Reaction Of Hydrogen Research Articles

Thermodynamic Study of H2-FeO Based on the Principle of Minimum Gibbs Free Energy

Studies have shown that the reduction of wustite is the limiting factor in the ironmaking process, whether in hydrogen-based shaft furnaces, hydrogen-rich blast furnaces or smelting reduction vessels. The study of the thermodynamic conditions for the reduction of molten wustite by hydrogen is of great significance for the optimization of the ironmaking process, energy saving and emission reduction. Previous studies have mostly focused on the thermodynamic study of the reduction at a lower temperature, but the data at high temperatures are different, which makes the calculation of thermodynamics difficult. Moreover, it is difficult to obtain experimental evidence for the data at high temperature, so calculation is needed to verify its feasibility. In this paper, a thermodynamic calculation model for the reduction of molten wustite by hydrogen based on the principle of minimum Gibbs free energy is developed. The enthalpy changes of the reaction at different temperatures and the partial pressure of hydrogen required for the reaction to occur are calculated, and the energy change during the reaction is analyzed. The results show that the partial pressure of hydrogen for the reduction of molten wustite by hydrogen at high temperatures decreases from 0.67 at 1650 K to about 0.65 at 2000 K. The enthalpy changes of reaction at 1873 K are only 1/4 to 1/3 of that at 1173 K compared with that at the corresponding temperature between hydrogen for the reduction of molten wustite (1873 K) and hydrogen-based shaft furnace reaction (1173 K). Interestingly, the thermodynamic calculations show that the effect of energy absorption in the gas–liquid reaction of hydrogen with wustite at high temperatures is much lower than in the gas–solid reaction zone at low temperatures. These results indicate that the energy change of the reduction of molten wustite by hydrogen at high temperatures is better than that of hydrogen reduction at low temperatures, and the thermodynamic conditions are more favorable, with slightly different results from different thermodynamic databases, but the general trend is the same. The results of this study will provide fundamental data to support new hydrogen metallurgy technologies in the future. If its correctness can be verified experimentally in the future, this result will be promoted to the development of a new alternative ironmaking technology, hydrogen-based smelting reduction.

Hydrogen Reactions in c‐Si:B During Illumination at Room Temperature

Herein, effects related to reactions involving hydrogen during carrier injection at room temperature in boron‐doped Czochralski‐grown silicon wafers are investigated. It is shown that these conditions lead to boron–oxygen defect regeneration. Under these conditions, bulk material quality degradation induced by a dark annealing can be temporarily recovered in the same way as light and elevated temperature‐induced degradation. Dissociation of boron–hydrogen pairs by carrier injection at room temperature is observed in parallel. These observations are discussed within the framework of known hydrogen reactions. With this study, significant aspects of hydrogen‐related meta‐stabilities at temperatures that are most relevant for solar modules in moderate climates are covered.

The Self-Reduction during the Thermal Decomposition of an Ammonium Molybdate

In the hydrometallurgical process of molybdenum using ammonia solution, ammonium paramolybdate tetrahydrate (APT: (NH4)6Mo7O24·4H2O) is produced as an intermediate product after a crystallization step. ATP is then thermally decomposed at a high temperature to give MoO3, which is reduced by hydrogen gas in a two-stage process to reduce molybdenum metal powder as the final product. If APT is pre-dried at an appropriately low temperature to remove the crystal water corresponding to 4 mol per mol of APT, it changes into (NH4)4Mo5O17, and the content of residual ammonia, which can be utilized as a reductant, in the ammonium molybdate increases. In this regard, the self-reducing potential of (NH4)4Mo5O17 was examined in this study through the effectiveness analysis of the residual ammonia component as a reductant for the primary hydrogen reduction step. In a series of experimental work on the thermal decomposition of (NH4)4Mo5O17 in an inert atmosphere, a maximum self-reduction degree of 18% was achieved. Based on this result, it can be expected that the metal powder can be manufactured in a more effective way than conventional processes in terms of hydrogen consumption and reaction time.

