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Over the recent past, lead-based halide perovskite materials have drawn significant attention due to their excellent optical and electrical properties for solar cells and optoelectronics applications. However, the toxicity of lead elements and instability under ambient conditions leads to develop alternative compositions. Herein, we report a novel mechanochemical synthesis of tin iodide-based double perovskites (A2SnI6; A = Rb+, Cs+, methylammonium, and formamidinium), and their structural, optical, and electrical properties are investigated. Importantly, we found that the hydrogen iodide (HI) addition during the ball-milling process minimizes secondary phase formation in the synthesized A2SnI6 powders. The effects of HI addition and the A-site substitution are investigated with respect to the lattice parameters, optical bandgaps, and electrical properties of the synthesized perovskite materials. Our results demonstrate essential information to improve the understanding of halide perovskite materials and develop efficient lead-free perovskite photoelectric devices.

In this study, a corrosion-stable silica membrane was developed to be used in H2 purification during the hydrogen iodide decomposition (2HI → H2 + I2), which is a new application of the silica membranes. From a practical perspective, the membrane separation length was enlarged up to 400 mm and one end of the membrane tubes was closed to avoid any thermal variation along the membrane length and sealing issues. The silica membranes consisted of a three-layer structure comprising a porous α-Al2O3 ceramic support, an intermediate layer, and a top silica layer. The intermediate layer was composed of γ-Al2O3 or silica, and the top silica layer that is H2 selective was prepared via counter-diffusion chemical vapor deposition of a hexyltrimethoxysilane. To the best of our knowledge, this is the first report of 400-mm-long closed-end silica membranes supported on Si-formed α-Al2O3 tubes produced via chemical vapor deposition method. A 400-mm-long closed-end membrane using a Si-formed α-Al2O3 tube exhibited a higher H2/SF6 selectivity of 1240 but lower H2 permeance of 1.4 × 10−7 mol Pa−1 m−2 s−1 with compared with the membrane using a γ-Al2O3-formed α-Al2O3 tube (907 and 5.6 × 10−7 mol Pa−1 m−2 s−1, respectively). The membrane using the Si-formed α-Al2O3 tube was more stable in corrosive HI gas than a membrane with a γ-Al2O3-formed α-Al2O3 tube after 300 h of stability tests. In conclusion, the developed silica membranes using the Si-formed α-Al2O3 tubes seem suitable for membrane reactors that produce H2 on large scale using HI decomposition in the thermochemical iodine–sulfur process.

CsPbI3 triggers strong interest in the photovoltaic community for their promising photoelectric property and nonvolatility. However, CsPbI3 layers with a-phase crystal structure are difficult for preparation, and these layers easily degrade to non-photoactive δ-phase at room temperature. Tuning the composition of precursor solutions is an important method for improving the properties of CsPbI3 layers. Herein, we prepare inorganic a-CsPbI3 perovskite solar cells using lead acetate as the lead source, which is different from conventional precursors with lead iodide as the lead source. The lead acetate precursor needs neither incorporating hydrogen iodide nor preparing PbI2 complex, and it is shown to enlarge the grain size, improve the crystallinity and reduce the trap density of CsPbI3 layers. By cooperating the lead acetate precursor with EDAI2 additive, the power conversion efficiency (PCE) of devices increases from 9.2% to 12.9% and the photo-stability of these devices is improved simultaneously.

A thermochemical water-splitting iodine–sulfur process offers the potential for mass-producing hydrogen at high-efficiency levels, and it uses high-temperature heat sources, including high-temperature gas-cooled reactors, solar heat, and waste heat of industries. The raw material (H2O) is split into H2 and O2 by combining three chemical reactions using sulfur and iodine. Currently, R&D tasks are essential to confirm the integrity of the components that are made of practical structural materials and the stability of hydrogen production in harsh working conditions. A test facility for producing hydrogen was constructed from corrosion-resistant components that are developed using industrial materials. In addition, for stable hydrogen production, technical issues for instrumental improvements (i.e., stable pumping of the hydrogen iodide (HI)–I2–H2O solution without locking the shaft seal, prevention of leakage by improving the quality control of glass-lined steel, prevention of I2 precipitation using a water removal technique in a Bunsen reactor) were solved. The entire process was successfully operated for 150 h at the rate of ca. 30 L/h. The integrity of components made of practical structural materials and the operational stability of the hydrogen production facility in harsh working conditions were demonstrated.

