Higher Amount Of Hydrogen Research Articles

Influence of hydrogen uptake on additive manufacturing and conventional austenitic stainless steels 316L

This study investigates the hydrogen embrittlement resistance of 316L stainless steels fabricated via conventional manufacturing (CM) and directed energy deposition (DED) additive manufacturing (AM). The hydrogen effect on the mechanical properties of these samples has been examined through a combination of microstructural investigation correlated with hydrogen solubility and trapping. Results show the CM sample has a lower solubility of hydrogen with a relatively low dislocation density. In the case of the as-built AM sample, the higher amount of hydrogen is linked with a deterioration in the mechanical behaviours of the steel (strength/elongation) and a higher hydrogen embrittlement sensitivity. This deterioration can be attributed to the higher misorientation density in AM material with a larger grain size. Conventionally, global hydrogen concentration is measured from thermal desorption spectroscopy (TDS), however this study presents a new measurement using glow discharge optical emission spectroscopy (GDOES). This method provides a new insightful understanding of hydrogen embrittlement with local hydrogen distribution and a comparison for existing standards.

The influence of inoculum source and pretreatment on the biohydrogen production in the dark fermentation process

The production of biohydrogen from food waste (FW) by dark fermentation (DF) is a promising technology for commercialisation, as it is both a clean fuel and a suitable means of sustainable waste management. The described experiments compared the biohydrogen production yields obtained after the use of inoculum from two different sources: digested sludge from the wastewater treatment plant (WWTP) in Lodz and sludge from the anaerobic treatment of dairy industry wastewater (DIW) (unconcentrated and double-concentrated). In addition, the effect of different temperatures (70, 90 and 121°C) of inoculum pretreatment on the biohydrogen production in DF was tested. The process was carried out batchwise at 37°C. The highest yield of hydrogen production was obtained after the inoculum pretreatment at 70°C. In addition, a higher amount of hydrogen could be obtained by using sludge from the WWTP as the inoculum (96 cm3 H2/gTVSFW) than unthickened sludge from the DIW (85 cm 3 H 2/g TVSFW). However, after thickening the sludge from the dairy industry, and at the same time balancing the dry matter of both sludges, the hydrogen production potential was comparable for bothsludges (for the WWTP sludge – 96 and for the DIW sludge – 93 cm 3 H 2/g TVSFW). The kinetics of hydrogen production was described by modified Gompertz equation, which showed a good fit (determination coefficient R2 between 0.909 and 0.999) to the experimental data.

Effects of cellulose contamination on polystyrene recycling to styrene monomer via microwave pyrolysis

The increasing population and by extension the plastic waste increasing rate requires innovative waste management mitigation solutions, especially for a challenging polymer such as polystyrene. However, the presence of a broad range of contaminants in its waste stream, cellulose-based contaminants being one of the most prevalent, hinders polystyrene recycling. Herein, a microwave co-pyrolysis of polystyrene and cellulose was carried out to recycle styrene as monomer and to investigate the synergy between both reactants at 500°C. Polystyrene pyrolysis presented a high styrene yield of 0.355g styrene/g polystyrene; while as the cellulose content increased, higher amounts of hydrogen are produced, leading to the hydrogenation of styrene into ethylbenzene and other styrenic derivatives such as 1,4-Diphenyl-2-butene and 1,3-Diphenyl-1-butene. A noticeable 29% decrease in styrene yield was observed for an equal amount of polystyrene and cellulose. At the same conditions, the detrimental effect of the co-pyrolysis also involved the reduction of the oil yield, from 58.9%, polystyrene pyrolysis, to 30.2%. The negative synergy between cellulose and polystyrene co-pyrolysis for the recycling of styrene monomer indicates that polystyrene waste streams must be handled thoroughly prior to being recycled.

