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Solar-driven water splitting by inorganic semiconductor photocatalysts is considered a promising method to produce hydrogen fuel. Loading inorganic semiconductor on cellulose fiber to construct photocatalytic paper contributes to the dispersion and recycling of photocatalyst. In addition, the photocatalytic paper floating on water can build a solid–gas biphase photocatalytic interface (photothermal-generated steam/photocatalytic paper/hydrogen), replacing the traditional liquid–solid–gas triphase photocatalytic interface (liquid water/photocatalyst/hydrogen) for improving photocatalytic kinetics. Here, we design and synthesize a photocatalytic composite paper with zinc sulfide (ZnS) anchored onto cellulose fibers (CF) with the help of polydopamine (PDA). PDA achieves high load and uniform distribution of ZnS on cellulose fibers, and forms the ZnS/PDA heterojunction to increase photogenerated charge separation efficiency and photocatalytic stability. Solid–gas biphase photocatalytic interface constructed by the CF/PDA/ZnS composite paper minimizes the interface barriers of hydrogen transport and water molecular adsorption for improving hydrogen evolution rate. The CF/PDA/ZnS composite paper shows a high hydrogen production rate up to 18706.8 μmol h−1 g−1. Stable loading of ZnS/PDA heterojunction in composite paper contributes to the photocatalytic stability. In the third photocatalytic cycle, the hydrogen evolution rate of CF/PDA/ZnS composite paper remains 96.4%. This work inspires that anchoring of inorganic semiconductor on cellulose fibers with the help of PDA can be a promising strategy for designing efficient photocatalytic paper for solar hydrogen production. [ABSTRACT FROM AUTHOR]

Biomass-based hydrogen production is an innovative approach for realizing carbon-neutral energy solutions. Despite their promise, both structures differ in terms of the biomass energy domain, which is at the entry point of the technology, and the hydrogen energy domain, which is at the exit point of the technology. In this study, we conducted structural and predictive analyses via cross-domain bibliometric analysis to clarify the differences in the structures and perspectives of researchers across domains and to suggest ways to strengthen collaboration to promote innovation. Our study revealed that the hydrogen energy domain has a balanced impact on realizing a hydrogen society using biomass-based hydrogen production technology, while the biomass energy domain has a strong interest in the process of processing biomass. The results reveal that different communities have different ideas about research, resulting in a divide in the areas to be achieved. This comparative analysis reveals the importance of synergistic progress through interdisciplinary efforts. By filling these gaps, our findings can lead to the development of a roadmap for future research and policy development in renewable energy and highlight the importance of a unified approach to sustainable hydrogen production. The contribution of this study is to provide evidence for the importance of cross-disciplinary cooperation for R&D directors and policy makers. [ABSTRACT FROM AUTHOR]

The main objective of this study was to develop a system for the production of "renewable" hydrogen. Paper sludge is a solid industrial waste yielding mainly cellulose, which can be used, after hydrolysis, as a feedstock in anaerobic fermentation by (hyper)thermophilic organisms, such as Thermotoga elfii and Caldicellulosiruptor saccharolyticus. Tests on different medium compositions showed that both bacteria were able to produce hydrogen from paper sludge hydrolysate, but the amount of produced hydrogen and the requirement for other components differed. Hydrogen production by T. elfii strongly depended on the presence of yeast extract and salts. By contrast, C. saccharolyticus was less dependent on medium components but seemed to be inhibited by a component present in the sludge hydrolysate. Utilization of xylose was preferred over glucose by C. saccharolyticus. [ABSTRACT FROM AUTHOR]

The effect of the crystalline phase of TiO2(anatase, rutile and brookite) on its photocatalytic activity in hydrogen production from methanol–water vapours has been investigated by testing a series of both home-made and commercial TiO2photocatalysts, either bare or surface-modified by deposition of a fixed amount, i.e.1 wt%, of platinum as co-catalyst. For all of the TiO2samples the rate of hydrogen production increased by one order of magnitude upon Pt deposition, because of the ability of Pt to enhance the separation of photoproduced electron–hole pairs. Under irradiation in the 350–450 nm wavelength range, brookite and anatase showed similar photoactivities, both superior to that of rutile. By contrast, rutile, possessing a narrower band gap, was active also under visible light (λ> 400 nm), whereas no hydrogen evolution was observed with anatase and brookite under such conditions. Surface area proved to be a key parameter, strongly influencing photoactivity. However, as the particle size became ultra-small, the semiconductor absorption edge was blue-shifted because of size quantisation effects, with a consequent decrease in hydrogen production rate due to the smaller portion of incident photons absorbed by the photocatalyst. [ABSTRACT FROM AUTHOR]

Titanium dioxide was modified with Pt–polypyrrole nanocomposites through the in situsimultaneous reduction of Pt(iv) and the oxidative polymerization of pyrrole monomers at ambient temperature. The modified powders were characterized using X-ray photoelectron spectroscopy (XPS), dark-field scanning transmission electron microscopy (DF-STEM), infrared spectroscopy (IR) and by the determination of the BET surface area by nitrogen adsorption. Photocatalytic hydrogen production tests were performed employing 75 ml aqueous solution containing 2250 μmol methanol as the sacrificial electron donor. The obtained results show that 0.5 and 1.0 wt% Pt and polypyrrole, respectively, are the optimum ratios for high photocatalytic H2production rates. The amount of H2evolved during 5 h of UV-vis illumination of the suspension of Pt–polypyrrole modified TiO2powder is three times higher than that obtained with Pt-loaded TiO2prepared by a photochemical deposition method. The photonic efficiencies of the H2production employing 75 ml aqueous solution containing 370 mmol methanol were calculated to be 10.6 ± 0.5 and 4.5 ± 0.2% for TiO2modified with Pt–polypyrrole nanocomposites and for Pt-loaded TiO2prepared by a photochemical deposition method, respectively. A synergistic effect between Pt nanoparticles and polypyrrole leading to a better separation of the charge carriers is proposed to explain the enhanced reactivity of the newly synthesized photocatalyst. [ABSTRACT FROM AUTHOR]