Using simple and efficient methods to synthesize biological activated carbon catalysts (ACCs) with the decomposition of hydrogen iodide (HI) in the sulfur-iodine cycle as a typical reaction is urgently needed for the commercialization of hydrogen energy production and development. In this study, a series of ACCs with different specific surface areas (SSAs) and pore structures are prepared by comparing and controlling the changes in carbonization and activation methods of activated carbon (AC) preparation process. Hierarchical porous AC with larger SSA has higher HI decomposition efficiency. The representative samples H240H1h and H240C4h are hierarchical porous ACCs with 48.96% and 46.88% micropores, respectively, and have the highest catalytic activity in the entire series. The nitrogen adsorption and desorption curve is combined with pore size distribution data and analyzed using the capillary aggregation (Kelvin) and monolayer adsorption (Langmuir) theories. And ACC pore grading coefficient—which can improve data visualization—is introduced.

The first example of a palladium-catalyzed oxidative carbonylative S-cyclization process carried out under aerobic conditions is reported. The method is based on the use of the PdI2/KI catalytic system and an acetylenic substrate bearing a sulfurated group in suitable position for attacking the coordinated triple bond. To avoid the possible oxidation of a free thiol group, a methylthio group was used as sulfur nucleophile, since the methyl group on sulfur could be removed under the reaction conditions by reaction with the iodide anion to give methyl iodide. In particular, we have employed as substrates 1-(methylthio)-3-yn-2-ols, which, upon S-cyclization, demethylation, and alkoxycarbonylation, led to thiophene-3-carboxylic esters in one step, in alcohols as external nucleophile and solvents, and under 40 atm of a 4:1 mixture of CO-air (air being the source of oxygen, used as external oxidant). The Pd(0) species deriving from the alkoxycarbonylation process was reoxidized back to catalytically active PdI2 by the action of oxygen in combination with the hydrogen iodide ensuing from the alkoxycarbonylation step and from water attack to methyl iodide. This new synthetic transformation could be successfully applied to a variety of differently substituted 1-(methylthio)-3-yn-2-ols, including substrates bearing geminal dialkyl substituents.

A series of N-doped activated carbon (NAC) with varying N contents were prepared to study the effect of N-doping on hydrogen iodide (HI) decomposition over activated carbon in sulfur-iodine (SI) cycle for hydrogen production. Element analysis, XPS and N2 adsorption were performed for samples’ characterization. The HI conversion was proportional to the N content and the sample with 6.006% N content gave the highest HI conversion of 22.84%. Density functional theory (DFT) calculations confirmed the experimental results and elucidated the influence mechanism. The increase of N contents was favor to the decomposition of HI by enhancing the chemisorption of HI molecule on carbon structure. The role of N-doping was to remodel the local electronic density and charge distribution on the carbon surface. In addition, the effect of types of N-containing functional groups on HI decomposition was calculated. Results showed that the N-6 structure was conducive to the chemisorption of HI but N-5 and N-Q structures had a reverse effect. However, when the three N-containing functional groups exist simultaneously, the overall chemisorption of HI was enhanced, which, in turn, enhanced the decomposition of HI. This study can provide underlying guidance for preparing highly efficient NAC for HI decomposition.

In this study, the catalytic decomposition of hydrogen iodide was theoretically and experimentally investigated in a silica-based ceramic membrane reactor to assess the reactor's suitability for thermochemical hydrogen production. The silica membranes were fabricated by depositing a thin silica layer onto the surface of porous alumina ceramic support tubes via counter-diffusion chemical vapor deposition of hexyltrimethoxysilane. The performance of the silica-based ceramic membrane reactor was evaluated by exploring important operating parameters such as the flow rates of the hydrogen iodide feed and the nitrogen sweep gas. The influence of the flow rates on the hydrogen iodide decomposition conversion was investigated in the lower range of the investigated feed flow rates and in the higher range of the sweep-gas flow rates. The experimental data agreed with the simulation results reasonably well, and both highlighted the possibility of achieving a conversion greater than 0.70 at decomposition temperature of 400 °C. Therefore, the developed silica-based ceramic membrane reactor could enhance the total thermal efficiency of the thermochemical process.

