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Quantum chemistry calculations using a reasonably simplified char model were performed to clarify the mechanisms of hydrogen iodide (HI) decomposition over carbon materials. The density functional theory at the B3LYP/3-21G** level was used to optimize the geometries of the reactants, products, stable intermediates, and transition states in possible reaction pathways. The main elementary reactions of the homogeneous decomposition of HI were simulated to verify the applicability of the chosen calculation method and basis set. The adsorptions of HI on two prototypical model chars were all irreversible chemisorption reactions. The results revealed that HI chemisorption preferentially occurred in the zigzag model compared with the energy barriers. Based on the chemisorption results, the decomposition process of HI in the zigzag model was calculated at the same level. The process of HI decomposition on carbon materials took place not directly but by a series of chemisorption and desorption reactions, which demonstrated that the desorption of I 2 and H 2 controls overall catalysis reaction. The initial carbon structure disappeared and turned into the iodine absorbed structure, which played a real catalytic role in the overall process. The two structures were compared by analyzing their electrostatic potentials (ESPs), which demonstrated that the iodine absorbed structure presented a higher activity than the initial carbon structure. A detailed mechanism of the catalytic decomposition of HI over the carbon materials was proposed based on the pathways that we obtained from the calculation results.

Sulfur-iodine thermochemical cycle is considered as a promising route for hydrogen production without CO2 emission. In this cycle, the hydrogen iodide conversion rate plays an important role in the total thermal efficiency to some extent. To improve the efficiency of HI decomposition, the homemade carbon membranes supported by α-alumina porous tubes were well-designed in a specific way and evaluated aiming at removing H2 from HI decomposition reaction side. Permeability, selectivity and stability of self-designed carbon membranes are investigated in some gaseous components in the present work. Firstly, single-component (H2/Ar) permeance was observed with differential pressure ranging from 0.05 to 0.2 Mpa. The result shows that differential pressure has little effect on H2 and Ar permeance. Secondly, the hydrogen and argon permeance through carbon membrane is 3.1 × 10−8 mol m−2 s−1 Pa−1 and 5.7 × 10−10 mol m−2 s−1 Pa−1 respectively at 300 °C. The separation factor of H2 and Ar is 54, which is greater than the theoretical value calculated by Knudsen diffusion equation. Thirdly, hydrogen permeability in the H2 HI H2O gaseous mixture system owns nearly the same as that of the single-component (H2) at 300–500 °C. Due to the large molecule diameter, most of HI are stopped by carbon membrane. However, H2O molecules could pass through the carbon membrane obviously. The permselectivity of H2/HI is over 310 at 500 °C. Last, after 10 h of stability tests, some slight damage are observed on the surface of carbon membrane according to the scanning electron micrograph (SEM). The structure change of carbon membrane gave rise to a little increase of H2 permeance at 20–100 °C.

The addition of hydrogen iodide to organometal halide perovskite precursor solution at 1% by volume leads to a significant enhancement in average power conversion efficiency (PCE) in inverted solar cell devices, increasing from 7.7% to 11.9% and 6.1% to 10.0% in spin-cast and spray-cast devices respectively. We directly attribute this improved device performance to increased thin-film surface coverage coupled with higher optical density. X-ray diffraction studies also reveal that the HI additive facilitates full conversion of the precursor material to the crystalline perovskite phase. From solution studies, we relate these changes in device performance to the presence and distribution of precursor aggregates that effectively pattern the formation of perovskite crystals during film formation.

Bimetallic Ni-Pt nanoparticles supported on four different supports (activated carbon (AC)), γ-alumina, zirconia, and ceria) were prepared by modified impregnation-reduction technique for decomposition of hydrogen iodide to hydrogen and iodine, in the thermochemical water-splitting sulfur-iodine (SI) cycle. The catalysts were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) method to find their structure, morphology, and surface area, respectively. High metal dispersions (Ni-Pt) were obtained with particle sizes of the order of 10 nm or lesser, in the high-surface-area supports. The hydrogen iodide-decomposition results showed catalytic activity of Ni-Pt nanoparticles in the following order on different supports: Ni(2.5%)-Pt(2.5%)/AC > Ni(2.5%)-Pt(2.5%)/γ-alumina > Ni(2.5%)-Pt(2.5%)/Zirconia > Ni(2.5%)-Pt(2.5%)/Ceria. Bimetallic Ni(2.5%)-Pt(2.5%)/AC also showed excellent stability for 100 h in the hydrogen iodide-decomposition reaction, and with a higher performance relative to the corresponding Pt supported catalyst under the same operating conditions.

