, it is essential to couple the exothermic combustion with the endothermic reforming reactions due to the highly interactive nature of the two processes. Thus, in this paper, the combustion process in the furnace was numerically studied by using computational fluid dynamics (CFD) to model the combustion chamber, coupled with methane steam reforming reaction inside the reaction tubes, defined by a plug flow model. A set of combustion models were compared for the furnace chamber and a plug flow reaction model was employed for reforming reaction tubes, and then a heat coupling process was established. The predicted flue gas temperature distribution showed that the heat transfer in the furnace was not uniform, resulting in hot spots and heat losses on the tube wall. Therefore, structure optimization schemes were proposed. Optimization on arrangements of the tubes and the nozzles promoted the uniform distribution of flue-gas temperature and then improved heat transfer efficiency, thereby enhancing performance of the steam reforming process.

Theoretical investigation of platinum-like catalysts of molybdenum carbides for hydrogen evolution reaction

Developing high-active, stable and low-cost hydrogen evolution reaction (HER) catalysts is essential for industrial hydrogen production. Herein, a systematic study of the structures of molybdenum carbides and the related HER mechanism have been carried out based on density functional theory (DFT) calculations. The electronic properties and surface energies of three typical crystals of molybdenum carbides, i.e., α-MoC, β-MoC and γ-Mo2C, have been analyzed. It is shown that all the systems considered exhibit metallic behavior, among which the β-MoC (110) plane is the most active facet with the largest surface energy (3.159 J·m−2). By comparing the Gibbs free energies, ΔG(H), we find that the (111) surface of β-MoC has the smallest ΔG(H) of 0.089 eV, which is even superior than Pt-like catalysts, V8C7 (-0.114 eV), VC (−0.191 eV) or MoO2 (0.15 eV).

Numerical Investigation of the Effects of Steam Mole Fraction and the Inlet Velocity of Reforming Reactants on an Industrial-Scale Steam Methane Reformer

Steam methane reforming (SMR) is the most common commercial method of industrial hydrogen production. Control of the catalyst tube temperature is a fundamental demand of the reformer design because the tube temperature must be maintained within a range that the catalysts have high activity and the tube has minor damage. In this paper, the transport and chemical reaction in an industrial-scale steam methane reformer are simulated using computational fluid dynamics (CFD). Two factors influencing the reformer temperature, hydrogen yield and stress distribution are discussed: (1) the mole fraction of steam (YH2O) and (2) the inlet velocity of the reforming reactants. The purpose of this paper is to get a better understanding of the flow and thermal development in a reformer and thus, to make it possible to improve the performance and lifetime of a steam reformer. It is found that the lowest temperature at the reforming tube surface occurs when YH2O is 0.5. Hydrogen yield has the highest value when YH2O is 0.5. The wall shear stress at the reforming tube surface is higher at a higher YH2O. The surface temperature of a reforming tube increases with the inlet velocity of the reforming reactants. Finally, the wall shear stress at the reforming tube surface increases with the inlet velocity of the reforming reactants.

An Efficient, Visible‐Light‐Driven, Hydrogen Evolution Catalyst NiS/ZnxCd1−xS Nanocrystal Derived from a Metal–Organic Framework

AbstractPhotocatalytic water splitting for hydrogen production using sustainable sunlight is a promising alternative to industrial hydrogen production. However, the scarcity of highly active, recyclable, inexpensive photocatalysts impedes the development of photocatalytic hydrogen evolution reaction (HER) schemes. Herein, a metal–organic framework (MOF)‐template strategy was developed to prepare non‐noble metal co‐catalyst/solid solution heterojunction NiS/ZnxCd1−xS with superior photocatalytic HER activity. By adjusting the doping metal concentration in MOFs, the chemical compositions and band gaps of the heterojunctions can be fine‐tuned, and the light absorption capacity and photocatalytic activity were further optimized. NiS/Zn0.5Cd0.5S exhibits an optimal HER rate of 16.78 mmol g−1 h−1 and high stability and recyclability under visible‐light irradiation (λ>420 nm). Detailed characterizations and in‐depth DFT calculations reveal the relationship between the heterojunction and photocatalytic activity and confirm the importance of NiS in accelerating the water dissociation kinetics, which is a crucial factor for photocatalytic HER.

