Hydrogen Production Capacity Research Articles

Study of the Structural Changes and Internal Activator Transport Behavior after Activation of Aluminum-Based Flameless Ration Heaters: Experimental and Molecular Dynamics Simulations.

Aluminum-based flameless ration heaters (AFRHs) are heating elements in food packaging. Water is used to activate AFRHs. The material properties of each region of AFRHs were determined by X-ray diffraction, scanning electron microscopy, and hydrogen and heat generation. The results show that the internal cross-section shows stratification with hydrogen and heat production capacities of 105.2 ± 9.7 mL/g and 1435.0 ± 30.3 J/g for the outer layer, 27.1 ± 4.4 mL/g and 80.4 ± 3.1 J/g for the inner layer, and 1.1 ± 0.01 mL/g and 1.2 ± 0.05 J/g for the middle layer, respectively. According to the correspondence between aluminum and hydrogen in the aluminum-water reaction relationship, the reaction efficiency of the outer layer and the inner layer is as low as 64 and 80%, which is an indication of low reaction efficiency. To analyze the reasons for low reaction efficiency, a pore channel model of 3.5 nm tricalcium aluminate (C3A) was developed using molecular dynamics (MD) to reveal the adsorption behavior of the activator in the pore channel. The results show that the activator is subject to solid surface adsorption in the pore channel with a low diffusion coefficient. Oxygen atoms on the surface adsorb hydrogen atoms to form hydrogen bonds and sodium ions to form ionic bonds with calcium ions. This increases the retention time of the activator on the surface. The MD results explain the low reaction efficiency of AFRHs at the microscopic scale. Moreover, it provides ideas and a basis for the optimization of AFRHs.

Assessing feasible H2–CO2 sources in the US as Feedstocks for Sustainable Aviation Fuel Precursors: Acetic Acid and Ethanol Production via Hydrogenotrophic Pathways

The environmental impact of carbon dioxide emissions is significant, and research is focused on mitigating these emissions and developing eco-friendly technologies in line with green chemistry principles. Waste-to-energy technologies play a crucial role in converting waste into renewable energy and valuable biofuels and bioproducts. This study specifically explores the utilization of waste gas emissions, particularly carbon dioxide, from various sources in the United States for the production of sustainable aviation fuel (SAF) precursors, such as ethanol and acetic acid. The study categorizes and quantifies the volumes of carbon dioxide emissions into three types: non-biogenic, biogenic, and biogenic emissions from ethanol production facilities. Stoichiometric calculations are applied to compare the amounts of carbon dioxide from each category with the available hydrogen production capacity, determining if sufficient hydrogen is present for converting carbon dioxide into SAF precursors. The study reveals two key findings. Firstly, there is a significant reserve of carbon dioxide, approximately 1648 million metric tons per year (MMTy), combining all three categories, which would require a substantial increase of approximately 35–40 times in the existing hydrogen production capacity of 4.988 MMTy. This increased hydrogen production has the potential to yield approximately 1067.82 MMTy of acetic acid and 189.19 MMTy of ethanol annually. Secondly, upon analyzing the quality and application of the three sources of carbon dioxide with the currently available hydrogen production capacity, it is found that biogenic carbon dioxide from ethanol plants is the most suitable choice for immediate production of SAF precursors. This would theoretically result in an annual production of 1.36 MMTy of ethanol and 1.772 MMTy of acetic acid. The other two sources of carbon dioxide can be considered potential reserves for future utilization when additional hydrogen production facilities are established.The study provides a foundation for assessing the aggregation potential required for acetic acid and ethanol production. By optimizing the use of waste gases as raw materials, the study not only enables the production of SAF precursors but also contributes to the passive reduction of greenhouse gas emissions.

Oxygen Vacancies Defective La2Ti2O7 Nanosheets Enhanced Photocatalytic Activity of Hydrogen Evolution under Visible Light Irradiation.