Sulfur-Iodine thermochemical cycle process has been considered a promising method to generate hydrogen from water. One of the main limitations of this process lies in the hydrogen iodide decomposer section, which requires substantial amount of heat at high temperature. The present study analyses the heat transfer limitation effect on the performance of hydrogen iodide decomposition in a multi-tubular catalytic reactor by means of dynamic simulation. The extensive numerical simulation shows that the inlet temperature heating medium (Helium gas) should be at least 700°C so to enable at least 90% conversion when the inlet molar fraction of hydrogen iodide is 0.6. Lowering the inlet heating medium will require the reduction in the inlet molar fraction of hydrogen iodide in order to keep the conversion at 90% and above.

In this work, Pt/TiO2 catalysts were synthesized by a simple sol-gel method at different calcination temperatures. TEM study revealed 5 nm particles of Pt/TiO2 calcined at 400 °C. BET surface area ...

Thin film CdTe solar cells were prepared using close-space sublimation followed by a standard cadmium chloride activation annealing treatment. After the activation process, some of the samples were subjected to a brief etching process using a 10% hydrogen iodide solution in methanol while the others were only rinsed with methanol. Completed solar cells from both sample types were prepared and characterized using current and capacitance-voltage scanning methods. The results show that the etching process increases the open circuit voltage by 10-20mV and the fill factor by 1-5% compared to the devices without the etching, thus increasing the efficiency from $\sim$ 13% to $\sim$ 15%. Capacitance-voltage measurements indicate that the bulk carrier (hole) density of the CdTe films increase by approximately a factor of three, which could partially explain the increase in device performance. The cause of the change in carrier density is still under investigation.

The solvent-free reaction of 1-iodomethyl-1,1,3,3,3-pentamethyldisiloxane with 1,2,4-triazole derivatives and 1,2,3-benzotriazole afforded organylcyclosiloxane iodides and triiodides. The reactions involved alkylation of pyridine and pyrrole nitrogens and cleavage of the siloxane bonds mediated by hydrogen iodide generated upon the reaction.

The operating characteristics of hydrogen iodide (HI) decomposition for hydrogen production were investigated using the commercial computational fluid dynamics code, and various factors, such as hydrogen production, heat of reaction, and temperature distribution, were studied to compare device performance with that expected for device development. Hydrogen production increased with an increase of the surface-to-volume (STV) ratio. With an increase of hydrogen production, the reaction heat increased. The internal pressure and velocity of the HI decomposer were estimated through pressure drop and reducing velocity from the preheating zone. The mass of H2O was independent of the STV ratio, whereas that of HI decreased with increasing STV ratio.

A novel phosphorus-containing porous polymer is efficiently prepared from tris(4-vinylphenyl)phosphane by radical polymerization, and it can be easily ionized to form an ionic porous polymer after treatment with hydrogen iodide. Upon ionic exchange, transition-metal-containing anions, such as tetrathiomolybdate (MoS4 2−) and hexacyanoferrate (Fe(CN)6 3−), are successfully loaded into the framework of the porous polymer to replace the original iodide anions, resulting in a polymer framework containing complex anions (termed HT-Met, where Met = Mo or Fe). After pyrolysis under a hydrogen atmosphere, the HT-Met materials are efficiently converted at a large scale to metal-phosphide-containing porous carbons (denoted as MetP@PC, where again Met = Mo or Fe). This approach provides a convenient pathway to the controlled preparation of metal-phosphide-loaded porous carbon composites. The MetP@PC composites exhibit superior electrocatalytic activity for the hydrogen evolution reaction (HER) under acidic conditions. In particular, MoP@PC with a low loading of 0.24 mg cm−2 (on a glass carbon electrode) affords an iR-corrected (where i is current and R is resistance) current density of up to 10 mA cm−2 at 51 mV versus the reversible hydrogen electrode and a very low Tafel slope of 45 mV dec−1, in rotating disk measurements under saturated N2 conditions.