Titania nanocrystalline films have been deposited on glass slides and loaded with Pt nanoparticles by adsorption from aqueous solutions of sodium tetrachloroplatinate followed by UVA radiation or heat treatment. These metal/semiconductor combined photocatalysts have been used for photooxidation of aqueous ethanol and production of hydrogen. The efficiency of the photocatalytic process was associated with the metal load on the titania films and the size of the metal nanoparticles. Characterization of the combined photocatalyst has been made by X-ray photoelectron spectroscopy and transmission electron microscopy. [ABSTRACT FROM AUTHOR]

SOEC (Solid Oxide Electrolysis Cell) require high temperature steam, but generating steam with electricity is very energy intensive. Concentrated solar power can be a good substitute for electricity to generate high temperature steam. In this paper, the thermal performance of a solar steam generator is researched. The steam generator improves the heat transfer capacity by installing porous ceramic material inside and using spray cooling technique. Due to the limited heat transfer capacity of previous steam generators, other types of steam generators can only produce steam with a temperature below 700°C. The steam generator in this paper has a high thermal efficiency depending on the nozzle characteristics. Therefore, the steam generator has obvious advantages in terms of generating high-temperature steam. The experimental results show that the instantaneous thermal efficiency of the steam generator with a new nozzle can reach a maximum of 58% when the solar irradiation power is 2.26 kW and the inlet water flow rate is 1.23 kg/h. At this time, the steam generator can produce high temperature water vapour at a maximum temperature of 715.4°C. The optimized solar steam generator was also coupled with the SOEC system, and hydrogen production was successfully achieved by experimental means. The solar SOEC system has great potential for hydrogen production. [ABSTRACT FROM AUTHOR]

Supercritical water gasification is a clean technology for biomass conversion and utilization. In supercritical water gasification systems, H2O is often used as the transport medium. Decreases in the reaction temperature at the gasification area and in the heating rate of biomass may limit the gasification rate and efficiency. In this paper, CO2 is used as the transport medium due to its relatively low critical point and specific heat capacity. Moreover, a corn stalk gasification system with different transport media is established in this paper, and the influences of various operating parameters, such as temperature, pressure and feedstock concentration, are investigated. The results show that the gas yield in the CO2-transport system decreases by no more than 5 wt %. In addition, thermodynamic analysis reveals that a system with CO2 as transport medium consumes approximately 25% less electricity than a system with H2O as the transport medium. In addition, the reaction heat absorption decreases. The results show the superiority of CO2 to H2O as a transport medium. [ABSTRACT FROM AUTHOR]

Highly dispersed Cobalt doped ZnS nanostructures were successfully fabricated on the surfaces of graphene sheets via a simple hydrothermal method. X-ray diffraction (XRD), X-ray photocurrent spectroscopy (XPS), Raman spectroscopy (RS), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) were utilized to analyze the structural characteristics of the cobalt doped ZnS decorated with graphene Co x Zn 1 - x S rGO nanostructures (NSs). UV-visible optical absorption (UV-vis) studies were conducted to investigate their optical properties. In laboratory studies utilizing water and visible light, the photocatalytic activity of Co x Zn 1 - x S rGO NSs at (x = 0, 1, 2, 4 and 6 atm.%) were evaluated. Graphite Oxide (GO) was successfully transformed into sheets of graphene and Co x Zn 1 - x S rGO NSs possessed a crystalline structure according to the findings of XRD, RS and FTIR analysis. SEM investigation showed graphene sheets enhanced with ZnS NSs possessed cuboidal, spheroidal form of structure and displayed a paper like appearance. UV-vis confirmed a noticeable rapid increase in transmittance along the UV wavelength area and confirmed a highly transparent NSs in the wavelength range of (180-800 nm). Calculations using density functional theory (DFT) revealed that the Co NSs have more negative conduction bands than ZnS, allowing for effective electron transfer from cobalt to ZnS and exhibiting a band gap decrease as Co content increased. The Co 0.04 Zn 0.96 S rGO NSs sample had the highest photocatalytic activity, measured at 7648.9 μ mol h - 1 . A combination of improved dispersion properties, greater surface area, increased absorption and enhanced transfer of photogenerated electrons, Co x Zn 1 - x S rGO NSs increased the photocatalytic hydrogen generation activity. [ABSTRACT FROM AUTHOR]

The increasing demand for energy, depletion of traditional energy sources, and environmental concerns have generated an energy crisis in recent years. To address this challenge, innovative and low-cost solutions have been sought, such as the use of 3D printing for decentralized hydrogen production. In this paper, we present the production of conductive filaments prepared from polylactic acid (PLA) and Carbon Black (CB), which were used for the 3D printing of electrodes. The produced materials were characterized by scanning electron microscopy, thermal analysis, and electrochemical techniques. The 3D-printed electrodes were used as substrates for CoPi electrodeposition to evaluate their performance in hydrogen production. The 3D-printed electrodes, made from filaments prepared in the laboratory, demonstrated superior electrochemical performance and hydrogen production compared to electrodes printed compared with commercial filament. The PLA@CB72R and CoPi#PLA@CB72R electrodes showed better hydrogen production performance, 10.08 and 10.20 μmol min−1, respectively. This study provides a perspective for the manufacture of filaments and 3D-printed electrodes for energy conversion applications, such as hydrogen production. [ABSTRACT FROM AUTHOR]

Green hydrogen and synthetic fuels are increasingly recognized as a key strategic element for the progress of the global energy transition. The Middle East and North Africa (MENA) region, with its large wind and solar potential, is well positioned to generate renewable energy at low cost for the production of green hydrogen and synthetic fuels, and is therefore considered as a potential future producer and exporter. Yet, while solar and wind energy potentials are essential, other factors are expected to play an equally important role for the development of green hydrogen and synthetic fuels (export) sectors. This includes, in particular, adequate industrial capacities and infrastructures. These preconditions vary from country to country, and while they have been often mentioned in the discussion on green hydrogen exports, they have only been examined to a limited extent. This paper employs a case study approach to assess the existing infrastructural and industrial conditions in Jordan, Morocco, and Oman for the development of a green hydrogen and downstream synthetic fuel (export) sector. [ABSTRACT FROM AUTHOR]

