Hydrogen Production In Reactor Research Articles

Thermodynamic and economic analysis of a novel thermoelectric-hydrogen co-generation system combining compressed air energy storage and chemical energy

With the adjustment of energy structure, the proportion of renewable energy is gradually increasing, and how to solve the problem of renewable energy consumption is becoming more and more prominent. Therefore, a novel thermoelectric-hydrogen co-generation system combining compressed air energy storage (CAES) and chemical energy (CE) is proposed. For energy storage, the system uses adiabatic compression with liquid piston to reduce the generation of compression heat, while using the generated compression heat to preheat the methanol. For energy release, the methanol is fed into the methanol steam reforming reactor (MSR) and the methanol decomposition reactor (MDR) in certain proportions for the hydrogen production reaction; the unreacted methanol and the carbon monoxide produced by the MDR are used as make-up heat for the reactors and the high-pressure air before the turbine, while the exhaust waste heat supplies heat to the customer. The thermodynamic, economic and environmental performances of the system were investigated separately by developing a mathematical model describing the system. The results show that under the design conditions, the system has an energy storage density of 12.00 kWh/m3, an energy efficiency of 88.47 %, an exergy efficiency of 77.04 %, a lifetime net present value of 59.20 M$, a payback period of 4 years, and a CO2 emission per unit of energy output of 227.85 kg/MWh. Increasing the thermostatic heat source temperature and increasing the reactor diameter and length increased the methanol conversion rate. Increasing heat exchange effectiveness of the heat exchanger and heat source temperature can all improve system thermodynamic and economic performance. The energy storage density, energy efficiency, net present value and profitability of the system varied parabolically with the reactor tube diameter. The system energy storage density had a maximum value of 12.03 kWh/m3 at a reactor diameter of 0.040 m.

Energy-efficient anodic reactions for sustainable hydrogen production via water electrolysis

Overall water splitting is considered as an effective technique for hydrogen (H2) production; however, it usually requires large operating voltage mainly due to the high equilibrium potential of the anodic oxygen evolution reaction (OER). Replacing OER with energy-saving anode reactions not only reduces the operating voltage for H2 production but also generates high-value-added chemicals or purifies wastewater. This review article provides an overview of the fundamental reaction principles of overall water splitting and typical energy-saving alternative anode reactions, including methanol oxidation, hydrazine oxidation, and urea oxidation reactions. Then, the preparation methods, regulation strategies, and composition/structure-performance relations of advanced catalysts for these energy-efficient H2 generation technologies are discussed. Finally, we propose the underlying challenges and perspectives for this promising field.

Noble-metal-free dual CuNi single-atom embedded in ultrathin ZnIn2S4 for efficient photocatalytic H2 evolution

Developing noble-metal-free dual-metal single-atom catalysts with rich active accessible sites and excellent catalytic activity is very meaningful and challenging, especially for photocatalytic hydrogen production reaction, which can significantly reduce the cost of photocatalytic technology application while reducing the use of noble metals. Herein, a novel noble-metal-free dual CuNi single-atom modified ZnIn2S4 (CuNiSA-ZIS) photocatalyst with high hydrogen production performance were successfully prepared by a hydrothermal method. The ZnIn2S4 with a spherical nanoflower structure is composed of ultrathin nanosheets, and ACHDDAF-STEM results shows that CuNi bimetallic particles are uniformly distributed on the surface of ZnIn2S4 nanosheets and exhibit atomic level dispersion, forming dual-metal single-atom structure. The optimized 1 wt% CuNiSA-ZIS photocatalyst with the Cu/Ni ratio of 1:1 shows the optimum H2 evolution performance with a rate of up to 7844.7 μmol·g−1·h−1 using triethanolamine as a sacrificial reagent, which is significantly improved compared to pristine ZIS, Cu-ZIS and Ni-ZIS samples under simulated sunlight. Electrochemical and spectroscopic characterization results demonstrated that the improved photocatalytic activity of CuNiSA-ZIS was mainly due to the addition of the dual CuNi single atoms with a synergistic effect served as a co-catalyst for ZnIn2S4 photocatalysts, providing efficient active sites for hydrogen evolution while preventing the fast recombination of photo-generated electrons and holes. This study provides a valuable source of ideas for the design of effective noble-metal-free dual-metal single-atom catalysts.