Regioselective synthesis of 1,2,3-triazoles with ferrocenyl moieties in positions 1, 4, and 5 was carried out in a two-step reaction sequence: a copper-mediated azide–alkyne cycloaddition followed by a palladium-catalyzed cross-coupling. A new route towards 5-iodo-1,2,3-triazoles was developed using N-iodomorpholine hydrogen iodide, instead of the corrosive and toxic ICl, as the I+ source. The novel methodology together with a consecutive Suzuki or Sonogashira reaction was shown to be a useful procedure for the synthesis of a wide range of ferrocenyl 1,2,3-triazoles with di- and triferrocenyl derivatives among them.

This study examines four carbon materials through a series of characterization methods and a hydrogen iodide (HI) decomposition test. Applying a traditional structure to carbon materials facilitates the quantitative analysis of the four samples. The X-ray diffraction and Raman spectroscopy results indicate that lesser stacked graphite-like layers and shorter lateral diameter La result in higher disordering structure. However, the quantity of active sites is not determined only by the degree of disordering. The aliphatic carbon in the inter-layer correlations decreases the amount of graphite carbon and occupies its edge, thereby inhibiting the formation of edge sites in carbon materials. A low ratio of amorphous carbon with a high degree of disordering corresponds to a high concentration of surface active sites associated with the edges of graphite-like layers. The catalytic performance combined with characterization results demonstrates that the edges of graphite carbon are active sites in HI decomposition. A computational chemistry study is also conducted to illustrate the dominant role of edge sites in the reaction. The calculation results build a detailed mechanism of the catalytic decomposition of HI over the carbon materials and verify that the adsorbed I on the edge sites facilitate the HI decomposition.

This study aimed to determine the influence of Ir content on the behavior of Pt-Ir/C catalysts for hydrogen iodide decomposition in iodine–sulfur thermochemical water-splitting cycle. A series of bimetallic x Pt- y Ir/C catalysts ( x = 4, 3, 2.5, 2, 1 wt.%; y = 1, 2, 2.5, 3, 4 wt.%) were prepared by co-impregnation and reduction method. For comparison, monometallic 5%Pt/C and 5%Ir/C catalysts were also prepared. The catalysts were characterized by X-ray diffraction and transmission electron microscopy. Changing the Ir content in the bimetallic Pt-Ir/C catalysts can modify the particle size and dispersion state of the supported metal nanoparticles. The results of the characterizations of the fresh and used catalysts indicated that the size of the Pt nanoparticles has significantly increased after HI decomposition whereas that of the Pt-Ir nanoparticles is more resistant to particle growth. Among the Pt, Ir, and binary Pt-Ir catalysts, the bimetallic 2.5%Pt-2.5%Ir/C exhibited the highest catalytic activity toward HI decomposition. The 70 h durability test showed that the Pt-Ir bimetallic catalyst possessed good activity maintenance.

Equilibrium conditions of the main reactions of the SI cycle were studied in this paper. The extent of reaction for two main reactions of this cycle including sulfuric acid decomposition and hydrogen iodide decomposition was evaluated as a function of temperature, pressure, and initial mole number of reactants. In the reaction modelling of sulfuric acid and sulfur trioxide decompositions, two models including simple and multiple reaction models were considered. In the simple model, it was assumed that two decomposition reactions proceeded independently. However, in the multiple reaction model, both reactions were considered simultamneously. It was shown that the Bunsen reaction completely proceeded in the range of operating conditions of the Bunsen reactor. Also, sulfuric acid was demonstrated to be decomposed at a higher rate when the reaction temperature and initial concentration of the sulfuric acid and sulfur trioxide increased. Furthermore, the operating pressure had to be maintained at lower values and the generated sulfur dioxide had to be withdrawn from the reactor in order to have a higher yield of product in this reactor. Finally, in the hydrogen iodide decomposition, the operating pressure, temperature, and concentration of hydrogen iodide had to be maintained at higher values to have a complete reaction. Moreover, the generated hydrogen was shown to be withdrawn from the hydrogen iodide reactor to prevent from backward reaction.