Hydrogen energy, as clean and efficient energy, is considered significant support for the construction of a sustainable society in the face of global climate change and the looming energy revolution. Hydrogen is one of the most important chemical substances on earth and can be obtained through various techniques using renewable and nonrenewable energy sources. However, the necessity for a gradual transition to renewable energy sources significantly hampers efforts to identify and implement green hydrogen production paths. Therefore, this paper's objective is to provide a technological review of the systems of hydrogen production from solar and wind energy utilizing several types of water electrolyzers. The current paper starts with a short brief about the different production techniques. A detailed comparison between water electrolyzer types and a complete illustration of hydrogen production techniques using solar and wind are presented with examples, after which an economic assessment of green hydrogen production by comparing the costs of the discussed renewable sources with other production methods. Finally, the challenges that face the mentioned production methods are illuminated in the current review. [ABSTRACT FROM AUTHOR]

This paper presents the preparation and performance evaluation of two closed-loop nickel-based catalysts. The (hydro)oxide coatings of nickel-molybdenum and nickel-iron were electrodeposited onto industrial nickel meshes, which were subsequently used as the cathode and anode (NiMo@NM and NiFe@NM) in alkaline water electrolysis. Both catalysts formed a fully closed-loop configuration, surrounding each nickel wire on the nickel mesh, thereby enhancing the bonding strength with the substrate. The NiMo@NM||NiFe@NM assembly achieved a current density of 200 mA cm−2 at a cell voltage of only 1.91 V and room temperature, maintaining this level of performance for over 280 h. A single-stack flow cell was used to examine the changes in cell voltage in relation to temperature, current density, and electrolyte flow rate and concentration. The specific energy consumption for hydrogen production can be reduced to 4.1 kWh Nm−3 (H2) under near-industrial conditions (70 °C, 6 M KOH, 400 mA cm−2). We hope that this study can help bridge the gap between catalyst studies and practical industrial applications. [ABSTRACT FROM AUTHOR]

Catalytic hydrolysis of ammonia borane (AB) can be applied as an on-demand hydrogen production system. Low-cost and highly active catalysts towards AB hydrolysis are highly desirable for the industrial application of this technology. In this paper, we have reported the synthesis of Cu3P-Co2P nanoplatelets by a simple method and the formation process of the final products. It is revealed that Cu2O–Co(OH)2 composite nanoplatelets are obtained after hydrothermal reaction, which are transformed into Cu3P-Co2P nanoplatelets during the phosphorization process. In AB hydrolysis, the Cu3P-Co2P nanoplatelets exhibit high catalytic activity with the hydrogen generation rate of 4.03 LH2 gcat.−1 min−1, which is much higher than those for many noble-metal-free catalysts in the documents. It is discovered that AB hydrolysis follows the pseudo-first-order kinetics with respect to the catalyst dosage and pseudo-zero-order kinetics with respect to the AB amount. In view of the cheapness and high performance, the Cu3P-Co2P nanoplatelets can be a promising catalyst candidate to AB hydrolysis for hydrogen production. [ABSTRACT FROM AUTHOR]

The production of green hydrogen and its scale-up require the enginering and installation of new electrolysis plants. Modular electrolysis plants ease the scale-up as they allow to add further modules with growing demand. While many engineering methods focus on the detailed planning of the plants and their automation systems, the early engineering phases are scarcely considered, supported or formalized. However, especially these phases are crucial in the current scale-up of modular electrolysis plants. In this paper, an intention-based engineering approach for the early engineering phases Requirements Engineering and Conceptual Engineering for modular electrolysis plants is presented and evaluated based on three different use cases. The approach is based on Goal-oriented Requirements Engineering from Software Engineering and relies on an early, systematic as well as formalized description and analysis of intentions of different engineering disciplines. [ABSTRACT FROM AUTHOR]

Production of hydrogen, one of the most promising alternative clean fuels, through catalytic conversion from fossil fuel is the most technically and economically feasible technology. Catalytic conversion of natural gas into hydrogen and carbon is thermodynamically favorable under atmospheric conditions. However, using noble metals as a catalyst is costly for hydrogen production, thus mandating non-noble metal-based catalysts such as Ni, Co, and Cu-based alloys. This paper reviews the various hydrogen production methods from fossil fuels through pyrolysis, partial oxidation, autothermal, and steam reforming, emphasizing the catalytic production of hydrogen via steam reforming of methane. The multicomponent catalysts composed of several nonnoble materials have been summarized. Of the Ni, Co, and Cu-based catalysts investigated in the literature, Ni/Al2O3 catalyst is the most economical and performs best because it suppresses the coke formation on the catalyst. To avoid carbon emission, this method of hydrogen production from methane should be integrated with carbon capture, utilization, and storage (CCUS). Carbon capture can be accomplished by absorption, adsorption, and membrane separation processes. The remaining challenges, prospects, and future research and development directions are described. [ABSTRACT FROM AUTHOR]

In recent years, there has been a significant deal of interest in the photo-fermentation-based synthesis of biological hydrogen due to its unique advantages, such as high hydrogen yield and the use of renewable raw materials as substrates. This paper assesses biological hydrogen production by photo-fermentation using the purple non-sulfur bacteria Rhodobacter capsulatus and Rhodospirillum rubrum cultivated in Rhodobacter capsulatus V minimal (RCV) medium. Lactose was used as a carbon source at a starting concentration of 10 g/L. An investigation of the use Rhodobacter capsulatus and Rhodospirillum rubrum strains in mixed culture confirmed the viability of the use of a co-culture system in detriment of mono-culture systems. On average, co-cultured hydrogen responses resulted in 1.43- and 1.50-fold increases in hydrogen productivity and yield, respectively, between the two species. The experiments were also conducted in a 1.5-L stirred tank reactor using repeated batch cycles, with or without medium renewal. The medium renewal allowed for the removal of organic acids produced by cellular metabolism and ensured stable and long-term hydrogen production, reaching peak productivity 278.05 mmol H2/L/day and maximum yield 19.67 mol H2/mol lactose (82% of the theoretical yield). For comparative purposes, a subsequent assay was carried out in the same initial conditions without medium renewal. An accumulation of organic acids resulted in lower peak productivity of 104.47 mmol H2/L/day and lower peak hydrogen yield of 11.71 mol H2/mol lactose confirming viability of medium renewal strategy to improve hydrogen production in photo-fermentation. [ABSTRACT FROM AUTHOR]