Identification and evaluation of most promising CO2 utilization technologies: Multi criteria decision analysis and techno-economic assessment

Utilization of captured CO2 as a feedstock for the synthesis of valuable products offers an option for supporting climate change objectives and enabling a circular economy. Therefore, there is an increasing attention from governments and industry for promoting the further development of CO2-based applications. Given the multitude of CO2 utilization pathways that are far from equal, a comprehensive assessment is required to identify the most promising options for further development. This study aims to develop a consistent approach for comparing CO2 utilization pathways in terms of multiple criteria and scenarios. To this end, 133 utilization pathways were identified from the literature and evaluated using a Multi Criteria Decision Analysis tool, which is based on an Analytic Hierarchy Process, for three different scenarios. These analyses incorporated technology readiness level, global market size, global market price, CO2 utilization volume, and CO2 retention time as screening criteria. Also, three different scenarios, including Economic Vision, Environmental Vision, and Immediate Environmental Action, were considered to make a decision that reflects the preferences of different decision makers. The results show that calcium carbonate, ethylene, ethylene oxide, methane, polyethylene, polypropylene, syngas, synthetic fuel, and urea are the most promising CO2-based products with respect to the three considered scenarios. As a last step, a general framework was developed to calculate the minimum selling price of the selected CO2 utilization pathways to provide comparable economic results. The highest minimum selling prices were associated with polyethylene and ethylene oxide, where CO2 is incorporated in the respective production process indirectly through another reactant and the highest amount of hydrogen is required.

Hydrogen diffusion in proton-exchanged congruent Lithium Niobate during post-annealing

We investigated the diffusion of hydrogen during post annealing of proton-exchanged congruent LiNbO3 single crystals in the temperature range between 200 and 400 °C. Proton exchange was done in benzoic acid with 3.6 mol% lithium benzoate added. This process results in a 180 nm thin surface layer with a sharp interface where Li is substituted by H for about 45%. Depth profile analysis was carried out by secondary ion mass spectrometry. From the experimental results, diffusivities were extracted which follow the Arrhenius law with an activation enthalpy of diffusion of (1.39 ± 0.17) eV. The diffusivities are about two orders of magnitude lower than hydrogen tracer diffusivities in pure and in proton-exchanged LiNbO3 but are in good agreement to effective interdiffusion coefficients, governing the proton exchange. Also the activation energy for the latter case of (1.24 ± 0.04) eV is identical within error limits. The results indicate that the diffusional redistribution of high amounts of hydrogen in LiNbO3 is an interdiffusion process between H and Li that is governed by the migration of Li.

Oxygen and nitrogen plasma modifications of ZnCuCo LDH-graphene nanocomposites for photocatalytic hydrogen production and antibiotic degradation

Development of efficient, non-precious, and stable photocatalytic materials have become a prominent area of research in the energy production and environmental remediation fields. In this study, oxygen and nitrogen plasma-modified graphene (NOG) was used to support nitrogen-doped ZnCuCo layered double hydroxide (NLDH). The synergistic combination of oxygen functionalities and nitrogen doping significantly improved the photocatalytic activity of NLDH-NOG. The plasma modification introduced oxygen-containing functional groups on the surface of NOG, enhancing its hydrophilicity and facilitating efficient contact between NLDH and NOG. SEM and TEM images confirmed the uniform deposition of LDH and NLDH onto the plasma-modified graphene surface. Furthermore, nitrogen doping modified the Fermi levels, reducing the band gap of NLDH and promoting electron migration between NLDH and NOG, resulting in prolonged lifetimes of photogenerated charge carriers. Although the bare LDH was inactive in the photocatalytic hydrogen generation, NLDH-NOG produced a high amount of hydrogen under visible light illumination, benefiting from the large surface area (233 m2g−1), improved light absorption, and enhanced charge separation. Additionally, the photodegradation of sulfanilamide (SA) was significantly enhanced compared to bare LDH. electron spin resonance (ESR) spectroscopy and scavenging experiments indicated that O2– and OH radicals played important roles in the photocatalytic degradation of SA. Based on the identification of intermediate compounds, a plausible reaction pathway for SA photodegradation was proposed. This study reveals the applicability of environmentally-friendly plasma modification of LDH-graphene nanocomposite with highly-efficient and durable photocatalytic activities towards hydrogen generation and pollutant degradation.