An Efficient, Visible‐Light‐Driven, Hydrogen Evolution Catalyst NiS/ZnxCd1−xS Nanocrystal Derived from a Metal–Organic Framework

Photocatalytic water splitting for hydrogen production using sustainable sunlight is a promising alternative to industrial hydrogen production. However, the scarcity of highly active, recyclable, inexpensive photocatalysts impedes the development of photocatalytic hydrogen evolution reaction (HER) schemes. Herein, a metal-organic framework (MOF)-template strategy was developed to prepare non-noble metal co-catalyst/solid solution heterojunction NiS/Znx Cd1-x S with superior photocatalytic HER activity. By adjusting the doping metal concentration in MOFs, the chemical compositions and band gaps of the heterojunctions can be fine-tuned, and the light absorption capacity and photocatalytic activity were further optimized. NiS/Zn0.5 Cd0.5 S exhibits an optimal HER rate of 16.78 mmol g-1 h-1 and high stability and recyclability under visible-light irradiation (λ>420 nm). Detailed characterizations and in-depth DFT calculations reveal the relationship between the heterojunction and photocatalytic activity and confirm the importance of NiS in accelerating the water dissociation kinetics, which is a crucial factor for photocatalytic HER.

MnMoO4 nanosheet array: an efficient electrocatalyst for hydrogen evolution reaction with enhanced activity over a wide pH range

We report the preparation of MnMoO4 nanosheet array on nickel foam (MnMoO4 NSA/NF) as an excellent 3D hydrogen evolution reaction (HER) electrocatalyst with good catalytic performance applied under basic, acidic and neutral conditions. In 0.5 M H2SO4, this MnMoO4 NSA/NF electrode needs an overpotential of 89 mV to drive current densities of 10 mA cm−2, to achieve the same current density, it demands overpotentials of 105 mV in 1.0 M KOH, 161 mV in 1.0 M PBS (pH = 7), respectively. After continuous CV scanning for 1000 cycles under different pH conditions, it also demonstrates an excellent stability with ignorable activity decrease. Such preeminent HER performance may be derived from the synergistic effect between manganese (Mn) and molybdenum (Mo) atoms, exposure of more active sites on the nanosheets and effective electron transport along the nanosheets. This MnMoO4 NSA/NF electrocatalyst provides us a highly efficient material for water splitting devices for industrial hydrogen production.

Mo- and Fe-Modified Ni(OH)2/NiOOH Nanosheets as Highly Active and Stable Electrocatalysts for Oxygen Evolution Reaction

Highly active and stable electrocatalysts for oxygen evolution reaction (OER) are required for industrial hydrogen production. Herein, we report Mo and Fe modification as a synergistic effect to enhance both activity and stability for OER. The Mo- and Fe-modified Ni(OH)2/NiOOH nanosheets needs an overpotential of only ∼280 mV to achieve a current density of 100 mA cm–2 and shows no evidence of degradation after 50 h at such high current density, outperforming all OER catalysts reported to date. This work may provide options for the design and preparation of promising OER electrocatalysts.

Closed-loop identification for plants under model predictive control

Model predictive controllers incorporate step response models for pairings of independent and dependent variables. Motivated by the fact that it may be time-consuming to conduct open-loop experiments to identify the step response models, the paper assesses the performance of closed-loop system identification on MPC-equipped plants, using both simulated and actual plant data. Pure feedback closed-loop system identification is shown to be effective for an identifiable simulated system and an industrial hydrogen production plant. The use of closed-loop system identification as a mechanism for monitoring model quality in MPC implementations may enhance the long-term sustainability of the implementation.