Green hydrogen is a buzzword in today's renewable energy applications research domain. This paper analyzes the performance of the photovoltaic (PV) and thermoelectric generator (TEG) systems for the same reason. The prototype system includes PV, TEG, a heat sink, and a Hofmann Voltameter. The output of the PV–TEG is initially connected to a Hofmann Voltmeter to conduct electrolysis of groundwater and seawater. Further, a heat sink is pasted on each TEG using a thermally conductive adhesive. Then again, PV–TEG/heat sink output is connected to the Voltameter for electrolysis on the same water source samples. Finally, the comparative exploration is done to give insights into PV–TEG applications for hydrogen production. The explorative study shows a DC voltage gain of up to 1.77 times concerning TEG alone. Further, at 849 W/m2 of solar irradiance, it is observed that hydrogen production varies from 0.1552 to 0.1639 bar/sec in the case of groundwater and that of seawater goes from 0.1362 to 0.1413 bar/sec when PV–TEG with a heat sink is connected to Voltameter. [ABSTRACT FROM AUTHOR]

In a hydrogen economy, the primary energy source for industry, transportation, and power production is hydrogen gas. Green hydrogen can be generated and utilized in an environmentally friendly and sustainable manner; it seeks to displace fossil fuels. Finding a clean alternative energy source is becoming more crucial due to the depletion of fossil fuels and the major environmental pollution issues they bring when utilized extensively. The paper's objective is to analyze the factors affecting the economy of green hydrogen production pathways for sustainable development to decarbonize the world and the associated challenges faced in terms of technological, social, infrastructure, and people's perceptions while adopting green hydrogen. To achieve this, the research looked at a variety of areas relevant to green hydrogen, such as production techniques, industry applications, benefits for society and the environment, and challenges that need to be overcome before the technology is widely used. The most recent methods of producing hydrogen from fossil fuels, such as steam methane, partial oxidation, autothermal, and plasma reforming, as well as renewable energy sources including biomass and thermochemical reactions and water splitting. Grey hydrogen is now the least expensive type of hydrogen, but, in the future, green hydrogen's levelized cost of hydrogen (LCOH) is expected to be less than $2 per kilogram of hydrogen. [ABSTRACT FROM AUTHOR]

A good bifunctional electrocatalyst can effectively drive water splitting to produce hydrogen gas. In this paper, NiMoO4an nanomaterial was prepared and combined with black phosphorus (BP) in a one-step method. Used as a bifunctional electrocatalyst, the composite demonstrated outstanding electrochemical performance with 162.7 mV and 137.6 mV achieving current densities of 20 mA cm−2 and 10 mA cm−2 for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), respectively. For overall water splitting, the potential was just 1.55 V to achieve 10 mA cm−2, and, especially, the value only rises by0.05 V after 2000 cycles of CV. Here, the one-step synthesis method favors the dispersion of NiMoO4 nanomaterial on the BP surfaces, and facilitates a combination between the nickel molybdate and the BP. Also, the excellent performance of the samples should benefit from the synergistic action between the components. [ABSTRACT FROM AUTHOR]

Lithium–sulfur batteries as one of the most promising technologies for energy storage applications have been attracting increasing attentions. A crucial challenge for the commercialization of lithium–sulfur batteries is the poor stability of lithium sulfide against moisture, which may lead to the release of toxic hydrogen sulfide gas. However, the risk of hydrogen sulfide releasing from lithium–sulfur batteries under the limiting conditions is still unclear. In this paper, we herein investigate the mechanism of hydrogen sulfide releasing in lithium–sulfur batteries, and evaluate the effect of battery discharging on the generation of hydrogen sulfide. The production of sulfion and hydrogen sulfide is qualitatively/qualitatively studied. According to above results, the behavior of hydrogen sulfide formation in the batteries is elucidated based on thermodynamic simulation. Furthermore, the effect of discharging of lithium–sulfur batteries on the hydrogen sulfide releasing is qualitatively calculated. These results show that the hydrogen sulfide is indeed produced from the discharging products of lithium–sulfur battery under the acid condition, the findings can also provide some guidelines or suggestions for the practical applications of lithium–sulfur battery. [ABSTRACT FROM AUTHOR]

Urea is mainly derived from animal urine and urea industry. The discharge of wastewater rich in urea causes serious harm to the environment and human health. Urea electrooxidation technology is an important means to remove urea pollutants, which has the dual significance of environmental protection and clean energy production. However, the kinetics of urea oxidation is slow, so it is urgent to develop efficient catalysts for urea electrooxidation. In recent years, nickel-based materials as effective catalysts for urea electrooxidation have been favored by researchers because of their low cost, high activity, and high stability. Suitable support can significantly improve the catalytic performance of electrocatalyst. In this paper, the research progress of supported nickel-based catalysts in the field of urea electrooxidation was reviewed, and the applications of supported nickel-based catalysts in urea electrolysis hydrogen production, fuel cells, and urea sensors were reviewed in detail. The development prospect, challenges, and practical applications of supported nickel-based catalysts are discussed. [ABSTRACT FROM AUTHOR]

Hydrogen energy, a new type of clean and efficient energy, has assumed precedence in decarbonizing and building a sustainable carbon-neutral economy. Recently, hydrogen production from water splitting has seen considerable advancements owing to its advantages such as zero carbon emissions, safety, and high product purity. To overcome the large energy barrier and high cost of water splitting, numerous efficient electrocatalysts have been designed and reported. However, various difficulties in promoting the industrialization of electrocatalytic water splitting remain. Further, as high-performance electrocatalysts that satisfy industrial requirements are urgently needed, a better understanding of water-splitting systems is required. In this paper, the latest progress in water electrolysis is reviewed, and experimental evidence from in situ/operando spectroscopic surveys and computational analyses is summarized to present a mechanistic understanding of hydrogen and oxygen evolution reactions. Furthermore, some promising strategies, including alloying, morphological engineering, interface construction, defect engineering, and strain engineering for designing and synthesizing electrocatalysts are highlighted. We believe that this review will provide a knowledge-guided design in fundamental science and further inspire technical engineering developments for constructing efficient electrocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