A novel and efficient technique has been designed for the creation of oxygen vacancies on La2Ti2O7 (LTO) nanosheets. This is achieved via a controlled solid-state reaction between NaBH4 and LTO nanosheets. Transmission electron microscopy (TEM) analyses expose that these processed LTO specimens possess a unique crystalline core/amorphous shell structure, represented as La2Ti2O7@La2Ti2O7-x. According to X-ray photoelectron spectroscopy (XPS) observations, there is a notable correlation between the reaction time, temperature, and the concentration of oxygen vacancies. The concentration of these vacancies tends to increase along with the reaction time and temperature. Concurrently, UV-Visible spectra and photocatalytic tests reveal a significant impact of oxygen vacancies on the LTO surface on both light absorption and photocatalytic functionality. Most notably, the LTO nanosheets with engineered oxygen vacancies have demonstrated an exceptional photocatalytic capacity for hydrogen production under visible light. The maximal activity recorded was an impressive 149 μmol g-1 h-1, which is noticeably superior to the performance of the pristine La2Ti2O7.

The effect of substrate acidification on the biohydrogen production by dark fermentation

The modification of substrate concentration and acidification level in inoculum treatment can significantly enhance hydrogen production while reducing costs. Hydrogen production showed a significant variation with food waste (FW) concentration, ranging from 10 to 120 gVS/L. Insufficient acidity at lower FW concentrations of 10, 20, and 40 gVS/L limited hydrogen production to 9.14, 5.70, and 7.78 mL/gVS, respectively, hindering hydrogen-producing bacteria dominance. However, higher FW concentrations facilitated rapid and strong substrate acidification at fermentation onset, effectively inhibiting the non-hydrogen producing bacteria and leading to a vast hydrogen production capacity of 68.63–120.78 mL/gVS. Rapid and substantial FW acidification is vital for effective inoculum treatment, highlighting its crucial role in this study. The findings support the potential use of FW inoculum treatment in generating highly productive microbial communities for hydrogen production.

Technoeconomic Analysis for Green Hydrogen in Terms of Production, Compression, Transportation and Storage Considering the Australian Perspective

This current article discusses the technoeconomics (TE) of hydrogen generation, transportation, compression and storage in the Australian context. The TE analysis is important and a prerequisite for investment decisions. This study selected the Australian context due to its huge potential in green hydrogen, but the modelling is applicable to other parts of the world, adjusting the price of electricity and other utilities. The hydrogen generation using the most mature alkaline electrolysis (AEL) technique was selected in the current study. The results show that increasing temperature from 50 to 90 °C and decreasing pressure from 13 to 5 bar help improve electrolyser performance, though pressure has a minor effect. The selected range for performance parameters was based on the fundamental behaviour of water electrolysers supported with literature. The levelised cost of hydrogen (LCH2) was calculated for generation, compression, transportation and storage. However, the majority of the LCH2 was for generation, which was calculated based on CAPEX, OPEX, capital recovery factor, hydrogen production rate and capacity factor. The LCH2 in 2023 was calculated to be 9.6 USD/kgH2 using a base-case solar electricity price of 65–38 USD/MWh. This LCH2 is expected to decrease to 6.5 and 3.4 USD/kgH2 by 2030 and 2040, respectively. The current LCH2 using wind energy was calculated to be 1.9 USD/kgH2 lower than that of solar-based electricity. The LCH2 using standalone wind electricity was calculated to be USD 5.3 and USD 2.9 in 2030 and 2040, respectively. The LCH2 predicted using a solar and wind mix (SWM) was estimated to be USD 3.2 compared to USD 9.6 and USD 7.7 using standalone solar and wind. The LCH2 under the best case was predicted to be USD 3.9 and USD 2.1 compared to USD 6.5 and USD 3.4 under base-case solar PV in 2030 and 2040, respectively. The best case SWM offers 33% lower LCH2 in 2023, which leads to 37%, 39% and 42% lower LCH2 in 2030, 2040 and 2050, respectively. The current results are overpredicted, especially compared with CSIRO, Australia, due to the higher assumption of the renewable electricity price. Currently, over two-thirds of the cost for the LCH2 is due to the price of electricity (i.e., wind and solar). Modelling suggests an overall reduction in the capital cost of AEL plants by about 50% in the 2030s. Due to the lower capacity factor (effective energy generation over maximum output) of renewable energy, especially for solar plants, a combined wind- and solar-based electrolysis plant was recommended, which can increase the capacity factor by at least 33%. Results also suggest that besides generation, at least an additional 1.5 USD/kgH2 for compression, transportation and storage is required.