One of the more well-known examples of thermochemical water splitting cycles is the sulfur–iodine cycle, which utilizes iodine and sulfur dioxide to transform water into hydrogen and oxygen. A novel sulfur–sulfur cycle has been developed based on the original sulfur–iodine cycle, seeking an overall more favorable chemical process. The initial stages of the original and novel cycles are the same, in using sulfur dioxide and iodine with an excess of water to form two strong acids, hydrogen iodide and sulfuric acid. The secondary reactions differ greatly and are based on a previously unwanted side reaction where the two strong acids regenerate iodine and water along with hydrogen sulfide, as shown in the equations below. The hydrogen sulfide can then be steam reformed to hydrogen and sulfur dioxide, completing the cycle. Excess sulfuric acid can also be treated to regenerate water and sulfur dioxide. I 2 ( l ) + S O 2 ( g ) + 2 H 2 O ( l ) → 2 H I ( l ) + H 2 S O 4 ( l ) 8 H I ( l ) + H 2 S O 4 ( l ) → 4 I 2 ( l ) + 4 H 2 O ( l ) + H 2 S ( g ) This study seeks to explore the reaction kinetics of this two-step reaction by altering the various reaction temperatures and the initial concentration of water and to develop a robust and simple predictive model based on the resulting experimental data. The results suggest that an increase in the initial concentration of water will increase the rate of both reactions substantially and that it is beneficial to carry them out in the same vessel. A predictive model was successfully developed that allows for monitoring the progression of iodine through the reaction system in a batch setting. The results of the experimental and modeling work warrants further development of this novel sulfur–sulfur thermochemical water splitting cycle.

Progress toward the total syntheses of a diverse set of fawcettimine-type Lycopodium alkaloids via a "Heathcock-type" 6-5-9 tricycle is disclosed. This route features an intermolecular Diels-Alder cycloaddition to rapidly furnish the 6-5-fused bicycle and a highly chemoselective directed hydrogenation to build the azonane fragment. While conducting these synthetic studies, trimethylsilyl iodide was found to effect a hydroamination reaction to furnish the tetracyclic core of serratine and related natural products. This observation has been expanded into a general method for the room temperature hydroamination of unactivated olefins with tosylamides utilizing catalytic "anhydrous" HI (generated in situ from trimethylsilyl iodide and water). The presence of the iodide anion is critical to the success of this Brønsted acid catalyzed protocol, possibly due to its function as a weakly coordinating anion. These conditions also effect the analogous hydroetherification reaction of alcohols with unactivated olefins.

Conversion of tantalum alloy scrap into high-value, electronic-grade tantalum nanopowders is a significant economic and technological advancement. At present, it is only possible to recycle tantalum alloy scrap into low-value tantalum mill products; however, upgrading this metal stream into the raw materials for the capacitor industry offers economic payback and environmental savings. A new technology platform based on the iodization of tantalum alloy scrap produces volatile tantalum(V) iodides that can be condescended to form fine powders. Subsequent hydrogen reduction of the iodide powders in a plasma furnace produces high surface area tantalum metal powder precursors, which, after annealing, yield high-purity nanopowders with uniform particle size distribution, low oxygen content, and high surface area and capacitance. The hydrogen iodide produced during plasma reduction can be captured, dissociated into molecular hydrogen and molecular iodine, and recycled. The total process flow sheet is presented.

Physical review / B 96(14), 144105 (2017). doi:10.1103/PhysRevB.96.144105, Through high-pressure Raman spectroscopy and x-ray diffraction experiments, we have investigated the formation, stability field, and structure of hydrogen iodide (HI). Hydrogen iodide is synthesized by the reaction of molecular hydrogen and iodine at room temperature and at a pressure of 0.2 GPa. Upon compression, HI solidifies into cubic phase I, and we present evidence for the emergence of a phase I′ above 3.8 GPa. Across the wide temperature regime presented here, HI is unstable under compression (11 GPa at 300 K, 18 GPa at 77 K), decomposing into its constituent elements, after which no further reaction between hydrogen and iodine was observed up to pressures of 60 GPa. This study provides both the constraints on the phase diagram of HI and its kinetic stability, Published by APS, Woodbury, NY