Numerous catalysts have been studied and developed to catalyze the decomposition of methane and in this paper, an iron slab is selected as the catalyst to obtain stable Fe3C and C2 during the decomposition of methane. We combine ReaxFF MD simulations and laboratory work to investigate methane decomposition and carburization of carbon atoms. The analysis of XRD and TEM confirms the Fe3C formed after the reaction and demonstrates its microscopic morphology. Simulations reveal that the iron slab accelerates the primary decomposition of CH4 in the meantime promotes the synthesis of hydrogen molecules and the whole carburizing reaction mechanism has been characterized by the formation of Fe3C and diffusion of C atoms which has been described with carburizing depth. Finally, the influence of methane concentration is explored and the result shows that an appropriate enhancement accelerates the carburizing reaction while the excessive increase will inhibit it. [ABSTRACT FROM AUTHOR]

The paper defines the conditions for the synthesis of hydrogen sulfide adsorbent based on zinc oxide from basic zinc carbonate in order to produce strong, porous and non-dusting pellets of a sulfur-adsorbing mass. It is proposed to prepare the adsorbent by mixing nanocrystalline and coarsely dispersed ZnO. It was proven that the introduction of solutions of carboxymethyl cellulose and hydroxypropyl cellulose into the extraction paste makes it possible to reduce the fraction of plastic deformations in the ZnO suspension from 79.8 to 56.1%. In this paper the rheological properties of zinc oxide are investigated. According to the Maxwell–Shvedov and Kelvin model, all the studied systems belong to the fourth structural-mechanical type. Tests of a sulfur adsorbent based on zinc oxide suspensions showed that in the temperature range of 300–400°C in the reaction gas mixture H2S 10%, N2 90%, there are completely no sulfur compounds at the outlet. It has been established that the formability of the ZnO-based paste is possible at an optimum moisture content of 33.4%. [ABSTRACT FROM AUTHOR]

The Japanese government has announced a commitment to net-zero greenhouse gas emissions by 2050. It envisages an important role for hydrogen in the nation's future energy economy. This paper explores the possibility that a significant source for this hydrogen could be produced by electrolysis fueled by power generated from offshore wind in China. Hydrogen could be delivered to Japan either as liquid, or bound to a chemical carrier such as toluene, or as a component of ammonia. The paper presents an analysis of factors determining the ultimate cost for this hydrogen, including expenses for production, storage, conversion, transport, and treatment at the destination. It concludes that the Chinese source could be delivered at a volume and cost consistent with Japan's idealized future projections. Hydrogen is regarded as important to Japan's clean energy transition. Here the authors consider the production of hydrogen by electrolysis fueled by offshore wind power in China, and the potential for delivery to Japan as part of Japan's transition. [ABSTRACT FROM AUTHOR]

Targeting the net-zero emission (NZE) by 2050, the hydrogen industry is drastically developing in recent years. However, the technologies of hydrogen upstream production, midstream transportation and storage, and downstream utilization are facing obstacles. In this paper, the development of hydrogen industry from the production, transportation and storage, and sustainable economic development perspectives were reviewed. The current challenges and future outlooks were summarized consequently. In the upstream, blue hydrogen is dominating the current hydrogen supply, and an implementation of carbon capture and sequestration (CCS) can raise its cost by 30%. To achieve an economic feasibility, green hydrogen needs to reduce its cost by 75% to approximately 2 $/kg at the large scale. The research progress in the midterm sector is still in a preliminary stage, where experimental and theoretical investigations need to be conducted in addressing the impact of embrittlement, contamination, and flammability so that they could provide a solid support for material selection and large-scale feasibility studies. In the downstream utilization, blue hydrogen will be used in producing value-added chemicals in the short-term. Over the long-term, green hydrogen will dominate the market owing to its high energy intensity and zero carbon intensity which provides a promising option for energy storage. Technologies in the hydrogen industry require a comprehensive understanding of their economic and environmental benefits over the whole life cycle in supporting operators and policymakers. [ABSTRACT FROM AUTHOR]

Tapping the full potential of clean, renewable energy resources to effectively meet the steadily increasing energy demand is the critical need of the hour and an important proactive step towards achieving sustainability. India's solar energy consumption has witnessed a nearly twofold increase from 6.76 GW in 2015–16 to 12.28 in 2016–17. Since India enjoys the advantage of high solar insolation, increasing the efficiency of solar power systems can tremendously boost clean energy generation. The escalating energy crisis currently faced by India has compelled scientists and researchers to focus on identifying novel economical and efficient technologies for large-scale energy production. Direct utilization of solar energy for fuel conversion has attained greater importance. In this context, generation of hydrogen from industrial wastewater by using solar energy offers significant economic as well as environmental benefits. This investigative review paper focuses on the importance of the solar photocatalytic process to recover the clean energy H2 from sulphide containing industrial wastewater. [ABSTRACT FROM AUTHOR]

In this paper, a new integrated system is proposed consisting of four subsystems, including a Cu–Cl cycle, a carbon capture cycle (sodium-based sorbent), an ammonia production unit, and a methanation unit. Carbon capturing cycle with sodium-based sorbent could adsorb 1.5 times more than other sorbents such as amine-based sorbent. Moreover, Cu–Cl cycle is one of the promising cycles in terms of economic and low temperature. Therefore, integrating these two cycles with ammonia and methane production unit is the novelty for this paper. Also, Aspen plus software was used to simulate the developed system to evaluate the process of the system. Moreover, sensitivity analysis and mass/energy balance are performed for the developed systems through the simulation. The energy required to capture carbon dioxide was found to be 6.313 MW per kg of CO2, and the overall efficiency of the system is equal to 19.6%. [ABSTRACT FROM AUTHOR]