Design and operation performance of the plate-heat transfer type hydrogen production reactor for bio-methanol reforming

In this paper, the plate-heat transfer type bio-methanol steam reforming reactor for hydrogen fuel cell vehicles and its operation performance was studied. The structure of the plate-heat transfer type for bio-methanol reforming has been designed and optimized with the application parameters of hydrogen production capacity, hydrogen production rate, bio-methanol conversion rate, volume limitation. Results showed the catalyst particle size has little influence when it less than 0.85 mm; However, when the catalyst loading was 20 g and the feed rate of bio-methanol solution was 1.5 mL/min, the effect of reforming bio-methanol was the best. At this time, the specific hydrogen production was 64.062 mL/gcat.min, the hydrogen production rate was 21.354 mL/s, the bio-methanol conversion rate was 82.25%. This paper can provide scientific reference for further research and development of high-efficiency and low-cost bio-methanol reforming hydrogen production equipment.

Investigation on environmental stability and hydrolytic hydrogen production behavior of Mg30La alloy modified by activated carbon/expandable graphite

In the process of hydrogen production, Mg-based alloy is easily poisoned by the environment to form an inert oxide layer. The effect of carbon catalysts (AC、EG) on the environmental stability of short time high energy ball milling Mg30La alloy is explored by simulating the real environmental toxic conditions. The toxicity of Mg30La alloy with oxygen and oxygen without water and the anti-toxicity ability after surface modification are reported. The results show that Mg30La alloy has the highest initial hydrogen production rate before exposure, and the average rate is 88.66 mL g−1·min−1 in the first 5 min. But Mg30La-EG has a higher yield, reaching 91% at 60 min, 18% higher than that of Mg30La alloy without catalysis. The yield of Mg30La-AC is only 55% at 60 min. After the sample is exposed, the hydrolyzed hydrogen production test show that Mg30La-EG has a higher initial hydrogen production rate than Mg30La, reaching 87.5 mL g−1·min−1 in the first 2 min. However, Mg30La alloy has the highest hydrogen production capacity, 21% higher than Mg30La-AC and 20% higher than Mg30La-EG. In summary, after adding AC, the adsorption of activated carbon will lead to the formation of an inert layer on the surface, thus affecting the hydrolytic hydrogen production performance. However, after adding EG, hydrogen can be rapidly produced at room temperature, and the yield of Mg30La alloy can be significantly improved. However, long-term contact with the environment should be avoided before hydrogen production to ensure low temperature, rapid and efficient hydrogen production.

Hydrogen production from an on-board reformer for a natural gas engine: A thermodynamics study

In the present study, for an insight into the optimizing windows of comprehensive energy efficiency for open-loop system of marine NG engine and reformer, a peculiar thermodynamic equilibrium model for simulating the exhaust gas-fuel reforming process is established using equilibrium constant and experimental results. The accuracy of the model is evaluated by comparing numerical simulations with data derived from experiment of the open-loop operation system. Accordingly, the effect of engine loads and excess air (λ) as well as reformer feedstocks on maximum theoretical reforming characteristics are investigated. In addition, the energetic distribution in open-loop operation system can be clarified by the first law of thermodynamic. The results shown that fuel conversion toward H2 is highly selective due to the enhancement of reaction temperature with increasing engine loads. Especially, under 75% engine load, the maximum theoretical H2 yield reaches up to approximately 42.3% when λ = 1.4, CH4/O2 (M/O) = 1.5 and H2O/CH4 (S/M) = 2; The high λ will dilute the feed concentration of the reformer, thereby inhibiting the reforming reaction moving toward H2 production. Hence, an appropriate λ (1.4) can maximize the hydrogen production capacity of the reformer. In addition, according to the energy distribution of the open-loop system, the theoretical reforming energy efficiency of the reformer reaches a peak of 93.5% at S/M = 2 and M/O = 5. However, it can be found that M/O should be maintained above 1.5 to acquire optimal reforming energy utilization efficiency of system. Summarily, the optimal operation conditions for the reformer in open-loop operation system are confirmed: M/O = 1.5–2.5 and S/M = 1.5–2 under 75% engine load, which could fulfill efficient reforming performance.