Solar-driven photoelectrochemical (PEC) hydrogen production offers a promising solution to simultaneously tackle the global energy crisis and the environmental pollution. Herein, we report a PEC cell of organic-inorganic hybrid perovskite (methylammonium lead iodide, MAPbI3)-TiO2 nanorod array (TNAs) for efficient and stable hydrogen evolution in aqueous hydrogen iodide (HI) solution. The built-in electric field created across the MAPbI3-TiO2 junction is able to efficiently separate the electron-hole pairs photogenerated in MAPbI3 with electrons quickly injected from MAPbI3 to TiO2, which are then transported along the one-dimensional TiO2 nanorod channels to the counter electrode to reduce proton to evolve hydrogen. The optimized MAPbI3-TNA PEC cell exhibits a high photocurrent density of 1.75 mA cm−2 at 0.14 V (vs. Ag/AgCl) under AM 1.5G illumination, which is able to stably produce molecular hydrogen at a rate of 33.3 μmol cm−2 h−1 for more than 8 h.

The potential of the silica membrane reactors for use in the decomposition of hydrogen iodide (HI) was investigated by simulation with the aim of producing CO2-free hydrogen via the thermochemical water-splitting iodine-sulfur process. Simulation model validation was done using the data derived from an experimental membrane reactor. The simulated results showed good agreement with the experimental findings. The important process parameters determining the performance of the membrane reactor used for HI decomposition, namely, reaction temperature, total pressures on both the feed side and the permeate side, and HI feed flow rate were investigated theoritically by means of a simulation. It was found that the conversion of HI decomposition can be improved by up to four times (80%) or greater than the equilibrium conversion (20%) at 400 °C by employing a membrane reactor equipped with a tubular silica membrane. The features to design the membrane reactor module for HI decomposition of the thermochemical iodine-sulfur process were discussed under a wide range of operation conditions by evaluating the relationship between HI conversion and number of membrane tubes.

The sulfur–iodine (SI) cycle is deemed to be one of the most promising alternative methods for large-scale hydrogen production by water splitting, free of CO2 emissions. Decomposition of hydrogen iodide is a pivotal reaction that produces hydrogen. The homogeneous conversion of hydrogen iodide is only 2.2% even at 773 K [1]. A suitable catalyst should be selected to reduce the decomposition temperature of HI and attain reaction yields approaching to the thermodynamic equilibrium conversion. However, residual H2SO4 could not be avoided in the SI cycle because of incomplete purification. The H2SO4 present in the HI feeding stream may lead to the poisoning of HI decomposition catalysts. In this study, the activity and sulfur poisoning of Ru and Ni catalysts loaded on carbon and alumina, respectively, were investigated at 773 K. HI conversion efficiency markedly decreased from 21% to 10% with H2SO4 (3000 ppm) present, which was reversible when H2SO4 was withdrawn in the case of Ru/C. In the case of Ru/C and Ni/Al2O3, catalyst deactivation depends on the concentration of H2SO4; the higher the concentration of H2SO4, the greater the severity of deactivation. Catalysts before and after sulfur poisoning were characterized by transmission electron microscopy (TEM), energy-dispersive X-Ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Experimental results and characterization of poisoned and fresh catalysts indicate that the catalyst deactivation could be ascribed to the competitive adsorption of sulfur species and change in its surface properties.

The current work presents the synthesis of carbon nanotubes supported palladium catalyst for hydrogen production from hydrogen-iodide decomposition in thermochemical water-splitting sulfur-iodine (SI) cycle. XRD results showed that the Pd nanoparticles were highly dispersed on the CNT support. Raman results showed that Pd(3%) possessed the highest quantity of defects than other loaded Pd samples and CNT support. The order of catalytic activity for hydrogen-iodide decomposition is: Pd(3%)/CNT > Pd(5%)/CNT > Pd(1%)/CNT > CNT. This is due to high degree of defects present in Pd(3%)/CNT as compared to others. Pd(3%)/CNT also showed an excellent stability of 100 h for the reaction. The post-characterizations (BET, ICP-AES, XRD and TEM) of spent-Pd(3%)/CNT after 100 h were carried out in order to find out the changes in the specific surface area, elemental analysis, structure and particle size. No changes were observed in the specific surface area, elemental analysis, particle size, and structure of the spent catalyst as compared to the fresh one. This shows the Pd/CNT has a lot of potential of generating hydrogen in the thermochemical SI cycle.