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Hydrogen energy has been widely accepted as renewable and clean energy source. However, safety problems exist in the process of hydrogen energy transportation and storage. On-site hydrogen production has great potential to solve safety problems, and dimethyl ether (DME) is an excellent hydrogen carrier. There are four ways for hydrogen production from DME, and they are DME steam reforming, partial oxidation of DME, autothermal reforming of DME, and plasma reforming of DME, respectively. Catalysts are essential for the first three reactions and the last one could achieve the activation of DME just through election catalysis. To the best of our knowledge, a review of hydrogen production from DME has not been reported, which should be discussed systematically. In this review, the advantages and disadvantages of different DME reforming processes are discussed, and the progress of catalysts for the reforming processes as well as the effects of catalysts in the reactions are summarized. This paper also provides the rational design of highly efficient catalysts on DME in the future. [ABSTRACT FROM AUTHOR]

The increasing demand for efficient sensing devices with facile low-cost fabrication has attracted a lot of scientific research effort in the recent years. In particular, the scientific community aims to develop new candidate materials suitable for energy-related devices, such as sensors and photovoltaics or clean energy applications such as hydrogen production. One of the most prominent methods to improve materials functionality and performance is doping key device component(s). This paper aims to examine in detail, both from a theoretical and an experimental point of view, the effect of halogen doping on the properties of tin dioxide (SnO2) and provide a deeper understanding on the atomic scale mechanisms with respect to their potential applications in sensors. Density Functional Theory (DFT) calculations are used to examine the defect processes, the electronic structure and the thermodynamical properties of halogen-doped SnO2. Calculations show that halogen doping reduces the oxide bandgap by creating gap states which agree well with our experimental data. The crystallinity and morphology of the samples is also altered. The synergy of these effects results in a significant improvement of the gas-sensing response. This work demonstrates for the first time a complete theoretical and experimental characterization of halogen-doped SnO2 and investigates the possible responsible mechanisms. Our results illustrate that halogen doping is a low-cost method that significantly enhances the room temperature response of SnO2. [ABSTRACT FROM AUTHOR]

This paper is a contribution to the development of microwave plasma-based technology aimed at efficient hydrogen (H2) production from a so-called synthetic biogas, considered a mixture of methane (CH4) and carbon dioxide (CO2), which can contain up to 70% CH4. In this work, we tested the performance of a waveguide-supplied metal cylinder-based microwave plasma source (MPS) operating at 915 MHz at atmospheric pressure as a tool for the efficient production of H2 in the steam reforming of the synthetic biogas. The test showed that the steam reforming of the synthetic biogas could be carried out under a wide range of working parameters without soot formation and extinction of the microwave discharge. We found that there is a minimal H2Osteam consumption rate for a given CH4 input volume content, which ensures stable operation of the MPS (no soot). The experiments did not show that increasing the amount of H2Osteam rate above the minimal value for a given CH4 input volume content results in an increase in the H2 production rate, energy yield, CH4 conversion degree, and H2 output concentration. To describe the MPS performance, which also takes into account a factor of the utilization of the CH4 feedstock, we introduced a new parameter, called an energy–CH4 feedstock consumption yield. The best results in terms of the H2 production rate, the energy yield, and the CH4 conversion degree were 239 g[H2]/h 36.8 g[H2]/kWh, and 74.3%, respectively. This shows that the application of the steam reforming, instead of the dry reforming, resulted in a 1.5-fold increase of the H2 production rate and the corresponding energy yield. [ABSTRACT FROM AUTHOR]

The anode activity can to a great degree limit the cathodic hydrogen evolution efficiency in an electrolyte cell. Thus, cost-efficient electrocatalysts with good water oxidation performance and stability are highly desired in widespread implementation of the hydrogen production from water splitting. This paper proposes a facile corrosion-reconstruction strategy to transform Fe surface into a Fe-Co hydroxide layer to improve the oxygen evolution activity. The as-prepared catalyst was measured to have an over-potentential as low as 320 mV at 100 mA·cm−2, and its stability even exceeded 600 h. Surface and Raman spectroscopy analyses indicated that the catalyst experienced chemical changes from hydroxides to oxyhydroxides and Co2+ to Co3+ during oxygen evolution reaction (OER). The corrosion-reconstruction is not only an economical method to synthesize a highly efficient, stable and durable Fe-based catalysts, it also converses the detrimental corrosion into a beneficial catalyst fabrication process. [ABSTRACT FROM AUTHOR]

In this paper, Ti3C2 was completely oxidized at a high temperature (350 °C, 400 °C and 450 °C) to form a composite catalysts: TiO2 nanoparticles with fragmentary carbon supporting, using the ZnCl2 molten salt method. The generated disordered carbon forms an inseparable connection with TiO2 nanoparticles grown in situ on the surface, which reduces the recombination of photocarriers and increases the specific surface area. ZnCl2 plays an important role in delaying the oxidation rate, thus inhibiting the abnormal growth of TiO2 grain and retaining more carbon, which led to a suitable composition of the catalyst, so as to obtain a better hydrogen production performance. ZnCl2 existence might also prevent the collapse of the accordion structure during the calcination process. The hydrogen production activity of C–TiO2 photocatalyst prepared by molten salt method with 3 wt% Pt as cocatalyst is up to 2.3 mmol/g/h, about 5.4 times and 2 times of that of calcination without molten salt and pure P25, respectively. [ABSTRACT FROM AUTHOR]

It was the constant pursuit of researchers to explore catalysts with higher catalytic activity, and the use of co-catalysts to modify the performance of photocatalytic materials had a significant effect on charge separation. In this paper, the non-precious metal NiS-modified ZnCo2O4 composite catalytic material prepared by hydrothermal method had high-efficiency catalytic performance. When the weight ratio of NiS to ZnCo2O4 was 12%, the optimal catalytic activity is 3.57 mmol g−1 h−1, which was more than twice that of ZnCo2O4. The presence of NiS not only improved the specific surface area of the catalyst and its ability to respond to light, but the close interface formed by the combination of the two monomer phases accelerated the transfer and the utilization of the photocharge on ZnCo2O4 to NiS, thereby promoting the separation of electron holes and improving the photocatalytic activity of the catalyst. According to the research results, the mechanism of hydrogen production in the photocatalytic system was revealed. In this paper, NiS was used to modify the bimetallic oxide with cubic appearance, which provided a new strategy for the development of new photocatalysts. [ABSTRACT FROM AUTHOR]