Hydrogen ortho-para conversion: process sensitivities and optimisation

Liquid hydrogen has potential as a storage vector for large-scale hydrogen transportation. Hydrogen liquefaction is however a highly energy intensive process, particularly due to the necessary exothermic spin-isomer conversion from ortho- to parahydrogen. We explore the operation of the main cryogenic plate-fin heat-exchangers (PFHXs) used in hydrogen liquefaction; simultaneous dynamic processes occurring within the PFHX include the heterogeneously catalysed spin-isomer conversion, heat transfer and pressure loss. In this work, these coupled processes are simulated for a 100 tonne/day hydrogen reactant cooled by a helium refrigerant in a PFHX. For the process configuration utilised in this work, a reactor volume of 24.0 m3 and a coolant flow rate of 600 tonne/day were necessary to achieve and outlet parahydrogen fraction of 0.99. Pressure drop through the PFHX packed bed was consistently negligible. We also explored the sensitivity towards model parameters. The outlet parahydrogen fraction is determined to be considerably (∼10 times) more sensitive to reaction rate kinetics relative to heat transfer: therefore, the reactor geometry will be primarily determined by conversion kinetics. The current quantitative understanding of these rate kinetics is however limited. Future experimental research thus needs to focus on quantifying ortho- to parahydrogen kinetics.Destination: Chemical Engineering and Processing: Process Intensification

Hydrogenation of C=N bonds on TiO2 surface: The effect of the Cu2O/TiO2 p-n heterojunction photocatalyst

As a widely used semiconductor photocatalyst, TiO2 has been explored in organic compounds hydrogenation. In this study, the hydrogenation of C=N bonds on the surface of TiO2 was accomplished for the first time utilizing Cu2O/TiO2 type-II (p-n) heterojunction. The probe reactions, hydrogenation of N-benzylphenylamine with benzyl alcohol, and N-methylation of amines with methanol exhibited that the hydrogenation of C=N bonds on TiO2 surface can be achieved through borrowing hydrogen reaction (BH, alcohols as hydrogen source). Additionally, the BH reaction rate could be improved by adding external H+ to the reaction system. The catalytic activity of Cu2O/TiO2 was discovered to remain at an efficient level even after six reaction cycles.

Role of Chiral Skeleton in Chiral Phosphoric Acids Catalyzed Asymmetric Transfer Hydrogenation: A DFT Study

Chiral phosphoric acids (CPAs) have received considerable attention due to their high activity for enantioselective transformations. However, the role of various chiral skeletons of CPAs in regulating the mechanism and enantioselectivity of asymmetric transfer hydrogenation has remained unclear. Density functional theory (DFT) calculations are performed to elucidate the role of chiral skeletons on the acidity, mechanism, enantioselectivity, and kinetic stabilities of transition states (TSs) in Asymmetric Transfer Hydrogen (ATH) reaction catalyzed by five CPAs. We found that the acidity of CPAs is strongly dependent on the chiral skeleton. The origin of enantioselectivity of ATH reaction arises from the differential noncovalent interactions between TSs and CPAs. Moreover, the shape and size of the catalyst pocket depending on chiral skeletons play key roles in the stability of TSs and the enantioselectivity of ATH. This study might facilitate to design and computationally screening of CPAs and guide the strategic choice of CPA skeletons to reduce the experimental workload.

Anti‐Corrosive SnS2/SnO2 Heterostructured Support for Pt Nanoparticles Enables Remarkable Oxygen Reduction Catalysis via Interfacial Enhancement

AbstractThe stability of Pt‐based catalysts for oxygen reduction reaction (ORR) in hydrogen fuel cells is seriously handicapped by the corrosion of their carbon supports at high potentials and acidic environments. Herein, a novel SnS2/SnO2 hetero‐structured support is reported for Pt nanoparticles (NPs) as the ORR catalyst, where Pt NPs are mainly deposited at the interfaces of SnS2 and SnO2 moieties. The Pt‐support interactions, which can be tuned by the concentration of the heterointerfaces, can accelerate the electronic transfer and enrich the electron density of Pt with a favorable shift of the d‐band center. In electrochemical measurements, the ORR mass activity (MA) of the optimal Pt‐SnS2/SnO2 catalyst at 0.9 V versus RHE (0.40 A mgPt−1) is four times higher than that of Pt/C. As for the stability, the electrochemical active surface area and MA of Pt‐SnS2/SnO2 are only decreased by 18.2% and 23.7% after 50 000 potential cycles at a high potential region (1.0–1.6 V), representing the best ORR stability among the reported Pt‐based catalysts. Density functional theory calculations indicate that the binding energy and migration barrier of Pt atom/cluster on the SnS2/SnO2 heterojunction are much higher relative to other supports, accounting for the outstanding stability of the catalyst.