Mechanisms of hydrogen absorption, trapping and release during galvanostatic anodization of high-strength aluminum alloys

The initial growth of a porous alumina layer and the hydrogen absorption during galvanostatic anodization were studied using high-resolution electron microscopy, thermal desorption spectroscopy, and hydrogen microprint technique. The nanostructure of the alumina layer depends strongly on the anodization time. The embryo of pores grows as the thickness of the oxide layer increases, and a porous alumina layer is formed until the voltage reached its maximum value. Eventually, the connected pores to the substrate appear in a steady-state voltage region that acted as hydrogen pathways. The substrate does not show delayed embrittlement after the early and late stages of anodization, which is attributed to the low amount of absorbed hydrogen during the anodization. In the middle stage of the anodization, a higher amount of hydrogen is trapped in the substrate/layer interface and then migrates inward into the alloy when the specimen is subjected to stress resulting in delayed hydrogen embrittlement.

Experimental and Simulation Study on Coproduction of Hydrogen and Carbon Nanomaterials by Catalytic Decomposition of Methane-Hydrogen Mixtures

Among all hydrocarbons, the methane molecule contains the highest amount of hydrogen with respect to carbon. Therefore, the catalytic decomposition of methane is considered as an efficient approach to produce hydrogen along with nanostructured carbon product. On the other hand, the presence of hydrogen in the composition of the initial gas mixture is required for the stable operation of the catalyst. In present work, the experiments on the catalytic decomposition of methane–hydrogen mixture were performed in a flow-through quartz reactor equipped with McBain balances under atmospheric pressure. The catalyst NiO-CuO/Al2O3 was prepared by the mechanochemical activation technique. The maximum carbon yield of 34.9 g/gcat was obtained after 2 h of experiment at 610 °C. An excess of hydrogen in the reaction mixture provided the long-term activity of the nickel–copper catalyst. The durability tests ongoing for 6 h within a temperature range of 525–600 °C showed no noticeable deactivation of the catalyst. Two kinetic models, D1a and M1a, were proposed for the studied decomposition of the methane–hydrogen mixture over the nickel–copper catalyst. The kinetic constants for these models were determined by means of mathematical modelling.

Utilization of pyrolytic oil and hydrogen enriched syngas from single feedstock (delonix regia) through pyrolysis process and its influence on performance and emission characteristics in CI engine

The main objective of the present investigation is to conduct the performance, combustion and emission analysis of CI engine operated using hydrogen enriched syngas (pyrolytic gas) and biodiesel (pyrolytic oil) as dual fuel mode condition. Both the pyrolytic oil and syngas is obtained from single feedstock delonix regia fruit pod through pyrolysis process and then pyrolytic oil is converted into biodiesel through esterification. Initially biomass is subjected to thermal degradation at various pyrolysis temperature ranges like 350–600 °C. During the pyrolysis process syngas, pyrolytic oil and char are produced. The syngas is directly used in the CI engine and pyrolytic oil is converted into biodiesel and then used in the CI engine. The pyrolytic oil and syngas is subjected to FTIR and GC/TCD analysis respectively. The syngas analysis confirms the presence of various gases like H2, CH4, CO2, CO and C2H4 in different proportions. The various proportions of the syngas is mainly depending upon the reactor temperature and moisture content in the biomass. The syngas composition varies with increase in the temperature and at 400 °C, higher amount of hydrogen is present and its composition are H2 28.2%, CO is 21.9%, CH4 is 39.1% and other gases in smaller amounts. The biodiesel of B20 and syngas of 8lpm produced from the same feedstock are considered as test sample fuels in the CI engine under dual fuel mode operation to study the performance and emission characteristics. The study reveals that BTE has slight increase than diesel of 1.5% at maximum load. On the another hand emission like CO, HC and smoke are reduced by 15%,25% and 32% respectively at full load condition, whereas NOx emission is increased at all loads in the range of 10–15%. Therefore B20+syngas of 8lpm can be used as an alternative fuel in CI engine without any modification and major products from pyrolysis process with waste biomass is fully used as fuel in the CI engine.