Field-Driven Splitting of Pure Water Based on Deep-Sub-Debye-Length Nanogap Cells

Hydrogen is a clean and renewable energy resource. Today, more than 90% of the industrially-produced hydrogen comes from steam reforming of natural gas, which are non-renewable and generate greenhouse gases as by-products. Water electrolysis can be a solution for a sustainable energy supply. However, only 4% of the industrial hydrogen production comes from water electrolysis, basically due to the low conversion efficiency. In this paper, we have demonstrated a novel method to achieve efficient pure water splitting based on our deep-sub-Debye-length nanogap cells, with efficiency that can be even better than 1 mol/L NaOH solution. This is the first time that even pure water can be efficiently electrolyzed. For traditional water electrolysis in macro-system, electric field has been screened into double layer region due to high-concentration electrolyte added to increase water conductivity. The weak electric field inside bulk solution leads to slow ion transport and thus slow reaction rate. In our nanogap cells with pure water, double layer regions of cathode and anode are overlapped so that huge electric field can exist in the entire electrode gap. When the gap is small enough (Figure 1), the migration rate can be even larger than electron-transfer rate (a.k.a. chemical reaction), leading to much higher efficiency than traditional method. The high electric field enhances water ionization and ion transport. From a microscopic perspective, the conductivity of water has been enhanced “equivalently”. We have named this process “virtual breakdown mechanism”. Figure 2 shows the schematic diagram and fabrication result of our metal-dielectric-metal sandwiched-like nanogap cells, achieved by common photolithography and low DC-bias nitride etching. The gap distance (or nitride thickness) has been down to 37 nm. I-V curve measurements based on our nanogap cells with pure DI water are shown in Figure 3. When gap distance shrank, the electrolysis current became larger due to higher electric field between two electrodes (Figure 3(a)). The threshold voltage around 1.5 V suggests that the energy efficiency is very close to 100% based on a thermoneutral potential of 1.48 V. Figure 3(b) shows currents saturated at fixed voltages when the gap distance became smaller, indicating electron-transfer limited reactions. The electrolysis of pure water and 1 mol/L NaOH solution were compared in Figure 4, both based on our nanogap cells. The different data dispersion indicates the different reaction locations for pure water and NaOH solution (Figure 4(b)). The electrolysis current from pure water was comparable to that from 1 mol/L sodium hydroxide solution, indicates more than 105-fold enhancement of equivalent conductivity of pure water. Figure 1

Nickel nanoparticles partially embedded into carbon fiber cloth via metal-mediated pitting process as flexible and efficient electrodes for hydrogen evolution reactions

Sunlight-driven electrolytic splitting of water is a promising route to hydrogen production, and widespread implementation has called for the development of inexpensive, robust and large-scale electrodes. Here, nickel nanoparticles partially embedded into carbon fiber cloth (NiΦCFC) is prepared on a large scale (e.g., 40 cm × 40 cm) via a metal-mediated pitting process, which is adopted to fabricate hydrogen evolution reaction electrode for the first time. The partially embedded structure is beneficial for regulating the electron density state of carbon, exposing the nickel catalytic sites and improving the catalytic stability. The two kinds of electrochemical area and density functional theory results confirm that the interface effect between nickel and defective carbon leads into a low Gibbs free energy of H* adsorption. The NiΦCFC as flexible and efficient electrodes require a small overpotential of 131.5 mV to achieve −10 mA cm−2. Note that the two-electrode electrolyzer composed of FeNi layered double hydroxide loaded on CFC (NiFe-LDH/CFC) (+)//NiΦCFC (−) possesses a voltage of 1.54 V at −10 mA cm−2, which can also be powered by a solar cell. The facile and large-scale preparation of NiΦCFC as flexible electrodes could be adapted for the industrial hydrogen production powered by solar energy.

Site-Dependent Environmental Impacts of Industrial Hydrogen Production by Alkaline Water Electrolysis

Industrial hydrogen production via alkaline water electrolysis (AEL) is a mature hydrogen production method. One argument in favor of AEL when supplied with renewable energy is its environmental superiority against conventional fossil-based hydrogen production. However, today electricity from the national grid is widely utilized for industrial applications of AEL. Also, the ban on asbestos membranes led to a change in performance patterns, making a detailed assessment necessary. This study presents a comparative Life Cycle Assessment (LCA) using the GaBi software (version 6.115, thinkstep, Leinfelden-Echterdingen, Germany), revealing inventory data and environmental impacts for industrial hydrogen production by latest AELs (6 MW, Zirfon membranes) in three different countries (Austria, Germany and Spain) with corresponding grid mixes. The results confirm the dependence of most environmental effects from the operation phase and specifically the site-dependent electricity mix. Construction of system components and the replacement of cell stacks make a minor contribution. At present, considering the three countries, AEL can be operated in the most environmentally friendly fashion in Austria. Concerning the construction of AEL plants the materials nickel and polytetrafluoroethylene in particular, used for cell manufacturing, revealed significant contributions to the environmental burden.

