HI Solution Research Articles

Reduction of styrene compounds by hydrogen iodide

Reduction of styrene compounds was achieved by the simple method of adding more than 2.5 equivalents of an aqueous HI solution in chlorobenzene under refluxing conditions for 8 h to give the product in medium to excellent yields. There was no need to add further additional reagent and catalyst. HI was a specific reagent for this reduction reaction. Increment of the amount of HI was efficient to increase the yield rather than to elongate the reaction time. This reaction could be applied to compounds bearing halogen and sulfur atoms, which would act as reductive site and poisoning of the transition-metal catalyst, respectively. The yield was decreased in the case of the compounds bearing small substituent such as propyl and butyl groups on olefin. This reaction proceeded via the iodinated intermediate followed by the reduction of C-I bond. The reduction mechanism would contain the radical cleavage of the C-I bond.

Solvent assisted shape dependent MAPbI3/polyfluorene heterostructures with a larger surface area for improved photocatalytic H2 evolution

Although lead based MAPbI3 has been used as a material for photocatalytic hydrogen evolution, conventionally synthesized MAPbI3 in HI solution suffers from very low HER activity with a hydrogen evolution rate of 30 μmol h−1 g−1.

Stable and efficient Ti3C2 MXene/MAPbI3-HI system for visible-light-driven photocatalytic HI splitting

Photo absorbing perovskites i.e. MAPbI3 have recently been emerging as promising photocatalysts for H2 evolution from HI solution. However, the adverse charge recombination of MAPbI3 at the nanoscale domain hinders its photocatalytic H2 evolution reaction (HER) performance. To address this issue, the metallic Ti3C2 MXene nanosheets is in-situ anchored on MAPbI3 to construct stable and efficient MXene/MAPbI3-HI system for visible-light-driven photocatalytic H2 evolution. The exfoliated MXene is approximate two-layer with the thickness of ∼2.52 nm, and a series of optical/optoelectrochemical characterizations demonstrate that the two layered MXene is capable of rapidly transporting the electrons from MAPbI3 to effectively inhibit the charge recombination and simultaneously providing abundant active sites for H+ reduction and H2 evolution. As a result, the photocatalytic performance of the MXene/MAPbI3 in term of HER rate and stability is greatly promoted, with an extremely high HER rate of 3124 μmol h−1 g−1. This work provides a rational route on the reliable design and synthesis of high-efficiency and stable 2D electron transport/3D light absorber perovskite-based photocatalysts.

Process optimization and safety assessment on a pilot-scale Bunsen process in sulfur–iodine cycle

This study investigates Bunsen reaction in the sulfur-iodine (SI) cycle for optimal conditions and specification of equipment in terms of the maximum HI yield and the least impurities in HIx (mixture of HI, I2 and H2O), the reaction safety, and dispersion of SO2 gas and HIX solution for leakage accident. The pilot-scale Bunsen process was simulated and validated. The optimization of the Bunsen reactor, 3-phase separator, and HIX purifier have been investigated in order to parameterize the operating conditions and equipment specification for three cases: (1) Maximize the HI yield for the final product (2) Minimize the H2SO4 impurities (3) Multi-objective case of both maximum HI production and minimum impurities. The gas reactivity safety was investigated on HI, H2SO4, I2, SO2, H2O, and O2. Also, the SO2 gas dispersion distance for 30 ppm, 0.75 ppm, and 0.2 ppm and HI dispersion distance for 120 ppm, 25 ppm, and 1 ppm was investigated for targeted unit operators at each optimization scenario. The deviation between pilot-scale experiment and simulation case falls within 1–3% for Bunsen reactor, 6~8% for 3-phase separator, and 2~4% for HIX purifier. The maximized HI production was increased by 17% for the maximum HI yield case from the designed case. The size and temperature of the Bunsen reactor was increased to enhance the reaction. However, the HIX purifier size was reduced since reverse Bunsen reaction causes loss in HI product. The H2SO4 impurities in the minimize H2SO4 impurities case were reduced by 71% from the designed case. The size of the Bunsen reactor remained the same as design case, but the HIX purifier size was increased to enhance the reverse Bunsen reaction. For multi-objective case, the HI productivity was increased by 16% and the H2SO4 impurities were reduced by 67% simultaneously. According Chemical Reactivity Worksheet (CRW) result, O2 should therefore not be stored with any components except iodine. For SO2 and HIX dispersion assessment, the maximum HI yield case reveals the maximum dispersion of SO2 gas and HIX solution from the Bunsen reactor. The dispersion from 3-phase separator was almost the same for all the cases. For HIX purifier, the minimum H2SO4 case exhibited the longest distance of SO2 gas and HI solution dispersion. At 3 bar and 140 °C, the maximum SO2 and HIX dispersion distance were occurred.