Parametric studies over a plasma co-gasification process of biomass and coal through a restricted model in Aspen plus

Plasma gasification is considered an emerging technology within the so-called waste-to-energy technologies. The pure equilibrium models have been failing to estimate the amounts of the syngas components, especially the methane quantity. In this investigation, a restricted or quasi-equilibrium model was developed in Aspen Plus® to evaluate the performance of the plasma co-gasification process of biomass and coal. The developed model was validated against literature data. A comprehensive parametric study was performed considering the variation of the equivalence ratio, biomass ratio, temperature, and steam to feedstock ratio on the quality of syngas and hydrogen production. Three gasifying agents (air, steam, and oxygen) were used. The syngas lower heating value and the cold gas efficiency are taken as a measure of the syngas quality and process efficiency. The developed restricted model shows to estimate the amount of methane much closer to the experimental data than pure equilibrium models. The highest amount of hydrogen was obtained for steam followed by pure oxygen and lastly for the air as gasifying agents. The use of coal in the feedstock mixture allows obtaining higher LHV of the syngas and CGE of the process. The results of this parametric study represent a humble contribution to the increase of plasma gasification technology market penetration.

Interfacial Ni active sites strike solid solutional counterpart in CO2 hydrogenation

Ni enhanced CeO2 based catalysts were tested in CO2 hydrogenation reaction with the objective to investigate the importance and role of Ni0 and Ni0-NiO-CeO2−x interfaces. Two materials were prepared: a 4 mol% NiO/CeO2 interfacial oxide where CeO2 supports NiO nanoparticles was produced by wet impregnation method and a Ce0.96Ni0.04O2 mixed oxide was obtained by co-precipitation of Ce3+ and Ni2+ ions. Besides these materials, pure NiO and CeO2 were also synthesized and tested, serving as reference materials. HRTEM, TPR, XRD, BET, EDS, Raman spectroscopy, and XPS were used for the characterization of the catalysts. The activity and selectivity strongly depended on metallic Ni content, which is tunable by the temperature of hydrogen pretreatment. The impregnated catalyst with significant metallic content exhibited high activity and high methane selectivity. The mixed oxide was more resistant to reduction, in the case of both the Ni2+ and Ce4+ species, thus it has low activity with high CO selectivity. The activity and methane selectivity increased considerably by increasing the metal content or higher hydrogen pretreatment temperature. Operando DRIFTS experiments suggested that bicarbonate and formate intermediates play important role in CO2 hydrogenation in both types of catalysts. The reduced Ni particles help to produce the high amount of hydrogen needed for the hydrogenation of formate to methane. It turned out that the metallic Ni not only catalyzes the methane production from formate but also the bicarbonate-formate transformation. The most important factor in the high performance of these catalysts is the Ni0/NiO ratio in the Ni0-NiO-CeO2−x interface.

Impact of Polymers on Magnesium-Based Hydrogen Storage Systems.

In the present scenario, much importance has been provided to hydrogen energy systems (HES) in the energy sector because of their clean and green behavior during utilization. The developments of novel techniques and materials have focused on overcoming the practical difficulties in the HES (production, storage and utilization). Comparatively, considerable attention needs to be provided in the hydrogen storage systems (HSS) because of physical-based storage (compressed gas, cold/cryo compressed and liquid) issues such as low gravimetric/volumetric density, storage conditions/parameters and safety. In material-based HSS, a high amount of hydrogen can be effectively stored in materials via physical or chemical bonds. In different hydride materials, Mg-based hydrides (Mg–H) showed considerable benefits such as low density, hydrogen uptake and reversibility. However, the inferior sorption kinetics and severe oxidation/contamination at exposure to air limit its benefits. There are numerous kinds of efforts, like the inclusion of catalysts that have been made for Mg–H to alter the thermodynamic-related issues. Still, those efforts do not overcome the oxidation/contamination-related issues. The developments of Mg–H encapsulated by gas-selective polymers can effectively and positively influence hydrogen sorption kinetics and prevent the Mg–H from contaminating (air and moisture). In this review, the impact of different polymers (carboxymethyl cellulose, polystyrene, polyimide, polypyrrole, polyvinylpyrrolidone, polyvinylidene fluoride, polymethylpentene, and poly(methyl methacrylate)) with Mg–H systems has been systematically reviewed. In polymer-encapsulated Mg–H, the polymers act as a barrier for the reaction between Mg–H and O2/H2O, selectively allowing the H2 gas and preventing the aggregation of hydride nanoparticles. Thus, the H2 uptake amount and sorption kinetics improved considerably in Mg–H.