Sulfur-iodine thermochemical water splitting cycle is a promising and carbon dioxide-free method for hydrogen production. Among the reactions in this cycle, hydrogen iodide catalytic decomposition is the rate-determining step. In this study, catalytic reactivity test combined with characterizations of nitrogen physisorption, X-Ray diffraction, and Raman spectroscopy provide evidences that hydrofluoric acid modified semi-coke is a promising catalyst candidate for hydrogen iodide decomposition because of its high active and low cost. The raw semi-coke enhanced the hydrogen iodide conversion rate. After modification of hydrofluoric acid, the catalytic activity of semi-coke increased largely. Semi-coke modified by 40 wt% hydrofluoric acid showed better performance than commercial activated carbon catalyst. Combine the characterization results and catalytic reactivity, the graphitic edge carbon atoms in semi-coke are the active sites for hydrogen iodide decomposition. This finding pointed out the direction of carbon material catalyst design for hydrogen iodide decomposition.

We report the H I bond activation on free and confined silver tetramer clusters using the first principles approach. The objective of this study is to underscore the effect of confinement on the chemical reactivity of Ag4. All calculations were carried out under the density functional theory formalism using both atomic and plane wave basis sets. We have used armchair carbon nanotube as a model system for confinement. The results show that the interaction energy is increased inside nanotube, leading to enhanced bond stretching. The origin of such effect has been demonstrated using molecular orbital theory and electronic density of state analysis.

With the goal of eventually developing a replacement for the Claus process that also produces H 2 , we have explored the possibility of decomposing hydrogen sulfide through a thermochemical cycle involving iodine. The thermochemical cycle under investigation leverages differences in temperature and reaction conditions to accomplish the unfavorable hydrogen sulfide decomposition to H 2 and elemental sulfur over two reaction steps, creating and then decomposing hydroiodic acid. This proposed process is similar to ideas put forth in the 1980s and 1990s by Kalina, Chakma, and Oosawa, but makes use of thermochemical hydrogen iodide decomposition methods and catalysts rather than electrochemical or photoelectrochemical methods. Process models describing a potential implementation of this thermochemical cycle were created. Motivated by the process model results, experimentation showed the possibility of using alternative solvents to dramatically decrease the energy requirements for the process. Further process modeling incorporated these alternative solvents and suggests that this theoretical hydrogen sulfide processing unit has favorable economic and environmental properties.

HI decomposition in Iodine-Sulfur (IS) thermochemical process for hydrogen production is one of the critical steps, which suffers from low equilibrium conversion as well as highly corrosive environment. Corrosion-resistant metal membrane reactor is proposed to be a process intensification tool, which can enable efficient HI decomposition by enhancing the equilibrium conversion value. Here we report corrosion resistance studies on tantalum, niobium and palladium membranes, along with their comparative evaluation. Thin layer each of tantalum, palladium and niobium was coated on tubular alumina support of length 250 mm and 10 mm OD using DC sputter deposition technique. Small pieces of the coated tubes were subject to immersion coupon tests in HI-water environment (57 wt% HI in water) at a temperature of 125–130 °C under reflux environment, and simulated HI decomposition environment at 450 °C. The unexposed and exposed cut pieces were analyzed using scanning electron microscope (SEM), energy dispersive X-ray (EDX) and secondary ion mass spectrometer (SIMS). The extent of leaching of metal into liquid HI was quantified using inductively coupled plasma-mass spectrometer (ICP-MS). Findings confirmed that tantalum is the most resistant membrane material in HI environment (liquid and gas) followed by niobium and palladium.