Transition metal-catalysis in interrupted borrowing hydrogen strategy.

In recent times, the transition metal-catalyzed borrowing hydrogen (BH) and interrupted borrowing hydrogen (IBH) strategies have attracted much attention and represent atom- and step-economic processes to access diverse building blocks via various C-C and C-heteroatom bond-forming reactions. The advantages of these approaches include (i) use of feedstock chemicals, (ii) high atom economy, (iii) no pre-activation of the substrates, and (iv) producing water as the only by-product. In this context, several synthetic strategies have been developed in this regime for the past few decades. To the best of our knowledge, no review article describes the important concepts of interrupted borrowing hydrogen (IBH) reaction. This review article highlights the recent advances in the IBH strategy and its application in sustainable chemical synthesis, particularly C-C bond formation using methanol as a C1 source, synthesis of 3,3'-bisindolylmethanes (3,3'-BIMs), α-branched ketones/diketones, and regioselective alkylation of N-heterocycles.

Process parameters study of sanitary landfill leachate treatment using photo-Fenton-like systems

In this study, the effects of the combination of classical Fenton (CFP) and modified Fenton (MFP) processes with UV light on the treatment of sanitary landfill leachate have been investigated. Iron (Fe2+ and Fe0) dosage, hydrogen peroxide dosage, reaction time, pH and different UV lamps have been optimized to achieve high COD removal. In addition, zeroth, first and second order kinetic models are applied for all processes under optimum conditions. For CFP and MFP; optimum pH 3, reaction time 30 min, 4 g/kg TS Fe2+ and Fe0 and 5 g/kg TS H2O2 have been determined. The COD removal efficiency is determined as 48.86% for CFP and 59.27% for MFP under optimum conditions. COD removal efficiencies increased in photo Fenton application under UV light. The efficiency is found to increase under UVA light source from 48.86% to 49.17% and from 59.27% to 70.72% in in CFP and MFP, respectively. In the kinetic study, the highest R2 values are obtained in the CFP/UV process, while CFP and MFP are found to fit the 0th order kinetic model. In this study, it has been concluded that Fenton and photo Fenton applications are effective in reducing the COD values of landfill leachate.

2-(Indol-3-yl)- and 6-(pyrrol-2-yl)-substituted (bi)pyridine-based AIE-probes/fluorophores: synthesis and photophysical studies

A series of new indolyl- and pyrrolyl-substituted 2,2′-bipyridines were reported as push–pull fluorophores/probes by using a sequence of the nucleophilic substitution reaction of hydrogen (SNH) and inverse-demand Diels–Alder reaction.

Positioning hydrogen reaction sites by constructing CdS/CoNiMoS4 heterojunctions for efficient photocatalytic hydrogen evolution.

The high gravimetric energy density of hydrogen makes it an ideal chemical fuel to address the issues of fossil fuel depletion and environmental pollution. Even though transition metal sulfides (TMSs) have been extensively investigated as substitutes for noble metals, their effectiveness is still doubtful for practical applications. Herein, we introduce a facile and general strategy to fabricate heterojunctions with CdS nanorods and a multimetallic transition metal sulfide (CoNiMoS4) for enhanced photocatalytic activity. The CdS/CoNiMoS4 heterojunction will serve as a dual-function photocatalyst with enhanced visible light absorption capability offered by CdS and high charge transfer efficiency provided by CoNiMoS4 nanostructures. Moreover, CdS/CoNiMoS4 nanostructures exhibit the best photocatalytic performance to generate H2 with an amount of 31.9 mmol g-1 h-1, with a distinguished stability for over 25 h. This synthetic approach may offer a new strategy to create diverse heterojunctions with Earth-abundant multimetallic components, which may broaden their scope of application in catalysis.