Electrochemical fabrication of polyaniline/graphene paper (PANI/GP) supercapacitor electrode materials on free-standing flexible graphene paper

Free-standing flexible supercapacitive electrodes have practical application for wearable energy storage devices. In this paper, graphene paper (GP), a flexible electrode substrate, was prepared by one-step reduction of graphene oxide (GO) using HI solution. GP can be used independently as a flexible electrode with specific capacitance of 227 F/g. In order to make up for the shortage of GP specific capacitance storage, polyaniline (PANI) with high specific capacitance and good electrical conductivity was selected to composite with GP by electrochemical polymerization approach. This method to fabricate electrode material by direct electrochemical polymerization avoids the use of conductive binder and organic solvent. Owing to the specific capacitance contribution of PANI and GP, the PANI/GP composites exhibit higher specific capacitance when the polymerization time is 30 s and the polymerization voltage is 0.8 V. At 1 A/g current density, the specific capacitance of composite is up to 759 F/g, which is 3.34 times of neat GP.

Chemoselective Reduction of α,β-Unsaturated Carbonyl and Carboxylic Compounds by Hydrogen Iodide

Abstract The selective reduction of α,β-unsaturated carbonyl compounds was achieved to produce saturated carbonyl compounds with aqueous HI solution. The introduction of an aryl group at an α or β position efficiently facilitated the reduction with good yield. The reaction was applicable to compounds bearing carboxylic acids and halogen atoms. Through the investigation of the reaction mechanism, it was found that Michael-type addition of iodide occurred to produce β-iodo compounds followed by the reduction of C-I bond via anionic and radical paths.

Ti3C2Tx/RGO//PANI/RGO all-solid-state asymmetrical fiber supercapacitor with high energy density and superior flexibility

Ti3C2Tx nanosheets/reduced graphene oxide (Ti3C2Tx/RGO-0.9) fiber with superior flexibility and high volumetric capacitance is prepared by spinning the suspension of Ti3C2Tx nanosheets and graphene oxide (GO) nanosheets and followed by treating in HI solution at 80 °C. The oxidation of Ti3C2Tx nanosheets can be effectively protected in N2 atmosphere at 5 °C, and the as-prepared Ti3C2Tx/RGO-0.9 fiber electrode shows a specific volume capacitance of 415 F cm−3 at a current density of 1 A cm−3 in 1 M H2SO4 electrolyte and superior flexibility. Ti3C2Tx/RGO//PANI (polyaniline)/RGO all-solid-state asymmetrical fiber supercapacitor (AFSC) is assembled by using Ti3C2Tx/RGO-0.9 fiber as negative electrode and PANI/RGO-0.4 fiber as positive electrode in PVA-H2SO4 gel electrolyte, it exhibits not only excellent volumetric capacitance of 25 F cm−3 at a current density of 20 mA cm−3, but also high energy density of up to 3.4 mWh cm−3 at a power density of 10.2 mW cm−3. Moreover, the assembled AFSC shows outstanding flexibility and mechanical property, its volumetric capacitance has no obvious change after bending 500 times. The high energy density and superior mechanical flexibility make it can be used as a promising flexible power source in the fields of portable wearable electronic devices.

Lead-Free Halide Perovskite Cs3 Bi2 x Sb2-2 x I9 (x ≈ 0.3) Possessing the Photocatalytic Activity for Hydrogen Evolution Comparable to that of (CH3 NH3 )PbI3.

Lead-free perovskites Cs3 Bi2 x Sb2-2 x I9 (x = 0.1, 0.3, 0.5, 0.7, 0.9) are prepared by a co-precipitation method and their photocatalytic performance for hydrogen production is studied in aqueous HI solution. Compared with the lead-based perovskite (CH3 NH3 )PbI3 , Cs3 Bi2 x Sb2-2 x I9 has a better catalytic performance under air mass 1.5 G (AM 1.5 G) simulated sunlight (100 mW cm-2 ), powders of Cs3 Bi0.6 Sb1.4 I9 (100 mg) loaded with Pt nanoparticles show < H2 evolution rate of 92.6 µmol h-1 , which greatly exceeds that of (CH3 NH3 )PbI3 powders loaded with Pt nanoparticles (100 mg catalyst, 4 µmol h-1 ). The Cs3 Bi2 x Sb2-2 x I9 has a high stability, with no apparent decrease in catalytic activity after five consecutive H2 evolution experiments. The doping of Sb in Cs3 Bi2 x Sb2-2 x I9 effectively reduces the contribution of Bi3+ on the conduction band, attenuating the effect of Bi vacancy on band structure. Compared with pure Cs3 Bi2 I9 and Cs3 Sb2 I9 , Cs3 Bi2 x Sb2-2 x I9 has fewer midgap states and better optical absorption, which greatly enhances its performance for the hydrogen evolution reaction.