Traditional electron-transfer dissociation (ETD) experiments operate through a complex combination of hydrogen abundant and hydrogen deficient fragmentation pathways, yielding c and z ions, side-chain losses, and disulfide bond scission. Herein, a novel dissociation pathway is reported, yielding homolytic cleavage of carbon-iodine bonds via electronic excitation. This observation is very similar to photodissociation experiments where homolytic cleavage of carbon-iodine bonds has been utilized previously, but ETD activation can be performed without addition of a laser to the mass spectrometer. Both loss of iodine and loss of hydrogen iodide are observed, with the abundance of the latter product being greatly enhanced for some peptides after additional collisional activation. These observations suggest a novel ETD fragmentation pathway involving temporary storage of the electron in a charge-reduced arginine side chain. Subsequent collisional activation of the peptide radical produced by loss of HI yields spectra dominated by radical-directed dissociation, which can be usefully employed for identification of peptide isomers, including epimers. Graphical Abstract ᅟ.

The new reaction of terminal alkynes with iodogermanes proceeding in the presence of an Ir(I)-complex [{Ir(μ-Cl)(CO)2}2] (I) and NEt((i)Pr)2, as a hydrogen iodide acceptor, leads to the formation of functionalized alkynylgermanes. This reaction occurs via direct activation of the C(sp)-H bond in the starting alkyne. Detailed stoichiometric experiments using [Ir(cod)(CCPh)(PCy3)] (IVa) and iodogermane were performed and resulted in a proposal of a reasonable mechanism for the germylative coupling reaction between alkynes and iodogermanes.

Numerical simulations to develop an understanding of transport processes inside PBMRs (packed bed membrane reactors) and to evaluate effectiveness of PBMRs in increasing the conversion of HI (hydrogen iodide) decomposition reaction of IS (iodine–sulfur) thermochemical cycle are reported. The computational approach used in the simulations has been validated using the data reported for HI decomposition in a packed bed reactor (PBR). The validated computational approach has been used for parametric studies. Effects of different parameters (temperature, pressure, space velocity, membrane permeability, permselectivity, packed bed porosity and reactor diameter) on HI conversion are reported. The parameters having the maximum impact on the conversion are identified. The findings show that using a PBMR instead of a PBR leads to significant enhancement in conversion and the parameters having high impact on conversion are wall temperature, feed temperature, reactor diameter and packed bed porosity. Based on the findings of parametric studies, ranges of the parameters having maximum impact on conversion are suggested, e.g. the reactor wall temperature is recommended to be in the range of 690–700 K, the bed porosity is recommended to be in the range of 0.2–0.4.

The DSC (Differential Scanning Calorimetry) analysis of heavy ozonized C60 fullerene (known also as “fullerene ozopolymer”), shows the exothermal decomposition of this compound with a peak at 158°C with a decomposition enthalpy ΔHdec ≈ −322 kJ/mol and an activation energy for the decomposition E# = 71 kJ/mol. These experimental facts confirm the secondary ozonide/peroxidic and polymeric nature of fullerene ozopolymer originally suggested by the infrared spectroscopy analysis and solid state 13C-NMR spectroscopy. It is also shown that the secondary ozonide group of fullerene ozopolymer can be reduced selectively by a treatment with hydrogen iodide.

The hydrogen iodide (HI) decomposition process is a limiting step for the efficiency of the sulfur–iodine nuclear hydrogen production process, owing to its low kinetics and complicated reaction characteristics. Therefore, the Korea Advanced Institute of Science and Technology (KAIST) suggested a simple high-temperature HI decomposition process at 650–700 °C for higher efficiency. For practical application of the high-temperature HI decomposition process, along with the catalyst study, we performed structure material selection and corrosion resistance tests. A number of candidate alloys were considered in various aspects and exposed to the high-temperature HI gas environment, which is extremely corrosive, at 850 °C for 100 h. Nine alloys with different nickel and iron compositions have been tested and analyzed. Test results indicated the degrees of resistances to corrosion of each alloy, on the basis of weight change and cross-sectional micrographs. Thus, because of their resistance to internal oxidation and formation of stable external oxide layers, five types of alloys, Haynes 214, aluminizing and inter-diffusion heat-treated or electron beam surface-treated Alloy 617 are suggested as appropriate candidates for fabricating high-temperature HI decomposer. In particular, surface-treatment of Alloy 617 gave it a high stability because of the resultant formation of an Al-rich layer; this was confirmed by experimental results, so IDHT Alloy 617 is recommended as a suitable structural material for fabricating HI decomposer. However, further long-term testing is suggested to ensure safety and confirm applicability.