Stacked ZnS multilayers of ZnS(en)0.5 hybrids with enhancing photocatalytic performance for H2 production

Zinc sulfide hybrids with different stacked ZnS multilayers were prepared using a chemical precipitation method in a solvent mixture of Ethylenediamine:Water:Butanol via two routes - nitrate and acetate salt precursors. The impact of butanol solvent contents (30 and 60 vol%) on the formation of orthorhombic-ZnS(en)0.5 hybrid with different stacking of ZnS layers was comprehensively analyzed using X-ray diffraction, Fourier Transform Infrared, X-ray photoelectron spectroscopy, and diffuse reflectance spectroscopy. Scanning electron microscopy was employed to study the influence of the mixture solvent on particle size and morphology of the resulting ZnS(en)0.5 hybrid micro flakes or nanosheets. The photocatalytic response was evaluated through hydrogen production reactions using low photocatalyst load under UV light irradiation, conducted over four reaction cycles. A significant increase in hydrogen production rate (4.6 and 4.0 times more active) was achieved for the exfoliated ultrathin nanosheet ZnS(en)0.5 hybrid prepared with lower butanol contents from the nitrate and acetate route, respectively. This enhancement was attributed to the reduced size of the nanosheets of stacked ZnS multilayers, which resulted from the incorporation of 30 vol% of butanol during the synthesis. Overall, the findings indicate that the Ethylenediamine:Butanol solvent system plays a crucial role in tuning the degree of ZnS stacking layers, the particle size, and morphology of ZnS(en)0.5 hybrids, leading to improved photocatalytic performance in hydrogen production reactions.

In-situ construction of TiO2 polymorphic junction nanoarrays without cocatalyst for boosting photocatalytic hydrogen generation

There are significant challenges in developing technologies for high-yield photocatalytic hydrogen production reactions. Current photocatalytic materials face three key problems: low utilization of light, rapid recombination of photogenerated electron-hole pairs, and a limited number of active sites during photocatalytic reactions. As a result, these materials only improve one or two of the three steps involved in photocatalytic hydrogen production reactions. Consequently, achieving simultaneous multifunctional synergy to enhance the efficiency of all three processes is difficult. Here, we report an in situ dissolution-recrystallisation approach to design and fabricate a three-dimensional TiO2 rutile/anatase (AE-TiO2) array photocatalytic material for photocatalytic hydrolysis applications. It is shown that the unique 3D nanoarray structure and in situ fabrication of the AE-TiO2 homojunction with synergistic effects among the components lead to an increase in light harvesting efficiency, charge transport separation efficiency and surface active sites, which remarkably improve the photocatalytic hydrolysis performance. The prepared AE-TiO2 homojunction materials realizes a maximal photoactivity of 4 μmol cm−2·h−1, which is 39 times larger than that of pure TiO2 rutile nanorods.

High-efficient sunlight-driven hydrogen production from methanol steam reforming on a novel photo-thermo-catalysis and thermo-catalysis dual-bed reactor

Sunlight-driven methanol-steam-reforming (MSR) reaction using solar energy promises efficient production and safe transportation of hydrogen energy while storing solar energy. However, the low efficiency of photo-reforming and the high cost of thermo-reforming, intrinsically due to limited usage of full-spectrum solar energy, pose a significant challenge to practical application. Here, we propose a sunlight-driven dual-bed photo-thermo-catalytic reactor (DBPTR) for high-efficient hydrogen production from MSR with the cascaded utilization of photo-thermo-catalysis (PTC) over Pt-CuO catalyst bed and thermo-catalysis (TC) over CuO/ZnO/Al2O3 catalyst bed, respectively. The experimental data verify that the overall solar-to-hydrogen (STH) efficiencies of DBPTR remarkably achieve 22.5% in the laboratory and 20.3% outdoors, respectively. These excellent performances are evidently attributed to the fact that our DBPTR could harvest the short-wave radiation (high-energy photons) in the PTC bed for photo-thermo-driven hydrogen production and confine the long-wave radiation (low-energy photons) in the TC bed for thermo-driven hydrogen production. Meanwhile, the proposed DBPTR has been proved to be scaled-up and operate under a reasonably concentrated irradiance of 16 kW m−2 with the above high STH efficiency, harmonizing the high-performance reactor, low-cost concentrator and moderate-accuracy sun-tracker. This work opens up a novel practical pathway towards high-efficient solar-to-chemical conversion.