Activating and optimizing MoS2 basal-plane via spontaneous oxidation for enhanced photocatalytic hydrogen generation

MoS2 is a promising photocatalyst for hydrogen evolution reaction (HER), but its performance is still poor when used directly as a photocatalyst, due to its poor conductivity and high carrier recombination ratio. Here, through first-principles calculations, we find that spontaneous oxidation of the base plane can optimize the photocatalytic performance of MoS2. The MoS2−xOx crystal formed by spontaneous oxidation on the base plane results in an order of magnitude difference in electron-hole effective mass, and the electrostatic potential difference caused by symmetry breaking further promotes the effective separation of electron-hole pair, thus optimizing the photocarrier recombination rate of MoS2. In addition, with the increase of the degree of spontaneous oxidation, MoS2 bandgap continues to decrease, improving the intrinsic conductivity and visible light utilization. By comparing the REDOX potential of water splitting and the relative position of the band-edge in the neutral environment, the conduction band-edge of MoS2−xOx can meet the energy level requirements of photocatalytic HER until the doping concentration is 12.5%, and the high hydrogen production capacity has been reserved. Therefore, MoS2−xOx formed by spontaneous oxidation is an efficient and convenient photocatalyst with potential application prospect.

Current Development Status, Policy Support and Promotion Path of China’s Green Hydrogen Industries under the Target of Carbon Emission Peaking and Carbon Neutrality

The green hydrogen industry, highly efficient and safe, is endowed with flexible production and low carbon emissions. It is conducive to building a low-carbon, efficient and clean energy structure, optimizing the energy industry system and promoting the strategic transformation of energy development and enhancing energy security. In order to achieve carbon emission peaking by 2030 and neutrality by 2060 (dual carbon goals), China is vigorously promoting the green hydrogen industry. Based on an analysis of the green hydrogen industry policies of the U.S., the EU and Japan, this paper explores supporting policies issued by Chinese central and local authorities and examines the inherent advantages of China’s green hydrogen industry. After investigating and analyzing the basis for the development of the green hydrogen industry in China, we conclude that China has enormous potential, including abundant renewable energy resources as well as commercialization experience with renewable energy, robust infrastructure and technological innovation capacity, demand for large-scale applications of green hydrogen in traditional industries, etc. Despite this, China’s green hydrogen industry is still in its early stage and has encountered bottlenecks in its development, including a lack of clarity on the strategic role and position of the green hydrogen industry, low competitiveness of green hydrogen production, heavy reliance on imports of PEMs, perfluorosulfonic acid resins (PFSR) and other core components, the development dilemma of the industry chain, lack of installed capacity for green hydrogen production and complicated administrative permission, etc. This article therefore proposes that an appropriate development road-map and integrated administration supervision systems, including safety supervision, will systematically promote the green hydrogen industry. Enhancing the core technology and equipment of green hydrogen and improving the green hydrogen industry chain will be an adequate way to reduce dependence on foreign technologies, lowering the price of green hydrogen products through the scale effect and, thus, expanding the scope of application of green hydrogen. Financial support mechanisms such as providing tax breaks and project subsidies will encourage enterprises to carry out innovative technological research on and invest in the green hydrogen industry.

Development and assessment of a novel multigeneration plant combined with a supercritical CO2 cycle for multiple products

Multigenerational energy conversion plants are one of the most promising solutions for tackling environmental challenges and making efficient use of energy sources. In this regard, a newly designed multigeneration plant integrated with a methane-based Brayton cycle, a steam Rankine cycle, a supercritical CO2-based Brayton cycle, a multi-effect desalination process, a PEM unit, a domestic water heater process, and two thermoelectric generators is integrated, proposed and analyzed. The thermodynamic and environmental assessments of the developed paper are conducted and examined with energy and exergy efficiencies as well as CO2 emission rate. Similarly, a parametric study is executed and reported, by the way, to define the impact of the various significant factors on the developed plant's efficiency. In the end, the CO2 emission rate is determined and compared according to different energy conversion plants. In light of the analysis results, the net power, hydrogen, and freshwater production capacities of the reference study are calculated to be 1336 kW, 0.002004 kgs−1, and 0.954 kgs−1, respectively. Additionally, it is found that the developed study's energetic and exergetic performances are 55.76% and 52.17%. According to emission analysis results, the multigeneration system emits 272.2 kg/MWh less CO2 emissions than the single energy conversion system.