In thermochemical water-splitting iodine–sulfur cycle, concentrating hydrogen iodine in the HI–H2O–I2 solution is crucial for the efficient hydrogen production. Electro-electrodialysis (EED) is a very promising HI concentrating method. In this paper, EED experiments were carried out using stacked cells, aiming at the scale up of EED equipment. Compared with the single-unit EED cell, the multi-cell EED stacks could concentrate HI in catholyte much more rapidly. During the EED process, the cell voltages increased gradually with the expansion of the concentration difference between catholyte and anolyte. For the stacks with more EED cells, the voltage increased much more steeply. High operating temperature ensured EED process carried out under low cell voltages and avoided voltage swelling. The apparent transport number (t+) of all the experiments were very close to 1, while the ratio of permeated quantities of water to H+ (β) changed in a range of 1.79–3.05, influenced by temperature, I2 content and current density.

In this paper, a series of bimetallic palladium–iridium catalysts supported on active carbon (Pd–Ir/C) were prepared by the impregnation-reduction method. Effects of the composition on the performance and stability of bimetallic catalysts in the decomposition of HI were investigated. X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) surface area were employed to characterize their structure, morphology and surface area, respectively. The results of activity tests indicated that all the bimetallic Pd–Ir catalysts were more active than the monometallic 5% Pd/C and 5% Ir/C catalysts at both 400 °C and 500 °C. Among Pd, Ir and binary Pd–Ir catalysts, the 4% Pd–1% Ir/C was the most active for HI catalytic decomposition at 400 °C. Due to the low cost, high activity and good stability, the carbon supported bimetallic Pd–Ir catalysts are more potential candidates to replace Pt/C for HI decomposition in the IS thermochemical cycle.

In this study, 5%Ni/Ce(1−x)ZrxO2( x = 0, 0.2, 0.5, 0.8, 1) catalysts were prepared by sol–gel method and tested for hydrogen iodide (HI) decomposition in sulfur–iodine (SI) cycle. The effects of zirconia incorporation were subsequently examined by a series of characterization methods. In comparison with the blank test, all of the catalysts, particularly Ni/Ce0.8Zr0.2O2, remarkably enhance the HI decomposition. Therefore, adding a small amount of zirconia results in the highest catalytic activity, which could be attributed to the following three effects: increase in oxygen mobility and oxygen vacancy, stronger interaction between NiO and the supports. The oxygen mobility and oxygen vacancy are dominant in the HI decomposition. The strong interaction between NiO and the supports accelerates the oxygen transfer from the bulk to surface, which could also enhance the decomposition. However, excessive zirconia content has negative effects, which is due to the decrease in oxygen mobility and surface area. The poor thermal stability in zirconia-rich supports also restricts catalytic performance. In addition, a hypothetic mechanism of HI catalytic decomposition over Ni/Ce(1−x)ZrxO2 is proposed.

The ice quasi-liquid layer (QLL) forms on ice surfaces below the bulk ice melting temperature. It is abundant in the atmosphere, and its importance for atmospheric chemistry is recognized. In the present work, we have studied the microscopic mechanisms of acid ionization on the QLL using ab initio molecular dynamics. The model system QLL is established by nanosecond time scale simulations with empirical force fields, while the reactivity of the QLL is studied using ab initio molecular dynamics. Our ab initio simulations reveal that QLL is reactive, exhibiting stable crystalline point defects, which contribute to efficient acid solvation, ionization, and proton transfer. We study in detail deuterated hydrogen iodide (DI) and nitric acid (DNO3). Ionization in both cases benefits from the abundance of weakly bonded hydrogen-bond single-acceptor double-donor water molecular species available on the QLL in high relative concentration. Picosecond time scale ionization is demonstrated for both molecular species. Our results suggest efficient reactivity of acid ionization and proton transfer at temperature ranges appropriate for the upper troposphere and lower stratosphere.