Quantitative analysis of boron–hydrogen pair dynamics by infrared absorption measurements at room temperature

The ability of hydrogen quantification in crystalline silicon in concentrations as low as 1014cm−3 becomes fairly important in regard to hydrogen-related degradation phenomena in silicon devices generally and solar cells particularly. The method presented here allows for direct boron–hydrogen pair quantification and, therefore, allows inference on total hydrogen content. Hydrogen-rich amorphous silicon nitride was deposited on stripes of boron-doped float-zone silicon (1 Ωcm), which were exposed to a rapid high temperature step to introduce relatively high amounts of hydrogen into the wafer. Infrared absorption spectra, which have been corrected for multiple reflection and free-carrier absorption, show absorption related to the boron–hydrogen stretching mode at ν~=1868cm−1 with varying strengths during formation and subsequent dissociation of boron–hydrogen pairs triggered by annealing in the dark at 220°C. Since the measurements were performed at room temperature, this method allows investigations with little effort and standard laboratory equipment. Furthermore, the change in free-carrier absorption (described by Drude’s theory) is used to derive the change in hole concentration concurring with the formation and dissociation of boron–hydrogen pairs. The latter is found to fairly match not only the changing strength in absorption of the stretching mode, but also the change in hole concentration obtained by highly sensitive resistivity measurements. The comparison of stretching mode absorption strength and change in resistivity allows for a calibration of specific absorption, yielding a calibration factor ABH. This calibration was performed with the absorption α [ABHα=(4.2±0.3)×1015cm−1] as well as with the quotient of absorption and wavenumber α/ν~ [ABHα/ν~=(7.8±0.6)×1018cm−2].

Enhanced Hydrogen Production at Optimum pH for the Recovery Cycle of β-FeOOH.

In the photo-Fenton reaction, highly reactive oxygen species are generated on UV irradiation of β-FeOOH, which contributes significantly to hydrogen production. The production process was performed by adjusting the pH of the solution. The effect of acid concentration on hydrogen production was analyzed in this study, and the difference in the amount of hydrogen gas produced in each sample with different pH values was determined. X-ray powder diffraction (XRD) measurements of the samples corresponding to the peaks of β-FeOOH were compared with the reference data, and crystallite sizes were calculated by the Scherrer equation using XRD patterns. The rod-like structure of the sample particles was revealed by scanning electron microscopy. A higher amount of hydrogen was produced at lower pH, and these results confirmed that pH plays an important role in hydrogen production.

On the implication of mobile hydrogen content on the surface reactivity of an austenitic stainless steel

The Influence of hydrogen on the corrosion behavior of an AISI 316 L austenitic stainless steel in borate buffer solution is studied after a cathodic pre-charging step. A high amount of hydrogen is absorbed and forms a concentration gradient from the surface to the bulk with a path length of about 80 µm. The surface reactivity in the passive regime after the cathodic charging and during the hydrogen desorption is investigated with a large set of electrochemical and physico-chemical technics: electrochemical polarization, EIS, Mott-Schottky analysis and XPS. This approach allows to demonstrate that surface reactivity increases drastically with hydrogen absorption. This effect is mostly due to mobile hydrogen and is mainly reversible with its desorption. Hydrogen absorption and desorption have a small impact on the passive layer composition and thickness. However, the hydrogen induces an increase in the dissolution rate, which is discussed based on the Point Defect Model. Present results suggest that the impact of hydrogen on the surface reactivity is a consequence of a strong increase in the mobility of anionic vacancy and/or hydrogen oxidation.