In the recent years, molybdenum disulfide (MoS2) has been widely used in various optical applications. MoS2 has decent optical band gap and can be used as photocatalyst for hydrogen production applications. In this paper, we reported the synthesis of flower-like nickel (Ni)-doped MoS2. The as-prepared Ni@MoS2 has optical band gap of 1.71 eV which was lower than that of the pristine MoS2 (1.90 eV). Thus, Ni@MoS2 was further used as photocatalyst for hydrogen evolution. The effect of different dose (5, 10, 15, 20 and 25 mg) of the photocatalyst (Ni@MoS2) was also examined. The photocatalytic investigations exhibited the generation of good hydrogen production amount (2021.5 µmol g−1) with reasonable hydrogen generation rate of 404.3 µmol g−1 h−1 using 25 mg Ni@MoS2. These findings suggested that doping may significantly improve the photocatalytic hydrogen production. The proposed Ni@MoS2 also presented good stability and reusability for hydrogen production. [ABSTRACT FROM AUTHOR]

The objective of this paper is to gain insights into the synergistic advantage of anaerobic co-fermentation of heat-treated sludge (HS) with food waste (FW) and heat-treated food waste (HFW) for hydrogen production. The results showed that, compared with raw sludge (RS) mixed with FW (RS-FW), the co-substrate of HS mixed with either FW (HS-FW) or HFW (HS-HFW) effectively promoted hydrogen production, with HS-HFW promoted more than HS-FW. The maximum specific hydrogen production (MSHP) and the maximum hydrogen concentration (MHC) of HS-HFW were 40.53 mL H2/g dry weight and 57.22%, respectively, and 1.21- and 1.45-fold as high as those from HS-FW. The corresponding fermentation was ethanol type for HS-HFW and butyric acid type for HS-FW. The net energy production from RS-FW and HS-FW was both negative, but it was positive (2.57 MJ) from 40% HFW addition to HS-HFW. Anaerobic fermentation was more viable for HS-HFW. [ABSTRACT FROM AUTHOR]

Owing to the significant number of hybrid generation systems (HGSs) containing various energy sources, coordination between these sources plays a vital role in preserving frequency stability. In this paper, an adaptive coordination control strategy for renewable energy sources (RESs), an aqua electrolyzer (AE) for hydrogen production, and a fuel cell (FC)-based energy storage system (ESS) is proposed to enhance the frequency stability of an HGS. In the proposed system, the excess energy from RESs is used to power electrolysis via an AE for hydrogen energy storage in FCs. The proposed method is based on a proportional-integral (PI) controller, which is optimally designed using a grey wolf optimization (GWO) algorithm to estimate the surplus energy from RESs (i.e., a proportion of total power generation of RESs: Kn). The studied HGS contains various types of generation systems including a diesel generator, wind turbines, photovoltaic (PV) systems, AE with FCs, and ESSs (e.g., battery and flywheel). The proposed method varies Kn with varying frequency deviation values to obtain the best benefits from RESs, while damping the frequency fluctuations. The proposed method is validated by considering different loading conditions and comparing with other existing studies that consider Kn as a constant value. The simulation results demonstrate that the proposed method, which changes Kn value and subsequently stores the power extracted from the RESs in hydrogen energy storage according to frequency deviation changes, performs better than those that use constant Kn. The statistical analysis for frequency deviation of HGS with the proposed method has the best values and achieves large improvements for minimum, maximum, difference between maximum and minimum, mean, and standard deviation compared to the existing method. [ABSTRACT FROM AUTHOR]

The paper presents a fundamentally new design for a hydrogen generator. Hydrogen is released during the reaction of activated aluminum and water. Bismuth, tin, and calcium oxide were used as the activating additives. The hydrogen generator results in an Al oxidation reaction at a temperature of 100–350°C and a pressure of about 4 atm. An average hydrogen production rate of 30 mL/(s g) was achieved with a hydrogen yield of 95–99% of the theoretically possible value. In continuous generation mode, the average productivity of the hydrogen generator was ~1.5 kW (140 mL H2/s). [ABSTRACT FROM AUTHOR]

Transient electronics that can disappear or degrade via physical disintegration or chemical reaction over a pre-defined operational period provide essential for their applications in implantable bioelectronics due to the complete elimination of the second surgical extraction. However, the dissolution of commonly utilized bioresorbable materials often accompanies hydrogen production, which may cause potential or irreparable harm to the human body. This paper introduces germanium nanomembrane-based bioresorbable electronic sensors, where the chemical dissolution of all utilized materials in biofluidic theoretically have no gaseous products. In particular, the superior electronic transport of germanium enables the demonstrated bioresorbable electronic sensors to successfully distinguish the crosstalk of different physiological signals, such as temperature and strain, suggesting the significant prospect for the construction of dual or multi-parameter biosensors. Systematical studies reveal the gauge factor and temperature coefficient of resistance comparable to otherwise similar devices with gaseous products during their dissolution. [ABSTRACT FROM AUTHOR]

According to the estimates made in this paper, neither hydropower and nuclear power engineering nor, the more so, other renewable power sources are capable in principle to ensure the commercial hydrogen production volumes required for noticeable reduction of the global carbon dioxide emission. Before mastering the thermonuclear synthesis energy, only the conversion of hydrocarbons can be the real source of hydrogen for commercial power generation. Therefore, making these processes more efficient is the best way to reduce the carbon footprint of the power generation. It should also be noted that hydrogen as a power carrier has serious drawbacks, the main of which is the low volumetric energy content. Transportation and storage of hydrogen, compared to natural gas, are considerably more money- and power-consuming. The most feasible way to overcome the yet unsolved problems of hydrogen storage and transportation is to set up decentralized low-tonnage production of hydrogen directly on the consumption sites. Such technologies have been already developed in Russia, and active efforts should be made to implement them. [ABSTRACT FROM AUTHOR]