INFLUENCE OF CATHODE MATERIAL ON COMBINED CATHODE PROCESSES IN AQUEOUS SOLUTIONS OF IRON(II) SULPHATE

Sulfuric acid is present in many enterprises for metal processing and manufacturing of metal parts. Existing methods of regeneration of spent solutions are not effective, in particular, spent sulfate solutions are neutralized with lye or waste from other industries containing solid carbonates and hydroxides. At the same time, sulfate waste is formed, which requires disposal at special landfills. Electrochemical regeneration of spent solutions of sulfate-acid treatment of steel solves the problem of disposal of such spent sulfate solutions with the inclusion of iron sulfates. The kinetics of combined cathodic processes in aqueous solutions of iron (II) sulfate at a concentration of 0.5 mol.·dm–3 of iron (II) sulfate, depending on the cathode material was studied. The research methodology was as follows: model aqueous solutions with a composition (mol∙dm–3): 0.5 iron (II) sulfate with the addition of 0.5 sulfuric acid and a control solution – 1.0 sulfuric acid were prepared from chemicals of high stage of purification by dissolution in distilled water. The study of the kinetics of combined cathodic processes in model aqueous solutions was carried out by the method of linear voltammetry using the MTech PGP-500 S potentiostat. The auxiliary electrode is platinum. The reference electrode is mercury sulfate. Determination of iron (II) ions in the solution was carried out by the permanganatometric method. Based on the analysis of the obtained current-voltage curves, the effectiveness of the application of electrochemical regeneration of model solutions of iron (II) sulfate with sulfuric acid was established, which makes it possible to cathodically deposit iron in the form of foil or metal powder, and through the course of the anodic process - convert sulfates into sulfuric acid. During this process, oxidation of Fe2+ to Fe3+ takes place at the slightly soluble anode. Therefore, it is proposed to use polymer porous diaphragms to prevent Fe2+ from entering the anode space. Platinum and copper were used as cathode material. The choice of cathode material was based on different electrochemical properties of these metals in relation to the hydrogen reaction. The balance research on the regeneration of the model solution was carried out in a three-chamber electrolyzer. The initial test solution was fed into the middle chamber. The cathodic current density was 0.025 and 0.035 A∙cm–2, the working area of the anode and cathode was 85 cm2. A compact iron deposit was obtained on the cathode with 08X12N10T, which peeled off. The analysis of the cathode deposit showed the presence of 0.065% hydrogen in iron. Output according to the current of iron was 92%. The end of the Tafel section of the course of cathodic reduction of iron with electrochemical control occurs due to Fe2+ concentration limitations and the ohmic resistance of adsorbed hydrogen at the boundary of heterogeneous phases. It is proposed to eliminate these limitations due to electrolyte mixing.

Short-Range Nanoreaction Effect on the Hydrogen Desorption Behaviors of the MgH2–Ni@C Composite

Doping a catalyst can efficiently improve the hydrogen reaction kinetics of MgH2. However, the hydrogen desorption behaviors are complicated in different MgH2-catalyst systems. Here, a carbon-encapsulated nickel (Ni@C) core-shell catalyst is synthesized to improve the hydrogen storage properties of MgH2. The complicated hydrogen desorption mechanism of the MgH2-Ni@C composite is elucidated. The experimental and theoretical calculation results indicate a short-range nanoreaction effect on the hydrogen desorption behaviors of the MgH2-Ni@C composite. The Ni@C catalysts and the adjacent MgH2 form nanoreaction sites along with preferential hydrogen desorption. The new interface between the in situ formed Mg and residual MgH2 contributes to the subsequent hydrogen desorption. With the nanoreaction sites increased via adding more catalyst, the short-range nanoreaction effect is more prominent; as a comparison, the interface effect becomes weaker or even disappears. In addition, the core-shell structure catalyst shows ultrahigh structural stability and catalytic activity, even after 50 hydrogen absorption and desorption cycles. Hence, this study provides new insights into the complicated hydrogen desorption behaviors and comes up with the short-range nanoreaction effect in the MgH2-catalyst system.