One of the most important factors governing the photovoltaic efficiency and environmental stability of Perovskite Solar Cells (PSCs) is the quality of their perovskite films. However, the present study demonstrates that CH3NH3PbI3 perovskite films after anti-solvent washing are far from perfect on the surface, where the crystallization degree is quite low with complex multi-phases associated with numerous defects and notable chemical inhomogeneity. Herein, we report a novel anti-solvent washing treatment simply using Hydrogen Iodide (HI) additive in chlorobenzene (CB) which can enormously improve CH3NH3PbI3 films surface with high crystallization phase purity and chemical homogeneity, leading to excellent structural stability under humidity, heat and even tensile force. Based on such high quality films with defect-less surface, fabricated planar PSCs with an architecture of ITO/TiO2/CH3NH3PbI3/Spiro-OMeTAD/MoOx/Au present a champion PCE of 19.94% and improved stability under humidity. Moreover, fabricated flexible planar PSCs on PET/ITO substrates with a champion PCE of 17.32% are shown to be more robust under tensile force than their control devices. The present study thus not only provides more insight into the facile defects passivation process on the surface achieved via balancing halide ions, but also provides a practical but efficient treatment which can be widely used to fabricate high quality CH3NH3PbI3 films for environmentally stable high performance device applications.

In this work, TiO2 nanoparticles have been prepared by the sol–gel (at different calcination temperatures) and solution-combustion method for hydrogen-iodide decomposition in thermo-chemical water-splitting sulfur-iodine (SI) cycle for hydrogen production. The sol-gel method derived TiO2 (TiO2-SGM-300 and TiO2-SGM-500) provide smaller nanoparticles as compared to the solution-combustion (TiO2-SCM). TEM revealed a particle size of around 4–5 nm of TiO2-SGM-300. XRD and Raman confirmed that TiO2-SGM-300 and TiO2-SGM-500 exhibited pure anatase phase, whereas a small amount of rutile phase was observed in TiO2-SGM-700 and TiO2-SCM samples. It is found that with increase in calcination temperatures during sol-gel method, the average particle size of TiO2 increases and specific surface area decreases. Commercial TiO2 (Degussa P-25) was used for the comparison purpose. As far as the author knows, TiO2 has been used here for the first time for hydrogen-iodide decomposition. The hydrogen-iodide decomposition experiments were carried out in a vertical-fixed bed quartz reactor at a WHSV of 12.9 h−1 under atmospheric pressure. The order of catalytic activity was as follows: TiO2-SGM-300 > TiO2-SCM > TiO2-COMM (commercial). Also, it was observed that the hydrogen-iodide conversion decreases with increase in calcination temperatures of TiO2 during sol–gel method. Their activity was as follows: TiO2-SGM-300 > TiO2-SGM-500 > TiO2-SGM-700. TiO2-SGM-300 catalyst also showed a reasonable time-on-stream stability of 6 h for hydrogen-iodide decomposition. The apparent activation energy of TiO2-SGM-300 is found to be 72.29 kJ mol−1. This shows that the TiO2 has a potential of generating hydrogen from hydrogen iodide in SI cycle. This can further be explored as a catalyst support using some non-precious and precious metal catalysts for hydrogen-iodide decomposition.

The need to produce Hydrogen in an environmentally friendly manner has increased as the transportation industry has started to employ cleaner sources of energy. One of the cleaner ways to produce H2, is to use the Bunsen S-I cycle. This includes the separation of the H2 from an ionic mixture of Hydrogen Iodide and water using distillation. In this work, the Pitzer’s model for electrolyte solutions has been employed to represent the vapour-liquid equilibrium (VLE) of the binary system of HI and H2O. The activity coefficient (γ) is calculated from the equation which indicated the non-ideal nature of the system and aided the calculation of the vapour phase mole fraction. The experimental VLE data was obtained from a recirculating still at 101.3 kPa pressure for the binary system. This experimental data and data from literature was used to estimate the parameters of the Pitzer’s model to represent the activity coefficient of HI in this mixture. These optimized parameters could explain all the variations in the data with more that 90% accuracy for most of the data, with an average standard deviation of about 0.04. Furthermore, the temperature dependent form of the Pitzer’s equation was used to predict the VLE data at higher pressures of 3 and 5.7 bars and higher temperature conditions.

Graphene shows great promise as a high-efficiency electrothermal film for flexible transparent defoggers/defrosters. However, it remains a great challenge to achieve a good balance between the production cost and the properties of graphene films. Here, we proposed a cost-effective self-assembly method to fabricate high-performance, large-area graphene oxide/electrochemically exfoliated graphene hybrid films for heater applications. The self-assembled graphene hybrid films with the area of 20 × 20 cm2 could be transferred onto arbitrary substrates with nonplanar surfaces and simply patterned with the hard mask. After reduction by hydrogen iodide vapor followed by 800 °C thermal treatment, the hybrid films with the transmittance of 76.2% exhibit good heating characteristics and defogging performance, which reach a saturation temperature of up to 127.5 °C when 40 V was applied for 60 s.