Design and optimization of hydrogen production system model for dimethyl ether self-heating steam reforming

Hydrogen, as a clean energy source, has been widely used in the automotive industry. However, considering the difficulties of hydrogen storage and transportation, the in-situ production process has received increasing attention. In this paper, a hydrogen production system for dimethyl ether self-heating steam reforming is proposed, using a spiral tube reactor in which the oxidation of dimethyl ether occurs in the spiral tube, and the exothermic oxidation of dimethyl ether is used to provide heat for the dimethyl ether steam reforming hydrogen production reaction. A numerical model of the hydrogen production system for dimethyl ether self-heating reforming is developed, the model is simulated and analyzed, the accuracy of the model is verified through experiments, the influence of various parameters and on the system is analyzed, and the system is optimized. The results show that the proposed system can solve the problems of high energy consumption, low hydrogen yield and difficult reaction control faced by traditional autothermal reforming hydrogen production, and the system can achieve 87.79% dimethyl ether conversion rate, 84.94% hydrogen yield and 85.94% system thermal efficiency.

Study on the Influence of Surface Integrity on Hydrogen Permeation Resistance of Hydrogen Production Reactor Materials

Hydrogen permeation reduces a material’s properties and increases the risk of brittle fracture, which causes a potential safety hazard. A workpiece’s hydrogen permeation resistance could be improved by improving its surface integrity through surface processing. This paper studies low-alloy steel’s surface integrity and its hydrogen permeation resistance in a hydrogen production reactor, using the electrochemical cathodic hydrogen-charging method to carry out electrochemical hydrogen-charging experiments. After the specimens were pretreated using different surface-grinding methods and shot peening pressure strengthening, they were hydrogen-charged on a self-designed and built electrolytic hydrogen charging platform. Before and after hydrogen charging, the specimens’ section hardness and tensile strength were tested, and the fracture morphology of the specimens was observed. The influence laws of surface roughness and surface residual compressive stress on the distribution of material hardness along the depth, the variation in material hardness, the fracture morphology, and the decline in the tensile properties of the low-alloy steel specimens after 5 h of hydrogen charging were analyzed. The reasons for the influence of surface integrity indexes on the hydrogen permeation resistance of the specimens were also analyzed. Based on the experimental results, a series of mechanical processing parameters were proposed to improve the material’s permeation resistance, which provides a theoretical and practical basis for the processing of materials with high surface integrity and hydrogen permeation resistance. Through the experiments, it was found that the hydrogen permeation resistance of the Ra 0.17 μm surface roughness specimen was the best of all specimens with different surface roughness values, and its hydrogen embrittlement sensitivity index was 20.96%. The specimen had the best hydrogen permeation resistance under 336 MPa surface residual compress stress, and its hydrogen embrittlement sensitivity index was 16.45%.

Simulation Analysis of Methane Exhaust Reforming Mechanism Based on Marine LNG Engine

LNG is a potential alternative fuel for ships. Generating H2 through exhaust reforming is an effective method to improve the performance of the LNG engine and reduce its pollutant emissions. It is necessary to study the mechanism of methane exhaust reforming to guide the design of the reformer. Based on the detailed mechanism, the characteristics of methane reforming reaction were studied for a marine LNG engine. Firstly, the reforming characteristics of exhaust were studied. The results show that methane reforming requires a lean oxygen environment, and the hydrogen production reaction will not occur when the O2 concentration is too high. Then, the effects of the O2/CH4 ratio (0.2–1) and H2O/CH4 ratio (0–2) on the reforming reaction were studied. The results show that under O2/CH4 = 0.4, the molar fraction of hydrogen at the outlet of the reactor decreases with the increase in the H2O/CH4 ratios. Finally, a mechanism analysis was conducted. The results show that an oxidation reaction occurs first and then the steam reforming reaction occurs on palladium-based catalysts.