Catalytic combustion type optical fiber Bragg grating hydrogen gas sensor using platinum-loaded fumed silica powder

In order to ensure the safety of hydrogen energy system, a robust and reliable hydrogen sensor device with an optical fiber Bragg grating (FBG) has been developed. The sensing mechanism is based on temperature changes in the device induced by the heat of the catalytic reaction of hydrogen on platinum-loaded fumed silica catalyst powder. Through optimization of the preparation conditions for the catalyst, which is a hydrogen-sensitive substance, a large degree of heat generation in the presence of hydrogen could be obtained, and good stability was also achieved. A sensor device in which a column filled with the obtained catalyst powder was attached to a commercially available robust FBG for temperature measurement, and integrated with another FBG as a temperature reference via a heat shielding plate, was fabricated and evaluated. A stable baseline was demonstrated even in an environment where the ambient temperature severely fluctuated, and a sensor output proportional to the hydrogen concentration could be obtained. The detection limit was about 0.2 vol%, and the long-term stability of the device was good.

Effluents from the copper electrorefining as a secondary source of antimony: Role of mass transfer on the recovery by electrodeposition

The limited availability of antimony has increased the need for exploiting alternative sources to its direct extraction from stibnite deposits. Furthermore, introducing recovery techniques in industries where antimony is released in wastewaters leads to more responsible production routes. In this work, electrodeposition is employed to recover the antimony present in a secondary waste effluent of the copper electrorefining that is highly concentrated in hydrochloric acid. The electrochemical characterization of the system was conducted by voltammetry to identify a range of suitable operating conditions for the potentiostatic and galvanostatic electro-recovery of antimony. In potentiostatic mode, the progress of the secondary electrode reactions of hydrogen and chlorine evolution at potentials more cathodic than −0.38 V vs. Ag/AgCl causes the detachment and redissolution of the deposited antimony. Operating under galvanostatic control, similar effects were observed when the limiting current density is exceeded. Current efficiency and specific energy consumption values above 50 % and below 65 kW·h·kg−1, were achieved below the limiting current density (1.265 mA·cm−2). The operational range where electrodeposition of antimony is accelerated at increasing current densities can be broadened at intensified hydrodynamic conditions and higher concentrations of antimony. The detrimental effect of the hydrogen evolution reaction on the recovery of antimony decreases at high HCl concentrations.

Microscopic Diffusion of Atomic Hydrogen and Water in HER Catalyst MoS2 Revealed by Neutron Scattering.

The design of novel and abundant catalytic materials for electrolysis is crucial for reaching carbon neutrality of the global energy system. A deliberate approach to catalyst design requires both theoretical and experimental knowledge not only of the target reactions but also of the supplementary mechanisms affecting the catalytic activity. In this study, we focus on the interplay of hydrogen mobility and reactivity in the hydrogen evolution reaction catalyst MoS2. We have studied the diffusion of atomic hydrogen and water by means of neutron and X-ray photoelectron spectroscopies combined with classical molecular dynamics simulations. The observed interaction of water with single-crystal MoS2 shows the possibility of intercalation within volume defects, where it can access edge sites of the material. Our surface studies also demonstrate that atomic hydrogen can be inserted into MoS2, where it then occupies various adsorption sites, possibly favoring defect vicinities. The motion of H atoms parallel to the layers of MoS2 is fast with D ≈ 1 × 10-9 m2/s at room temperature and exhibits Brownian diffusion behavior with little dependence on temperature, i.e., with a very low diffusion activation barrier.

Triphenylphosphine assisted phosphorization of g-C3N4 for enhanced photocatalytic activity

It is an effective strategy to regulate the structure of photocatalysts for enhanced photocatalytic hydrogen evolution. In this work, a facile method was developed to introduce P atoms into g-C3N4via the thermal calcination treatment. In contrast to pristine g-C3N4, the obtained P-CN(PPh3) exhibited a negative shift of conduction band edge with enhanced light absorption after the introduction of P atoms into g-C3N4, thus benefiting the photocatalytic hydrogen evolution. Moreover, the introduction of P element in g-C3N4 can also improve the charge separation during the photocatalytic hydrogen reaction, significantly accelerating the photocatalytic hydrogen production rate of P-CN(PPh3).