A numerical approach to design a type II box-shaped pressure vessel with inner tension struts

The use of shared vehicle architectures with BEVs offers a high potential for FCEVs in terms of cost reduction. Therefore, the hydrogen must be stored in the box-shaped design space in the underbody of the vehicles, where the battery in BEVs is located. Box-shaped pressure vessels show the potential to store high amounts of hydrogen in this design space. An optimal design of a type I box-shaped pressure vessel with inner tension struts is investigated in literature. In this study, the relatively low efficiency of this type of pressure vessel is presented first. This motivates to work out the possibilities to increase the efficiency by reducing the total weight. Therefore, a numerical analysis is conducted to reinforce the vessel wall with fiber reinforced composite in the main section of this study. In a first step the possible measures to reinforce the pressure vessel are analyzed and evaluated. Then, a basic design, which serves as a baseline for the numerical studies, is determined analytically. Using a numerical model, the structure of the reinforcement and the acting loads are investigated with finite element method in parametric studies varying several parameters. Based on the knowledge gained, optimal design parameters are derived. These design parameters allow a comparison of the pressure vessel efficiency with other pressure vessel types and enable the evaluation of this vessel concept.

Study on Boron–Hydrogen Pairs in Bare and Passivated Float‐Zone Silicon Wafers

This study deals with the dynamics of the formation and dissociation of boron–hydrogen (BH) pairs in crystalline silicon during a rapid high‐temperature treatment and subsequent dark annealing between 200 and 300 °C. Highly accurate resistivity measurements are used to detect BH pairs in chemically polished B‐doped float‐zone silicon. It is found that an unexpecteded high amount of hydrogen is present in the as‐purchased wafers. Hydrogen is initially mostly paired to boron but can be dissolved by a short high‐temperature firing step. If a firing step (530 °C) is applied to bare, unpassivated Si wafers, most of the initial BH pairs are dissolved, and hydrogen dimers () form. With increasing peak temperature, an increasing amount of hydrogen leaves the system, while the proportion of BH increases. Additional hydrogen can be introduced by firing a wafer passivated with plasma‐enhanced chemical vapor deposition (PECVD) H. A three‐state model shows a good agreement with the measured data for both bare and coated samples as well as for different annealing temperatures. With increasing dark annealing temperatures, the BH dynamics accelerates, whereas the maximum BH concentration reached decreases. For temperatures above 280 °C, significant changes in the reaction dynamics are observed.

A Development of Pore Network Model Coupled Thermal Transport for Hydrophilic Porous Media of PEM Electrolyser