We propose a hybrid HI decomposer, which combines a high-temperature catalytic decomposition reactor with a dual bed temperature-swing decomposer. For the high temperature step, we screened and identified a catalyst that is stable above 700 °C by preparing nickel catalysts supported on mesoporous alumina and evaluating their activity toward the high-temperature catalytic decomposition reaction. The catalysts achieved HI decomposition yields up to 23% at 650 °C and maintained over 20% yield after 100 h of operation. For the temperature-swing process, we investigated the adsorption, desorption, and regeneration efficiency, and the optimal regeneration temperature of nickel catalysts supported on silica/alumina adsorbents. The optimal regeneration temperature was 400 °C. Based on these results, we propose hybrid HI decomposers in two configurations: 1) residual HI decomposer and 2) HI concentrator. The residual HI decomposer improves the overall conversion efficiency to levels above the thermodynamic limit, while the HI concentrator increases the concentration of HI by simple temperature control, even at below-azeotropic HI concentrations.

This review article presents and discusses the recent progress made in the stabilization, protection, improvement, and design of halide perovskite‐based photocatalysts, photoelectrodes, and devices for solar‐to‐chemical fuel conversion. With the target of water splitting, hydrogen iodide splitting, and CO2 reduction reactions, the strategies established for halide perovskites used in photocatalytic particle‐suspension systems, photoelectrode thin‐film systems, and photovoltaic‐(photo)electrocatalysis tandem systems are organized and introduced. Moreover, recent achievements in discovering new and stable halide perovskite materials, developing protective and functional shells and layers, designing proper reaction solution systems, and tandem device configurations are emphasized and discussed. Perspectives on the future design of halide perovskite materials and devices for solar‐to‐chemical fuel conversion are provided. This review may serve as a guide for researchers interested in utilizing halide perovskite materials for solar‐to‐chemical fuel conversion.

Electro-electrodialysis (EED) has been applied to the thermochemical water-splitting iodine-sulfur process for hydrogen production to enhance the hydrogen iodide (HI) component in the HI–I2–H2O mixture (HIx solution). In this work, the HIx solution concentration dependence of conductivity and transport number as the membrane-performance indexes of Nafion 212 and a styrene-grafted poly(ethylene-co-tetrafluoroethylene) (ETFE) membrane was investigated experimentally. From a theoretical analysis of measurements based on the new EED model, the effects of the H+ and I− contents and the diffusion coefficients of H+ and I− in the evaluated membranes on conductivity and transport number were as follows: HIx solution concentration dependence of the H+ and I− contents exhibited a significantly small or different variation in comparison with that of conductivity and transport number, indicating that the dominant factors for conductivity and transport number would not be the H+ and I− contents; thereby, the effect of the diffusion coefficients of H+ and I− should not be ruled out. In terms of the conductivity of Nafion 212, the diffusion coefficient of H+ is the dominant factor because the existence of I− was negligible, whereas in the case of the ETFE-St membrane, the effect of the diffusion coefficient of I− should be considered. The diffusion coefficient of I− could more strongly affect transport number for the evaluated membranes rather than the diffusion coefficient of H+, indicating that the H+ selectivity of the membranes could be determined relatively based on variations of I− behavior in the membranes.

In this work, the decomposition of hydrogen iodide (HI) over platinum catalyst in a frame work of the development of a bench-scale Sulfur–Iodine (S–I) cycle is studied. The catalyst Pt/γ-alumina 1.0 wt% is prepared by impregnation–calcination method. The experiments of HI decomposition over the as-prepared catalyst are conducted at the temperature range of 350–550 °C and at the atmospheric pressure. The experimental data are then used to estimate new kinetic parameters for HI decomposition on the basis of Langmuir–Hinshelwood type where the surface reaction is considered as the rate-limiting step. The kinetics with the estimated parameters shows a reasonable agreement with the experimental data. It also reflects the fact that, HI conversion is significantly decreased with a small amount of iodine present in the feeding solution. Thereafter, the kinetic model is applied to the modeling of a HI decomposer for the hydrogen production rate of 1 Nm 3 /h in which hot helium gas is used to provide heat for the decomposition. Effects of heat-exchanger reactor configuration and composition of the feeding solution on the reactor size and the heat consumed are examined using the proposed model. Calculation results show that heat consumed for the co-current configuration is less than that for the counter-current configuration of the reactor. I 2 impurity and high water content in the feeding solution also result in an increase of reactor size and the heat required.