The stability of perovskite is a bottleneck for the application of perovskite solar cells. Herein, 4-ethylamine Phenylphosphate disodium salt (EAPP) was explored as a functional surface ligand to passivate perovskite surface. As the addition of 1 mol% of EAPP, the degradation of the film in high humidity condition was effectively reduced. Solar cells based on EAPP doped perovskite film show merely slight decrease of its initial efficiency in high humidity condition, whereas the control device show catastrophic decrease. Apart from as a passivating molecule to protect perovskite from contacting with water, EAPP show function as a reducing reagent to bond with hydrogen iodide formed in perovskite decomposition.

A highly active and stable catalyst for hydrogen-iodide decomposition reaction in sulfur-iodine (SI) cycle has been prepared in the form of Pd CeO 2 nanocatalyst by sol-gel method with different calcination temperatures (300 °C, 500 °C, and 700 °C). XRD and TEM confirmed a size around 6–8 nm for Pd CeO 2 particles calcined at 300 °C. Raman study revealed large number oxygen vacancies in Pd CeO 2 -300 when compared to Pd CeO 2 -500 and Pd CeO 2 -700. With increase in calcination temperature, the average particle size increased whereas the specific surface area and number of oxygen vacancies decreased. Hydrogen-iodide catalytic-decomposition was carried out in the temperature range of 400°C–550 °C in a quartz-tube, vertical, fixed-bed reactor with 55 wt % aqueous hydrogen-iodide feed over Pd CeO 2 catalyst using nitrogen as a carrier gas. Pd CeO 2 -300 showed hydrogen-iodide conversion of 23.3%, which is close to the theoretical equilibrium conversion of 24%, at 550 °C. It also showed a reasonable stability with a time-on-stream of 5 h.

Developing cost-effective and high-performance catalysts in biomass chemistry is motivated by creating sustainable technologies dependent on inexpensive and abundant resources. The existing methods for the direct preparation of 5-methylfurfural (5-MF) from biomass-derived fructose mediated by hydrogen iodide (HI) mainly require precious metal catalysts. This research showed that low-cost tungsten carbide (WC) was capable to produce HI from iodine (I2) via liquid-phase hydrogenation, but a pivotal limitation was the poor stability under the combination effects of water and I2. To solve this problem, the bulk WC and the high dispersion supported WC were modified by hydrophobic organosilicones through simple liquid phase deposition. Both of the two superhydrophobic WC materials had better stability and their catalytic activity were comparable to the expensive palladium-carbon (Pd/C) catalyst in the preparation of 5-MF, especially the superhydrophobic high dispersion supported WC. This work highlights the potential of the low-cost WC with simple superhydrophobic modification in assisting the direct preparation of 5-MF from fructose mediated by HI, which has high significance to the sustainable development of the low-cost biomass chemical engineering.

Hydrogen iodide decomposition is the core hydrogen production step in the sulfur-iodine thermochemical cycle, which determines the hydrogen production rate and thermal efficiency of the device. The conventional decomposition reactor is limited by equilibrium conditions, so the hydrogen iodide conversion rate is low at normal reaction temperature, and membrane reactor technology can break the limit of equilibrium condition and greatly improve the conversion rate. Most of the previous hydrogen iodide membrane reactor models were built under isothermal conditions and did not consider the influence of different sweep modes. In this paper, a one-dimensional non-isothermal hydrogen iodide decomposition membrane reactor mathematical model in co-current and countercurrent sweep modes is established, and the effects of reactor parameter on hydrogen iodide conversion and hydrogen recovery rate are analyzed under the two sweep modes. The results show that the countercurrent mode can obtain higher hydrogen iodide conversion rate than the co-current mode under larger sweep flow rate, inlet pressure of reaction and permeation zone, reactor length; the maximum recovery rate of hydrogen in countercurrent mode is close to 100%. A modified membrane reactor structure combining the traditional reactor and membrane reactor is proposed, which could effectively increase the hydrogen permeation flux per unit membrane surface. In engineering application, the reasonable design of the modified membrane reactor can effectively reduce the investment cost of the membrane reactor on the premise of satisfying the hydrogen production rate.