Effect of noble gases on the transport and thermodynamic characteristics of microchannel reforming reactors for hydrogen production

Noble gases can offer the advantages of high selectivity in steam reforming processes with especially great potential for hydrogen production, but the underlying cause for process intensification has not yet been identified. Calculations are performed to investigate the effect of helium or argon gases on the transport and thermodynamic characteristics of a microchannel reactor for hydrogen production. Dimensionless Nusselt and Sherwood number analyses are carried out and the thermodynamic properties of the reaction mixture are determined in order to effectively control the heat and mass transport processes with increasing precision. The heat and reaction phenomena in the reactor system are studied in order to understand the underlying cause for the improvements in transport performance. Enthalpy analysis is performed and the evolution of energy in the chemical processes is discussed based upon reaction heat flux. The results indicate that the noble gas offers the advantages of process intensification due to enhanced heat and mass transport. Additionally, the noble gas can be utilized to enhance conversion behavior while maintaining the reaction rate. Furthermore, the transport properties can be effectively controlled and manipulated, thereby serving as a means for improving the effectiveness of convection at the catalyst surface. Additional advantages include the ability to avoid the problem inherent in thermal management, thereby providing nearly isothermal operation and thus suppressing undesirable side reactions. Finally, the reforming process is characterized for purposes of demonstration or explanation by thermodynamic parameters, including temperature, specific heat, specific enthalpy, sensible enthalpy, and mean molecular weight.

Rational Construction of Electrostatic Self‐Assembly of Metallike MoP and ZnIn2S4 Based on Density Functional Theory to Form Schottky Junction for Photocatalytic Hydrogen Production

It is an effective strategy to construct a photogenerated carrier‐transfer channel based on the load between photocatalysts to improve the light‐absorption capacity and separation efficiency of a single photocatalyst. In this work, the MoP is embedded on the surface of ZnIn2S4 through electrostatic self‐assembly to form ZnIn2S4/MoP‐20%, the hydrogen production performance is 151.93 μmol in 5 h, and is 13 times that of ZnIn2S4, which greatly improves the hydrogen production performance of ZnIn2S4. Based on density functional theory (DFT) calculation, MoP with metallike properties and semiconductor ZnIn2S4 with indirect bandgap successfully constructed Schottky junction. MoP acts as the active site in hydrogen production system and accepts photogenerated electrons through Schottky junction, which can effectively accelerate the separation of electron–hole pairs and enable more effective photogenerated electrons to participate in photocatalytic hydrogen production reaction. In this experiment, a new method is provided for the development of Schottky junction based on DFT calculation to efficiently use solar photocatalytic water to produce hydrogen.

Solar-driven multichannel membrane reactor for hydrogen production from ammonia decomposition

Solar-driven ammonia decomposition is one of the most promising carbon-free pathways to release hydrogen from ammonia. Enhancing the heat and mass transfer processes within an ammonia decomposition membrane reactor is crucial to improve the hydrogen production rate. The multichannel reactors can reduce hydraulic diameters by raising the number of channels while the lateral surface areas of reactors keep the same, which can enhance heat and mass transfer without enlarging re-radiation losses. In this paper, a solar-driven multichannel membrane reactor for ammonia decomposition is proposed, which is promising to improve the conversion without deteriorating the efficiency. Models are developed to simulate the proposed multichannel membrane reactor under solar irradiation. A multichannel membrane reactor with three Pd membrane channels is designed and built. Experiments have been conducted to validate the reactor model. With the validated model, two consecutive parametric studies have been conducted for catalyst volume decreasing and increasing scenarios, respectively. The results show that enlarging permeation area by increasing membrane channels is worthwhile to improve the conversion although the catalyst volume decreases. Under the same solar flux and inlet ammonia properties, a six-channel membrane reactor can achieve a conversion of 0.76, while a single-channel membrane reactor can only achieve a conversion of 0.49. Additionally, the maximum temperature difference within the six-channel reactor is 47 °C lower than that within single-channel membrane reactor, which is favorable for the Pd membrane operating temperature range.