As an eco-friendly, efficient, and low-cost technique, photoelectrochemical water splitting has attracted growing interest in the production of clean and sustainable hydrogen by the conversion of abundant solar energy. In the photoelectrochemical system, the photoelectrode plays a vital role in absorbing the energy of sunlight to trigger the water splitting process and the overall efficiency depends largely on the integration and design of photoelectrochemical devices. In recent years, the optimization of photoelectrodes and photoelectrochemical devices to achieve highly efficient hydrogen production has been extensively investigated. In this paper, a concise review of recent advances in the modification of nanostructured photoelectrodes and the design of photoelectrochemical devices is presented. Meanwhile, the general principles of structural and morphological factors in altering the photoelectrochemical performance of photoelectrodes are discussed. Furthermore, the performance indicators and first principles to describe the behaviors of charge carriers are analyzed, which will be of profound guiding significance to increasing the overall efficiency of the photoelectrochemical water splitting system. Finally, current challenges and prospects for an in-depth understanding of reaction mechanisms using advanced characterization technologies and potential strategies for developing novel photoelectrodes and advanced photoelectrochemical water splitting devices are demonstrated. [ABSTRACT FROM AUTHOR]

Sustainable methods of clean fuel production are needed in the face of depleting oil reserves and to reduce carbon dioxide emissions. The technology of fuel cells for electricity production or the transport sector is already developed. However, a key missing element is a large-scale economical method of hydrogen production. The Cu-Cl thermochemical cycle is a promising thermochemical cycle to produce hydrogen. This paper focuses on a copper-chlorine (Cu-Cl) cycle and solar hydrogen production technology and describes the models how to calculate thermodynamic and transport properties. This paper discusses the mathematical model for computing the thermodynamic properties for pure substances and their mixtures such as CuCl in the solid phase with an aid of statistical thermodynamics and kinetic theory. The developed mathematical model takes into account vibrations of atoms in molecules and intermolecular forces. This mathematical model can be used for the calculation of thermodynamic properties of polyatomic crystals on the basis of the Einstein and Debye equations. We developed the model in the low-temperature and high-temperature region. All analytical data are compared with experimental results, and these show good agreement. For the transport properties, we have used kinetic theory. For fluid phase, we have calculated viscosity and thermal conductivity on the basis of the Chung-Lee-Starling kinetic model; for the solid phase, we have developed a model for calculations of thermal conductivity on the basis of electron and phonon contributions. [ABSTRACT FROM AUTHOR]

The fifth article in a series of five papers devoted to hydrogen energy digitalization. The article discusses the prospects for the introduction of digital technologies in the processes of industrial production, transportation and storage of hydrogen energy products. It is shown that the introduction of digitalization methods should be carried out within a single digital platform. The issues of digital security of hydrogen units, as well as the confidentiality of data transmission when using advanced information technologies, are considered. An increase in the pace of digitalization methods implementation can be achieved by training the personnel with competencies in interdisciplinary fields. A number of relevant problems that complicate the process of hydrogen industry digitalization are described. The requirements for the competencies of future experts in the interdisciplinary field are outlined. [ABSTRACT FROM AUTHOR]

The first article in a series of five papers devoted to hydrogen energy digitalization. The article discusses the prospects of hydrogen energy use as an alternative to fossil fuels, the objectives of using hydrogen as an energy source, and the problems that arise with it. Methods for obtaining energy from hydrogen without accompanying adverse emissions into the environment are described. The impact of the economy digitalization on production processes, as well as the most popular digital technologies and their role in hydrogen energy are shown. The digital processes available and currently being implemented, as well as promising, developing technologies for the transition to digitalization, are presented. [ABSTRACT FROM AUTHOR]

Visible light-driven hydrogen production by water splitting has attracted much attention because of its advantages of low cost, relative safety, and environmental friendliness. In this paper, a series of Ni-MOF-74 materials, Ni-MOF-74(X), with different morphologies and structures were synthesized by controlling the amount (X mL) of added water. Then, various CdS/Ni-MOF-74 composites were prepared by simple mechanical mixing of Ni-MOF-74(X) and CdS nanoparticles. The morphology and structures of CdS, Ni-MOF-74(X), and CdS/Ni-MOF-74(X) were analyzed by SEM, TEM, XRD, FT-IR, BET, and XPS. The optical properties of the composites were analyzed by UV–visible DRS, PL, TRPL, and photoelectrochemical experiments. The results show that Ni-MOF-74 is formed with a Ni3(OH)2(H2O)2(tp)2 structure (tp: terephthalate) at low water amounts and with a [Ni3(OH)2(H2O)4(tp)2]·2H2O structure when sufficient water was present to promote its formation. Mixed structures of Ni-MOF-74 containing Ni3(OH)2(H2O)2(tp)2 and [Ni3(OH)2(H2O)4(tp)2]·2H2O are formed when the water amount is between 5 and 40 mL. The CdS/Ni-MOF-74(15) composite has the best photocatalytic hydrogen evolution performance under visible light irradiation, and the maximum produced hydrogen amount is 3117.9 μmol after 3 h, which is 12.8 times that of pure CdS nanoparticles. The composite of CdS and Ni-MOF-74 with a mixed structure exhibits better photocatalytic hydrogen production performance than the composite based on Ni-MOF-74 with a single structure. As an explanation for the superior activity, a double type II heterostructure is formed by CdS and Ni-MOF-74 with two structures. The photogenerated electrons in the conduction band (CB) of CdS spontaneously transfer to the CB of Ni-MOF-74, which is beneficial to the improvement in the separation of photogenerated carriers in hydrogen evolution. [ABSTRACT FROM AUTHOR]

The first in a series of five papers devoted to cryogenic technologies of hydrogen energy. The article discusses the prospects of using hydrogen energy as an alternative for fossil fuel, the purpose of using hydrogen as an energy source and the problems that arise in this case. The methods of obtaining energy from hydrogen without accompanying adverse emissions into the environment are described. [ABSTRACT FROM AUTHOR]