Coal-based activated carbon (AC-COAL) catalysts subjected to acid treatment were tested to evaluate their performance on hydrogen-iodide (HI) decomposition for hydrogen production in sulfur-iodine (SI or IS) cycle. The effects of acid treatment on catalysts and the relations between sample properties and catalytic activities were discussed. The AC-COAL obtained by non-oxidative acid treatments had the best catalytic activity. However, the catalytic activity of AC-COAL decreased after the treatment of nitric acid. Higher surface area, higher carbon contents, lower ash contents and fewer surface oxidation groups contributed to the catalytic activity of ACs. HI decomposition on the AC surface itself may be due to high densities of unpaired electrons associated with structural defects and edge plane sites with similar structural ordering. Moreover, the oxygen-containing groups reduced the electron transfer capability associated with the basal plane sites.

This work is investigated for the catalytic decomposition of hydrogen iodide (HI). Platinum was used as active material by loading on ZrO2-SiO2 mixed oxide in HI decomposition reaction. To obtain high and stable conversion of hydrogen iodide in severe condition, it was required to improve catalytic activity. For this reason, a method increasing dispersion of platinum was proposed in this study. In order to get high dispersion of platinum, zirconia was incorporated in silica by sol-gel synthesis. Incorporating zirconia influence increasing platinum dispersion and BET surface area as well as decreasing deactivation of catalysts. It should be able to stably product hydrogen for a long time because of inhibitive deactivation. HI decomposition reaction was carried out under the condition of 450℃ and 1 atm in a fixed bed reactor. Catalysts analysis methods such as N2 adsorption/desorption analysis, X-ray diffraction, X-ray fluorescence, ICP-AES and CO gas chemisorption were used to measurement of their physico-chemical properties.

Within DFT (B3LYP) methods the potential surface of the interaction between 1-iodopropan-2-one and 1,2,3-benzotriazole resulting in the formation of 1,3-bis(2-oxopropyl)-3H-1,2,3-benzotriazolium triiodide is studied. A mechanism consisting of four steps (N1-alkylation of 1,2,3-benzotriazole, elimination of molecular iodine during partial reduction of 1-iodopropan-2-one with hydrogen iodide, formation of the triiodide structure, and formation of 1,3-bis(2-oxopropyl)-3H-1,2,3-benzotriazolium) is proposed. Thermodynamic and kinetic parameters of these steps are obtained.

The catalytic decomposition of hydrogen iodide (HI) has drawn increasing attention because it is the key reaction for hydrogen production in the Iodine–sulfur (IS) thermochemical water splitting cycle, which is considered one of the most promising alternative methods for massive hydrogen production with high efficiency and without CO 2 emissions. Because it is very difficult for HI to decompose without the catalysts even at 500 °C, some catalysts have to be used to catalyze this reaction. In this study, four kinds of PtNi bimetallic catalysts supported on activated carbon (PtNi/C) were prepared by electroless plating and their catalytic activities were compared for HI decomposition in a fixed bed reactor at 400 and 500 °C under atmospheric pressure. Their differences in structures, surface areas, and morphology were characterized by XRD, BET and TEM, respectively. The used catalysts were also analyzed by TEM characterization in order to investigate the stability of catalysts. The results showed that the PtNi/C bimetallic catalysts are promising catalysts for HI decomposition because of their high activity and good stability, especially at high reaction temperature.

A model for the formation of hydrogen iodide gas directly in the channels of the first loop of a reactor during a serious accident initiated, by a source of radiation, in a mixture of vapors of fission products and water during radiative decay is described. The main parameters of the model are determined. It is shown that substantial conversion of cesium iodide vapor into hydrogen iodide is possible.

A series of binary Pd–Pt catalysts supported on active carbon were prepared by the co-impregnation and reduction method. For comparison, active carbon supported monometallic Pt and Pd catalysts were also prepared by the impregnation–reduction method. Their structure, morphology and surface area were investigated by means of X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) surface area, respectively. Their catalytic activities were evaluated for the decomposition of hydrogen iodide (HI). Furthermore, their thermal stabilities were also investigated. The results of activity tests showed that the composition of Pd–Pt binary catalysts played the important role in dictating the catalyst activity. Among the Pt, Pd and binary Pd–Pt catalysts, the 2.5%Pd–2.5%Pt/C showed the best catalytic performance for the decomposition of HI. The results of thermal stability tests showed that the binary Pd–Pt catalyst had the higher stability than the monometallic Pt and Pd catalysts.