A parametric computational-fluid-dynamics study on improving the performance of a flat membrane reactor for on-site hydrogen production

Hydrogen stations have limited geographic coverage despite the rising demand for fuel cell electric vehicles. An on-site hydrogen production system that utilizes the liquid-fuel infrastructure can improve access to hydrogen in remote areas. The system has a pressurized steam reformer to convert the liquid fuel and a catalytic membrane reactor to produce high-purity hydrogen. This comprehensive computational-fluid-dynamics study aims to enhance the performance of the membrane reactor. We validate our models of a water-gas-shift catalyst reactor, the membrane reactor with high-purity hydrogen, and the same reactor loaded with the catalyst. The flow configuration, inlet, and outlet of the reactor are then changed to enhance the performance. We enlarge the membrane area at constant catalyst volume and observe 97% of the maximum hydrogen permeation at 38.5 cm2. This work is significant because it describes a step-by-step approach to improving the performance of a given reactor for future studies of membrane-reactor design.

Hollow rod-shaped Cu-In-Zn-S@ZnCo2O4@In2O3 tandem heterojunction for efficient visible light-induced photocatalytic hydrogen production

Photocatalytic hydrogen production technology is an efficient method to solve the environmental pollution problem and obtain renewable energy. To improve the hydrogen production efficiency, it is still a great challenge to develop novel photocatalysts with high activity and high stability. In this work, a hollow rod-shaped Cu-In-Zn-S@ZnCo2O4@In2O3 tandem heterojunction photocatalyst was designed and synthesized. Under visible light irradiation, the photocatalytic hydrogen production amount was up to 21404.54 μmol·g−1 in 5 h. The hollow tandem heterojunction would improve the light absorption, facilitate the electron transfer, inhibit the recombination of photogenerated electrons and holes, and provide more active sites for hydrogen production reaction. The design of Cu-In-Zn-S@ZnCo2O4@In2O3 photocatalyst provided an effective method to enhance the photocatalytic hydrogen production performance.

Comprehensive study on catalytic coating tubular reactor with electromagnetic induction heating for hydrogen production through methanol steam reforming

This study presents an induction heating-based reactor for on-board methanol steam reforming for hydrogen production reactors and distributed hydrogen refueling stations, with the goal of developing a hydrogen production process with zero carbon emissions. The numerical results showed that the enhanced hydrogen production performance and temperature cold spots could be eliminated, and the methanol conversion was close to 100%. at 150 A and 20 kHz. Induction heating may significantly shorten the reactor's cold start-up time. Under 50 kHz, the temperature of the reactor wall can reach more than 500 K in 50 s, in other words, induction heating overcomes the problems of slowly heating/cooling rate for on-board methanol steam reforming for hydrogen generation reactors. Overall, this study supports the feasibility of producing green hydrogen with zero carbon emissions for advancing the development of an environmental hydrogen economy and the cold start-up of distributed hydrogen energy and vehicle-used hydrogen production equipment.

A Review: Membrane Reactor for Hydrogen Production: Modeling and Simulation

A membrane reactor is a multifactional vessel used for H2 production. Hydrogen's three spectrum colors are dependent on carbon present. Two types of membrane with high permeability to hydrogen (polymeric and metallic) Hydrogen is produced in two systems: conventional reactors and membrane reactors (which separate and purify hydrogen in a single vessel). There are many types of membrane reactors according to design (catalytic membrane reactor (CMR), fixed bed reactor (FBMR), fluidized bed reactor (FBMR), etc. The transport mechanism of H2 through the membrane by a "sorption-diffusion mechanism" and the government equations that are used for membrane reactor modeling and simulation, such as continuity, momentum, mass, and heat transfer equations of the CMR, and the thickness of the membrane. These equations are solved by MATLAB, COMSOL, and the Finite Element Method to simulate the MR at different parameters: rate of conversion, rate of sweep gas, temperature, pressure, rate of H2 permeation through a membrane, and activity of the catalyst. We summarized theoretical studies for membrane reactors, including the operation conditions, type of hydrocarbon feed, type of production method, kind of catalyst, and heat effect.