Reactions of benzyl alcohols with HI in solvent-free conditions were examined. Three types of reactions (iodination, reduction, and ring formation) occurred depending on the degree of crowding around the benzyl position and the benzylic stabilization of substrates. Results also showed that the ring formation to give indanes proceeded efficiently when HI was used, and that compounds with electron-rich aromatic rings gave indane derivatives in good yields.

The decomposition of hydrogen iodide in the thermochemical water splitting iodine–sulfur process at an intermediate temperature (400 °C) using a catalytic membrane reactor was reported here, for the first time. The performance of a catalytic membrane reactor based on a hexyltrimethoxysilane-derived silica membranes (H2 permeance of 9.4 × 10−7 mol Pa−1 m−2 s−1 and H2/N2 selectivity of over 80.0.) was evaluated at 400 °C by varying the HI flow rates of 2.6, 4.7, 6.9, 8.4, and 9.7 mL min−1. The silica membranes were prepared by counter-diffusion chemical vapor deposition method on γ-alumina-coated α-alumina tubes. Hydrogen was successfully extracted from the membrane reactor using the silica membrane at 400 °C. A significant increase in HI conversion was achieved. The conversion achieved at an HI flow rate of 2.6 mL min−1 was approximately 0.60, which was greater than the equilibrium conversion in HI decomposition (0.22).

Exergy analysis method is applied to evaluate the performance of reactive distillation (RD) column in the acetic acid production process, at which acetic acid is produced via reaction between carbon monoxide and methanol with a soluble catalyst system consisting of rhodium complex (catalyst) and methyl iodide-hydrogen iodide (promoter). In this column, desired purity of the product is obtained through reaction between methanol and hydrogen iodide. The effects of different operational parameters on the separation and the exergy efficiencies of this RD column are evaluated by sensitivity analysis, finally, the response surface methodology (RSM) method is applied for modeling and optimization of the exergy loss. The adequacy of the developed model for exergy losses in the reactive distillation column is evaluated using analysis of variances (ANOVA). The result of ANOVA study shows that the most effective operating parameters are feed stream temperature, boilup ratio, and reflux ratio. As the result of this optimization the exergy losses and energy consumption for the reactive distillation column reduced by 28% and 12% respectively. This study shows that RSM method besides the exergy concept could be an appropriate tool for optimization of complex and energy intensive reactive distillation systems.

Based on our previous study on the experimental performance tests of the catalyst-packed type HI thermal decomposer and bayonet type H 2 SO 4 thermal decomposer for a 50 NL-H 2 /h SI test facility, which were directly heated using electrical heating chambers, semi-pilot scale H 2 SO 4 and HI decomposers for the 1 N m 3 -H 2 /h SI test facility coupled to an out-of-pile helium loop have been designed, and it was theoretically confirmed that the design specifications satisfy the hydrogen production capacity based on a Computational Fluid Dynamics (CFD) analysis. The effects of the overall heat transfer coefficient on the helium outlet temperatures and decomposition percentages of the decomposers were identified. The H 2 SO 4 and HI decomposers proposed are capable of outlet helium temperatures of 734 °C and 383 °C for an overall heat transfer coefficient of 5 W/m 2 K, respectively, which satisfy the operating temperature conditions of the out-of-pile helium loop. The average thermal decomposition percentages of the proposed decomposers are 60.4% for sulfuric acid and 22.4% for hydrogen iodide. These decomposition percentages obtained from the numerical results are acceptable with a hydrogen production rate of 1 N m 3 -H 2 /h. Modification points of the decomposers to increase the decomposition percentages are suggested, such as a minimization of heat loss into the atmosphere and optimization of component designs.