Recent Progress on Hydrogen-Rich Syngas Production from Coal Gasification

Coal gasification is recognized as the core technology of clean coal utilization that exhibits significant advantages in hydrogen-rich syngas production and CO2 emission reduction. This review briefly discusses the recent research progress on various coal gasification techniques, including conventional coal gasification (fixed bed, fluidized bed, and entrained bed gasification) and relatively new coal gasification (supercritical water gasification, plasma gasification, chemical-looping gasification, and decoupling gasification) in terms of their gasifiers, process parameters (such as coal type, temperature, pressure, gasification agents, catalysts, etc.), advantages, and challenges. The capacity and potential of hydrogen production through different coal gasification technologies are also systematically analyzed. In this regard, the decoupling gasification technology based on pyrolysis, coal char–CO2 gasification, and CO shift reaction shows remarkable features in improving comprehensive utilization of coal, low-energy capture and conversion of CO2, as well as efficient hydrogen production. As the key unit of decoupling gasification, this work also reviews recent research advances (2019–2023) in coal char–CO2 gasification, the influence of different factors such as coal type, gasification agent composition, temperature, pressure, particle size, and catalyst on the char–CO2 gasification performance are studied, and its reaction kinetics are also outlined. This review serves as guidance for further excavating the potential of gasification technology in promoting clean fuel production and mitigating greenhouse gas emissions.

Large-scale green hydrogen production via alkaline water electrolysis using solar and wind energy

The study provided a precise technique for comparing wind and solar solutions for large-scale production of green hydrogen. A one-year experimental dataset depicting the wind speed and solar irradiance with a precision of 1 min. The carbon footprint study was conducted, and indicators were applied and evaluated for the purpose of standardising the performance assessment technique for renewable-based hydrogen production systems, such as the electrolyser capacity fulfilled by wind turbines and solar photovoltaic power plants. On the basis of the considered capacities of 2.5 for wind turbines and solar photovoltaics for cost estimating findings, the obtained optimum electrolyser capacity can match the energy produced by the wind turbine power plant, which is 1.5 MW, which can produce hydrogen at a rate of about 11,963 kg/year at 8.87$/kg, and the obtained optimum electrolyser capacity can match the energy produced by the solar photovoltaics power plant, which is 2.0 MW, which can produce hydrogen at a rate of about 94,432 kg/year at 6.33 $/kg. Further, the polynomial relation between hydrogen production and electrolyser capacity has been destroyed. The method used is easily adaptable for testing large-scale applications such as industrial plants, as well as any hydrogen requirements and environmental conditions.

Premier, Progress and Prospects in Renewable Hydrogen Generation: A Review

Renewable hydrogen production has an opportunity to reduce carbon emissions in the transportation and industrial sectors. This method generates hydrogen utilizing renewable energy sources, such as the sun, wind, and hydropower, lowering the number of greenhouse gases released into the environment. In recent years, considerable progress has been made in the production of sustainable hydrogen, particularly in the disciplines of electrolysis, biomass gasification, and photoelectrochemical water splitting. This review article figures out the capacity, efficiency, and cost-effectiveness of hydrogen production from renewable sources effectively comparing the conventionally used technologies with the latest techniques, which are getting better day by day with the implementation of the technological advancements. Governments, investors, and industry players are increasingly interested in manufacturing renewable hydrogen, and the global need for clean energy is expanding. It is projected that facilities for manufacturing renewable hydrogen, as well as infrastructure to support this development, would expand, hastening the transition to an environment-friendly and low-carbon economy.

Multiobjective optimization of a pressurized water reactor cogeneration plant for nuclear hydrogen production

In this paper, energy, exergy, economic analysis and multiobjective optimization of a pressurized water reactor (PWR) nuclear cogeneration plant for hydrogen production through high-temperature steam electrolysis (HTSE) are carried out. HTSE requires energy in the form of both heat and electrical work. A novel parameter, namely the heat/total energy ratio, is defined, and used as a decision variable in optimization. In addition to energy ratio, hydrogen production capacity, reactor thermal power, live steam temperature, reheating mass flow rate ratio, reheating temperature and steam extraction location are considered as the decision variables to simultaneously optimize the thermal efficiency, thermal-to-hydrogen efficiency, utilization factor, exergy efficiency and total revenue of the cogeneration plant. The analysis and optimization focus on the secondary cycle of the PWR and the effects of hydrogen and electricity prices and ambient conditions are also taken into account since these prices have a significant impact on the optimum design. For a hydrogen price of 4 $/kg and an electricity price of 0.1 $/kWh, when equal preference is given to all objective functions, the optimum production capacity is 6.778 kg/s. The energy ratio has an optimum value if the optimization focuses exclusively on the thermal efficiency and total revenue.