Techno‐Economic Analysis of Methane Pyrolysis in Molten Metals: Decarbonizing Natural Gas

AbstractMethane pyrolysis using a molten metal process to produce hydrogen is compared to steam methane reforming (SMR) for the industrial production of hydrogen. Capital and operating cost models for pyrolysis and SMR were used to generate cash‐flow and production costs for several different molten pyrolysis systems. The economics were most sensitive to the methane conversion and the value obtained for the solid carbon by‐product. The pyrolysis system at 1500 °C is competitive with a carbon tax of $78 t−1; however, if a catalytic process at 1000 °C were developed using a conventional fired heater, it would be competitive with SMR without a carbon dioxide cost penalty. Several pyrolysis alternatives become competitive with increasing carbon dioxide taxes.

Pt/Fe-NF electrode with high double-layer capacitance for efficient hydrogen evolution reaction in alkaline media

The electrode with high catalytic activity, low hydrogen overpotential and low cost is desired for hydrogen evolution reaction (HER) via electrocatalytic water splitting. In this study, Pt/Fe-Ni foam (Pt/Fe-NF) electrode was synthesized via cathodic electrodeposition followed by impregnation deposition. Physical and electrochemical properties of Pt/Fe-NF, NF and Pt/NF electrodes were characterized by various techniques. The Pt/Fe-NF electrode exhibited better electrochemical activity for HER under alkaline condition than those of Pt/NF and NF electrodes, owing to the introduction of zero valences Pt and Fe onto the NF, and synergetic effect resulted from the formation of Fe-Ni alloy. Furthermore, Pt/Fe-NF electrode showed extremely high double-layer capacitance (69.1 mFcm−2), suggesting high active sites for the Pt/Fe-NF. Tafel slope of Pt/Fe-NF was 59.9 mV dec−1, indicating that the Volmer-Heyrovsky HER mechanism was the rate-limiting step. The Pt/Fe-NF electrode with great electrocatalytic activity is a promising electro-catalyst for industrial hydrogen production from alkaline electrolyte.

A physics-based model for industrial steam-methane reformer optimization with non-uniform temperature field

In an industrial hydrogen production facility, steam-methane reforming reactions take place inside hundreds of catalyst-filled tubes placed in a large scale, high temperature furnace. Process efficiency depends strongly on the wall temperature distribution of the ensemble of reformer tubes; a narrower distribution has a process intensification effect, by providing similar processing experience to every feedstock molecule. Such process intensification efforts require a furnace model that can predict the temperature distribution as a function of operating conditions. Currently available furnace modeling solutions are either computationally intensive, making them unsuitable for (online) optimization calculations, or empirical, having limited accuracy when wide changes in operating conditions are required. In this work, a physics-based furnace model is presented that overcomes these limitations. Empirical perturbations in a Hottel zone radiation model are proposed to capture the spatially non-symmetrical temperature distribution. The low computational time makes the model suitable for operational intensification based on reduction of temperature distribution non-uniformity.

Hydrogen production: Perspectives, separation with special emphasis on kinetics of WGS reaction: A state-of-the-art review

Fossil fuel depletion, global warming, energy security, and climate change spur interest in commercial and environmentally friendly alternative fuels. Palladium-based catalytic membrane technology currently produces ultrapure hydrogen from fossil fuels. Palladium exhibits high permeability, selectivity for hydrogen, and good surface properties. Properties of some palladium alloys enable the industrial production of hydrogen. Reaction rates and conversion depend on several parameters. This document reviews kinetic expressions for the water–gas shift (WGS) reactions and WGS combined with Fischer–Tropsch synthesis (WGS–FTS) reactions at high and low temperatures along with the details of the catalysts and operating conditions. The discussion includes mathematical reactor modeling.