A high-performance, H2-permselective silica membrane derived from hexyltrimethoxysilane (HTMOS) was developed for application in the thermochemical water-splitting iodine–sulfur process. Silica membranes, referred to here as HTMOS membranes, were prepared via counter-diffusion chemical vapor deposition on γ-alumina-coated α-alumina support tubes with outer diameters of 10 mm. Special attention was devoted to obtain high H2/HI selectivity, high H2 permeance, and good stability in the presence of corrosive HI gas. The effects of the deposition conditions, temperature, and period were investigated. The HTMOS membrane prepared at 450 °C for 5 min exhibited high H2/HI selectivity (>175) with H2 permeance on the order of 10−7 mol Pa−1 m−2 s−1. On the basis of stability experiments, it was found that the HTMOS membrane was stable upon HI exposure at a temperature of 400 °C for 11 h.

Hydrogen production from nuclear energy has attracted considerable interest as a clean energy solution to address the challenges of climate change and environmental sustainability. With respect to the large-scale and economical production of hydrogen using nuclear energy, the thermochemical water-splitting iodine-sulfur (IS) process is a promising method. The IS process uses sulfur and iodine compounds to decompose water into its elemental constituents, hydrogen and oxygen, by using three coupled chemical reactions: the Bunsen reaction; sulfuric acid decomposition; and hydrogen iodide (HI) decomposition. The decomposition of HI is the efficiency-determining step of the process. In this work, a membrane reactor with a silica membrane closed on one end was designed, and its potential for hydrogen production from HI decomposition was explored. In the reactor-module design, only one end of the membrane tube was fixed, while the closed-end of the tube was freely suspended to avoid thermal expansion effects. The closed-end silica membranes were prepared for the first time by a counter-diffusion chemical vapor deposition of hexyltrimethoxysilane. In application, HI conversion of greater than 0.60 was achieved at a decomposition temperature of 400 °C, which is three times greater than the equilibrium conversion (0.20). Thus, the membrane reactor with closed-end silica membrane was shown to produce a successful equilibrium shift in the production of hydrogen via HI decomposition in the thermochemical IS process.

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.

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.

To develop the utilization of HI as an ‘old but new’ reagent, we found that the reaction of acetophenone analogues with HI gas proceeded to give an α-alkylated product, which is derived from the two ketone molecules. It was possible to conduct the reaction in solvent-free and various organic solvents under anhydrous conditions. From the investigation on the reaction mechanism, we proposed that HI acts as an acid and a reducing agent.

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.

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.

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.

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 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.

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.

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.

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 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.

A flowsheet of the thermochemical H2S splitting cycle was designed and simulated for hydrogen and sulfur production. The heat and mass balance, as well as the thermal efficiency of the process, were calculated. A thermal efficiency of 40.865% for hydrogen production was obtained by optimizing the heat exchangers and the EED cell considering waste heat recovery. The effects of five calculation parameters, namely, the sulfuric acid concentration, hydrogen iodide (HI) conversion ratio, molar flow rate of HIx phase, pressure, and reflux ratio at the distillation column, on thermal efficiency were evaluated. The results indicated that further research on the membrane reactor is needed. The optimized conditions for the over-azeotropic HI solution yield should be prioritized. Furthermore, an H2SO4 concentration system should be reasonably designed to reduce the complexity of the process and equipment settings, as well as to improve thermal efficiency.

The preliminary flowsheet of an electrodialysis cell (EDC) and membrane reactor (MR)-embedded SI cycle has been developed. The key components consisting of the preliminary flowsheet are as follows: a Bunsen reactor having a mutual separation function of sulfuric acid and hydriodic acid phases, a sulfuric acid refined column for the purification of the sulfuric acid solution, a HIx-refined column for the purification of the hydriodic acid solution, an isothermal drum coupled to a multi-stage distillation column to concentrate the sulfuric acid solution, a sulfuric acid vaporizer, a sulfuric acid decomposer, a sulfur trioxide decomposer, a sulfuric acid recombination reactor, a condensed sulfuric acid solution and sulfur dioxide/oxygen gas mixture separator, a precipitator to recover excess iodine dissolved in the hydriodic acid solution, an electrodialysis cell to break through the azeotrope of the HI/I2/H2O ternary solution, a multi-stage distillation column to generate highly concentrated hydriodic acid vapor as a top product of the column, a membrane reactor to decompose hydrogen iodide and preferentially separate the hydrogen, and a hydrogen scrubber. The material and energy balance of each component was established based on a computer code simulation using Aspen Plus™. The thermal efficiency of the EDC and MR-embedded SI process has also been evaluated and predicted as 39.4%.