Hydrogen is a highly promising energy carrier vector. Water electrolysis process that provides splits of water to hydrogen and oxygen through the electricity has gained great recognition for hydrogen production because it provides high conversion efficiency, clean and purified hydrogen in recent years. A Polymer Electrolyte Membrane electrolyser that brings important advantages such as compactness, and the ability to work at low operating temperature, is an electrochemical device. From the gas channels in the cathode, the water enters the hydrophilic porous transport layer (PTL), also known as the gas diffusion layer (GDL), to the catalyst layer (CL) in which the electrolysis reactions occur.At high current densities (higher than 1 A/cm2), the PEM electrolyser is also favorable to produce a high amount of hydrogen; however, management of heat and mass transfer in the GDL becomes crucial as the two-phase flow occurs, and can be lead to hot spots. Moreover, the mass transport overpotentials become important issues at high current densities and lead to be 25% losses in the overall electrolyzer overpotential. A development of model is crucial to understand and enhance the heat and mass transport mechanisms in CL-GDL interface. Here, pore network model (PNM) has gained a significant interest as it offers strong tool to simulated multiphase flow in three-dimensional (3D) porous media for electrochemical energy conversion. The principle behind of this modelling approach is that a porous medium behaves as a network of pores that connected by throats. Through this framework, the discretization approach to transport modelling becomes dramatically simple, and the computational cost and time are reduced among the continuum modelling approaches (e.g., Lattice-Boltzmann, CFD).In this work, to the best knowledge of authors, the first pore network model coupled heat transfer model is developed to characterize available GDL. Here, the pore network is extracted from the micro CT image of a hydrophilic GDL through the Snow algorithm employed in OpenPNM software (An open-source Pore Network Modeling Package) and reconstructed in this environment, while the geometry of catalyst layer is created randomly. The effective two-phase 2D model is developed to predict water transport in the GDL and CL through the percolation algorithm. For this purpose, the sink and source terms are employed for some pores in the network (especially near GDL-CL interface) according to electrolyser operating conditions. Similarly, heat transport equations are applied for each pore in the network with adding source and sink terms due to the evaporation and condensation, respectively according to operating conditions. Therefore, under electrolyser operating conditions, the heat and mass transfer performance of GDL and especially in GDL-CL interface are investigated. Moreover, the effect of GDL-CL morphology (e.g., pore and throat sizes, and porosity) on heat and mass transport mechanism is investigated in detail.

CdS decorated MnWO4 nanorod nanoheterostructures: a new 0D-1D hybrid system for enhanced photocatalytic hydrogen production under natural sunlight.

Constructing a heterostructure is an effective strategy to reduce the electron–hole recombination rate, which enhances photocatalytic activity. Here, we report a facile hydrothermal method to grow CdS nanoparticles on MnWO4 nanorods and their photocatalytic hydrogen generation under solar light. A structural study shows the decoration of hexagonal CdS nanoparticles on monoclinic MnWO4. Morphological studies based on FE-TEM analysis confirm the sensitization of CdS nanoparticles (10 nm) on MnWO4 nanorods of diameter-35 nm with mean length ∼100 nm. The lower PL intensity of MnWO4 was observed with an increasing amount of CdS nanoparticles, which shows inhibition of the charge carrier recombination rate. A CdS@MnWO4 narrow band gap semiconductor was employed for photocatalytic hydrogen generation from water under solar light and the highest amount of hydrogen, i.e. 3218 μmol h−1 g−1, is obtained which is 21 times higher than that with pristine MnWO4. The enhanced photocatalytic activity is ascribed to the formation of a CdS@MnWO4 nanoheterostructure resulting in efficient spatial separation of photogenerated electron–hole pairs due to vacancy defects. More significantly, direct Z-scheme electron transfer from MnWO4 to CdS is responsible for the enhanced hydrogen evolution. This work signifies that a CdS decorated MnWO4 nanoheterostructure has the potential to improve the solar to direct fuel conversion efficiency.

Integrated adsorption steam gasification for enhanced hydrogen production from palm waste at bench scale plant

The generation of hydrogen-enriched synthesis gas from catalytic steam gasification of biomass with in-situ CO2 capture utilizing CaO has a high perspective as clean energy fuels. The present study focused on the process modeling of catalytic steam gasification of biomass using palm empty fruit bunch (EFB) as biomass for hydrogen generation through experimental work. Experiment work has been carried out using a fluidized bed gasifier on a bench-scale plant. The established model integrates the kinetics of EFB catalytic steam gasification reactions, in-situ capturing of CO2, mass and energy balance calculations. Chemical reaction constants have been calculated via the parameters fitting optimization approach. The influence of operating parameters, mainly temperature, steam to biomass, and sorbent to biomass ratio, was investigated for the hydrogen purity and yield through the experimental study and developed model. The results predicted approximately 75 vol% of the hydrogen purity in the product gas composition. The maximum H2 yield produced from the gasifier was 127 gH2/kg of EFB via experimental setup. The increase in both steam to biomass ratio and temperature enhanced the production of hydrogen gas. Comparing the results with already published literature showed that the current system enables to produce a high amount of hydrogen from EFB.