Self-catalytic nickel hollow fiber membrane reactor for hydrogen production via toluene steam reforming

Metal-nickel membrane exhibits good H2 separation performance and inherent catalytic activity, making it a promising candidate as a membrane reactor in the simultaneous catalytic reforming of hydrocarbons and H2 separation. In this work, nickel hollow fiber membranes were fabricated using a spinning/sintering technology and subsequently employed in a membrane reactor for toluene steam reforming and H2 separation. The catalytic H2 production and permeation performance of the toluene steam reforming (TSR) hollow fiber membrane reactor were investigated under varying conditions, such as temperature, feed flow rate, steam-to-carbon ratio (S/C). The results show that toluene can be fully converted with a toluene feed flow rate of 1.5 μL min−1. Increasing S/C can enhance the H2 production, but excessive steam will lead to a decrease of the H2 permeation flux. The H2 yield and H2 permeation flux are 24.2% and 4.35 mmol m−2 s−1, respectively, under the conditions of S/C = 3, Ar = 90 mL min−1 and N2 = 3 mL min−1 at a temperature of 950 °C. The H2 yield and H2 permeation flux of the TSR membrane reactor did not significantly decrease within 96 h. In addition, the membrane reactor can operate stably within 62 h in an atmosphere containing 1000 ppm H2S.

Enhanced hydrogen production coupled with ethanol electrocatalytic oxidation by flow-through self-supporting electrode

Electrocatalytic oxidation of ethanol to value-added production is an ideal replacement of the conventional anodic oxygen evolution reaction (OER) for efficient hydrogen (H2) production due to the lower electric potential energy and higher safety. However, the sluggish mass transfer rate of reactants commonly is the crucial limitation of electrocatalytic oxidation efficiency. Here, Ni(OH)2 nanosheet is immobilized on nickel foam (NF) to fabricate a flow-through self-supporting electrode (Ni(OH)2/NF) served as anode for ethanol electrocatalytic oxidation, in coupling with high-purity H2 production at the cathode. The potential for electrocatalytic oxidation of ethanol and H2 evolution was significantly reduced by 200 mV compared to pure water splitting at 25 mA cm−2. The boundary layer thickness on the anodic electrode surface could be decreased from 86.66 μm to 66.21 μm with the flow rate increased from 0 to 0.82 cm min−1. Compared to the batch mode, The conversion rate of ethanol can be increased from 59 % to 100 % and the selectivity of acetic acid can be increased from 88 % to 100 % under the flow-through mode. The Faraday efficiency of the anode achieved an increase from 76 % to over 99 % and the H2 production of the cathode increased by 31 % under the flow-through mode.

Correlating the Valence State with the Adsorption Behavior of a Cu-Based Electrocatalyst for Furfural Oxidation with Anodic Hydrogen Production Reaction.

The low-potential furfural oxidation reaction (FFOR) on a Cu-based electrocatalyst can produce H2 at the anode, thereby providing a bipolar H2 production system with an ultra-low cell voltage. However, the intrinsic activity and stability of the Cu-based electrocatalyst for the FFOR remain unsatisfactory for practical applications. This study investigates the correlation between the valence state and the adsorption behavior of the Cu-based electrocatalyst in furfural oxidation. Cu0 is the adsorption site with low intrinsic activity. Cu+ , which exist in the form of Cu(OH)ads in alkaline electrolyte, has no adsorption ability but can improve the performance of Cu0 by promoting adsorption of FF. Moreover, a mixed-valence Cu-based electrocatalyst (MV Cu) with high intrinsic activity and stability is prepared electrochemically. With the MV Cu catalyst, the assembled dual-side H2 production electrolyzer has a low electricity requirement of only 0.24 kWh·mH2 -3 at an ultra-low cell voltage of 0.3V, and it exhibits sufficient stability. This study not only correlates the valence state with the adsorption behavior of the Cu-based electrocatalyst for the low-potential FFOR with anodic H2 production but also reveals the mechanism of deactivation to provide design principles for Cu-based electrocatalysts with satisfactory stability. This article is protected by copyright. All rights reserved.

Rational design of ZnCdS/TpPa-1-COF heterostructure photocatalyst by strengthening the interface connection in solar hydrogen production reactions

Rational design of ZnCdS/TpPa-1-COF heterostructure photocatalyst by strengthening the interface connection in solar hydrogen production reactions