Theoretical insight into water splitting mechanism of B doped tri-s-triazine-based g-C3N4/m-BiVO4(001) heterojunction photocatalyst

We evaluated the geometrical, electrical, optical properties and charge transfer of pristine g-C3N4 (tri-s-triazine-based graphitic phase carbon nitride) B-doped g-C3N4 (doping of boron atoms into graphitic phase carbon nitride), m-BiVO4(001) surface (monoclinic bismuth vanadate (001) surface), g-C3N4/m-BiVO4(001) heterojunction and B-doped g-C3N4/m-BiVO4(001) heterojunction using density functional theory (DFT) simulations. Based on the findings, the synergistic impact of doping and heterojunctions on g-C3N4’s electronic properties as well as the photocatalytic mechanism of heterojunctions were analyzed. The doping of B atoms gives g-C3N4 a unique structure and reduces the effective mass of carriers, proving to be an effective way to increase electron transport capacity. The interfacial adhesion energy, binding energy, and interfacial distance all point to a van der Waals (vdW) interaction between g-C3N4 and m-BiVO4(001) surface. The findings demonstrate that the g-C3N4/m-BiVO4(001) heterojunction, in comparison to pristine g-C3N4 and m-BiVO4(001) surface, has a narrow bandgap, absorbs more photons and has a build-in electric field, all of which are advantageous for visible light-driven activity, the separation and transfer of charge carriers, and maintaining a strong redox ability. Additionally, the B-doped g-C3N4/m-BiVO4(001) heterojunction outperformed the g-C3N4/m-BiVO4(001) heterojunction in terms of visible light absorption efficiency, hydrogen production capacity, and interfacial charge density. The Z-scheme mechanism over the heterojunction has been proposed based on semiconductor theory to disclose the separation and transfer pathway of photogenerated charge during the photocatalytic water splitting process. The theoretical design provided here provides a theoretical reference for the efficient of g-C3N4-based photocatalysts for the efficient use of solar energy and the protection of the environment.

Thermal analysis of a micro tubular reactor for methanol steam reforming by optimizing the multilayer arrangement of catalyst bed for the catalytic combustion of methanolr

Packed bed tube reactors are commonly used for hydrogen production in proton exchange membrane fuel cells. However, the hydrogen production capacity of methanol steam reforming (MSR) is greatly limited by the poor heat transfer of packed catalyst bed. The hydrogen production capacity of catalyst bed can be effectively improved by optimizing the temperature distribution of reactor. In this study, four types of reactors including concentric circle methanol steam reforming reactor (MSRC), continuous catalytic combustion methanol steam reforming reactor (MSRR), hierarchical catalytic combustion methanol steam reforming reactor (MSRP) and segmented catalytic combustion reactor with fins (MSRF) are designed, modeled, compared and validated by experimental data. It was found that the maximum temperature difference of MSRC, MSRR, MSRP and MSRF reached 72.4 K, 58.6 K, 19.8 K and 11.3 K, respectively. In addition, the surface temperature inhomogeneity Uf and CO concentration of the MSRF decreased by 69.8% and 30.7%, compared with MSRC. At the same reactor volume, MSRF can achieve higher methanol conversion rate, and its effective energy absorption rate is 4.6%, 3.9% and 2.6% higher than that of MSRC, MSRR and MSRP, respectively. The MSRF could effectively avoid the influence of uneven temperature distribution on MSR compared with the other designs. In order to further improve the performance of MSRF, the influences of methanol vapor molar ratio, inlet temperature, flow rate, catalyst particle size and catalyst bed porosity on MSR were also discussed in the optimal reactor structure (MSRF).