Surface Cleaning and Modification of Oxide Films by Atomic Hydrogen Annealing

To suppress degradation of the electrical property of field-effect transistors, the removal of C contamination without damaging oxide films is important in the semiconductor industry. In addition, to reduce bonding failure, it is necessary to remove native oxide films from metal films. To achieve this, atomic hydrogen was generated by the decomposition of H2 gas on a heated tungsten mesh. This surface treatment is referred to as atomic hydrogen annealing (AHA). The reaction of atomic hydrogen with various oxide films, such as AlOx, TiOx, CrOx, NiOx, CuOx, and SiOx, was investigated. The O concentrations in Al, Ti, and Cr slightly decreased by AHA. The thermal oxide films prepared at 400 ℃ were not changed by AHA, except for CuOx. The reduction in the reactivity of the oxide film due to atomic hydrogen depends on the metal–oxygen bond strength. In addition, although the thermal oxide film of the Si substrate prepared at 1000 ℃ was not etched, AHA resulted in the etching of the Si-rich SiOx. These findings are useful for the removal of C contamination and native oxide films and for controlling the surface properties of oxide films.

Rethinking “BLEVE explosion” after liquid hydrogen storage tank rupture in a fire

The underlying physical mechanisms leading to the generation of blast waves after liquid hydrogen (LH2) storage tank rupture in a fire are not yet fully understood. This makes it difficult to develop predictive models and validate them against a very limited number of experiments. This study aims at the development of a CFD model able to predict maximum pressure in the blast wave after the LH2 storage tank rupture in a fire. The performed critical review of previous works and the thorough numerical analysis of BMW experiments (LH2 storage pressure in the range 2.0–11.3 bar abs) allowed us to conclude that the maximum pressure in the blast wave is generated by gaseous phase starting shock enhanced by combustion reaction of hydrogen at the contact surface with heated by the shock air. The boiling liquid expanding vapour explosion (BLEVE) pressure peak follows the gaseous phase blast and is smaller in amplitude. The CFD model validated recently against high-pressure hydrogen storage tank rupture in fire experiments is essentially updated in this study to account for cryogenic conditions of LH2 storage. The simulation results provided insight into the blast wave and combustion dynamics, demonstrating that combustion at the contact surface contributes significantly to the generated blast wave, increasing the overpressure at 3 m from the tank up to 5 times. The developed CFD model can be used as a contemporary tool for hydrogen safety engineering, e.g. for assessment of hazard distances from LH2 storage.

Generator for Large Fluxes of Kaons and Pions Using Laser-Induced Nuclear Processes in Ultra-Dense Hydrogen H(0)

Laser-induced nuclear reactions in ultra-dense hydrogen H(0) produce mesons with both relatively low kinetic energy and with high kinetic energy. The kaons have up to 100 MeV of kinetic energy, thus a velocity of 0.55 c. Each laser pulse of >0.1 J of energy and length of 5 ns produces 1013 mesons. The operation of the meson generator is here demonstrated by measuring all decay times for mesons in the ns range after induction by a pulsed laser. These decay times are the unique fingerprints of the mesons, and they also produce the kinetic energy of the mesons created from their time-dilated decay. The charged pion decay time at rest from this generator is measured to be 25.92 ± 0.04 ns (standard fit error), in reasonable agreement with the tabulated results of 26.033 ns. A similar accuracy is found for the other mesons as for the charged kaons, with 96 MeV of kinetic energy, at 14.81 ± 0.05 ns. The same general behaviour is found with both deuterium and normal hydrogen forming the ultra-dense phase H(0) on the laser target. This meson generator gives intense meson showers useful for many types of particle physics experiments at a small fraction of the cost of using particle accelerators. A particle accelerator would need an energy of at least 1021 eV to produce a similar shower of 1013 mesons. Thus, the described generator is among the most intense meson sources that exist. Other important applications include nuclear energy generation and particle (pion) radiation for cancer treatment.