Exergoeconomic performance evaluation of three, four, and five-step thermochemical copper-chlorine cycles for hydrogen production

Thermochemical water-splitting processes are among the most promising options for producing sustainable and green hydrogen due to being extremely environmentally benign. Being extensively investigated in the literature, the thermochemical copper-chlorine cycle has demonstrated much promise in this regard as one of the most efficient options for thermochemically obtaining hydrogen. Thus, this study focuses on investigating the exergoeconomic performances of the different variants of the copper-chlorine cycle including the three-, four-, and five-step versions. All cycles are modeled and simulated in Aspen-plus software by considering a recovery of thermal energy from industrial waste flue gases in addition to internal heat recovery. Moreover, a hydrogen production capacity of 668 kg/h is considered for all cycles. The Specific Exergy Costing methodology is employed to study the exergoeconomic performance of each cycle. All cycles are initially examined in terms of the cost rates of energy transfer and hourly levelized cost rates for each step. The cycle variants are further examined through a comparative assessment of several performance parameters including hydrogen cost rates, overall cost rates of energy transfer, and overall hourly levelized cost rates. According to the performed analyses, the three-step variant of the cycle that constitutes a high-temperature electrolysis process produces hydrogen at the lowest cost rate (0.83 $/kg) while the four-step cycle produces hydrogen at the highest cost rate (1.82 $/kg). Furthermore, the hydrolysis step is found to have the highest hourly levelized cost rates for all variants of the cycle. Several factors that impact the hydrogen cost rate are also examined comprehensively. In addition, the extent to which the hydrogen cost rate is sensitive to those factors is discussed.

Enhanced photocatalytic performance of PS/F-PANI/PNT films for visible-light-induced hydrogen production

This study aims to develop polystyrene/polyaniline/Pt/N-TiO2 (PS/PANI/PNT) photocatalytic films for hydrogen production under simulated sunlight to improve the efficiency of photocatalyst recycling. The effects of the molar ratio of aniline monomer (AN) to oxidizing reagent (ammonium peroxydisulfate, APS) and the weight ratio of AN to PNT on the conductivity of synthesized nanofiber PANI (F-PANI) materials were investigated. PS/PANI/PNT with F-PANI/PNT were synthesized for photocatalytic hydrogen production. An AN/APS molar ratio of 1:2 in F-PANI/PNT was suitable for AN oxidation. The conductive pathway of PANI chains was enhanced by PNT addition at a AN/PNT weight ratio of 1:0.25, which was favorable for enhancing conductivity, facilitating the faster migration of electron–hole pairs to the photocatalyst surface to improve the hydrogen production rate. The F-PANI/PNT photocatalyst effectively separates its electron–hole pairs and has strong electron reduction and hole oxidation abilities, which is suitable for improving the photocatalytic hydrogen production capacity. The contact angle of PS/F-PANI/PNT-2–0.25 was lower than that of PS/PNT, indicating that the hydrophilicity and active sites of PS/F-PANI/PNT-2–0.25 increased. The optimal photocatalytic hydrogen production of F-PS/PANI/PNT (28,580 μmol h-1 g-1) was reached when the polymerization temperature, AN/APS molar ratio, and AN/PNT weight ratio were 5 °C, 1:2, and 1:0.25, respectively. The PS/F-PANI/PNT film showed excellent recyclability, with comparable photocatalytic activity even after five cycle repetition tests. This approach provides a promising alternative to traditional photocatalytic systems and contribute to a more efficient photocatalyst recycling process.

Effect of the vacancy close to heat exchange wall on the heat transfer performance of the solid particles steam generator using waste heat in a methanol steam reforming hydrogen production system

With the massive consumption of fossil fuels and it resulted in significant carbon emissions, it is urgent to find an alternative clean energy source. Hydrogen has been regarded as one of the most promising energy candidates for the next generation. It is a great approach that methane steam reforming for hydrogen production by rational utilization of industrial waste heat, which significantly minimizes carbon emissions and develops methanol steam reforming technology. A solid particle steam generator based on the primary heat exchange method has been proposed, which can provide the heat and steam in the methanol steam reforming hydrogen production system. The quasi-two-dimensional packing heat transfer model of solid particles steam generator was set up. The effect of distance change between the vacancy and the cold wall and distance change between vacancies on heat transfer performance of the steam generator and hydrogen production capacity were studied. As the distance between the vacancy and the wall increases, the heat transfer performance of the steam generator gradually deteriorates, so the steam production of the steam generator decreases, and the system's hydrogen production capacity is reduced, the maximum of the heat flux and the minimum of the apparent thermal resistance are 34.67 kW/m2 and 12.02 K/W, respectively. As the distance between vacancies increases, the heat transfer performance of the steam generator is gradually optimized slightly. To maintain the hydrogen production capacity, vacancies should be avoided to appear 2 layers of particles away from the heat exchange wall in the particles steam generator. From the results of the study, the farther the distance between vacancies, the better the steam production and hydrogen production capacity.