Lead-Free, Water-Stable A3 Bi2 I9 Perovskites: Crystal Growth and Blue-Emitting Quantum Dots [A=CH3 NH3 + , Cs+ , and (Rb0.05 Cs2.95 )+

Despite the great success in the increase in the power conversion efficiency of lead halide perovskite solar cells, the toxicity of lead and the unstable nature of the materials are still major concerns for their wider implementation at the industrial level. Herein, large-size single crystals (SCs) are developed in HI solution by using a temperature lowering method and nanocrystals (NCs) of A3 Bi2 I9 perovskites [where A=CH3 NH3 + (MA)+ , Cs+ , and (Rb0.05 Cs2.95 )+ ] are formed in ethanol (EtOH) and toluene (TOL). The stability of A3 Bi2 I9 perovskite is investigated by immersing the SCs for 24 h and pellets for 12 h in water. Moreover, the A3 Bi2 I9 perovskite NCs displays a promising photoluminescence quantum yield of 17.63 % and a long lifetime of 8.20 ns.

New Acidic Precursor and Acetone-Based Solvent for Fast Perovskite Processing via Proton-Exchange Reaction with Methylamine.

A new solvent system for PbI2 based on HI solution in acetone with a low boiling point is proposed. High solubility of PbI2 is caused by the formation of iodoplumbate complexes, and reaches a concentration of 1.6 M. Upon its crystallization metastable solvate phases PbI2∙HI∙n{(CH3)2CO} are formed. The latter allows for their easy deposition on substrates in a form of smooth and uniform thin films by spin-coating. Through a fast acid-base reaction with a gaseous amine, the films of the intermediate phase can be completely converted to single-phase perovskite films. The developed method allows one to form smooth perovskite films with high crystallinity with a thickness up to 1 μm. Due to easy and fast processing, the developed method can be promising for perovskite technology upscaling.

Materials resistance to corrosion by I2–HI–H2O mixtures for the realization of a sulfur-iodine plant

The substances involved in the sulfur-iodine (SI) thermochemical cycle to produce H2 by water splitting are very corrosive and may attack reactors, pumps, catalysts supports, and whatever part of the plant. This paper investigates the corrosion exerted by HI solutions in liquid, boiling, and gaseous phase at different temperatures. It shows the broadest overview of the behavior of different materials, ranging from pure metals to metallic alloys, from carbon materials to organic polymers, from ceramic materials to composite ones. Commercial nickel alloys and the effect of a specific element in their composition have here considerable attention. Regarding the composites materials, the impact of the substrate as well as the coating nature and thickness is studied, also through SEM-EDS (Scan Electron Microscope Energy Dispersive Spectroscopy) investigations.Carbon materials performed well, while most of the analyzed materials showed intergranular corrosion, pitting phenomena, and sometimes, carbide precipitation in the higher energy zones.

Few-layer black phosphorus-on-MAPbI3 for superb visible-light photocatalytic hydrogen evolution from HI splitting

Organic-inorganic perovskites like MAPbI3 with excellent optoelectric properties have recently gained concerns in photocatalytic HI splitting. However, their achieved hydrogen evolution reaction (HER) rates are still insufficient. Herein, a 2D few-layer black phosphorus (BP) as cocatalyst was anchored on MAPbI3 via electrostatic coupling. The resultant BP/MAPbI3 is rather stable in HI solution during the whole photoreaction, yielding a superb HER rate of 3742 μmol h−1 g−1 under visible irradiation, which is two orders of magnitude higher than that of MAPbI3-only, far higher than that of MAPbI3/Pt and also shows the advanced HER performance among MAPbI3 based systems. The remarkably boosted HER activity is thoroughly explored by optical/optoelectrochemical measurements, showing that BP can act as an electron promoter to trap electrons derived from MAPbI3 through a type I heterojunction in the interface. This contributes to a new paradigm for high-efficiency photocatalysts by anchoring non-metal cocatalyst onto MAPbI3 for solar energy conversion.

Ni3C-Decorated MAPbI3 as Visible-Light Photocatalyst for H2 Evolution from HI Splitting

A stable composite photocatalyst, that is, MAPbI3 decorated with Ni3C, is synthesized by a facile surface charge-promoted self-assembly approach and is demonstrated to be a high-efficiency, stable visible-light photocatalyst for H2 evolution in aqueous MAPbI3-saturated HI solution with H3PO2 as a stabilizer. The optimal 15% Ni3C/MAPbI3 suspension under visible illumination displays the hydrogen evolution reaction (HER) rate of 2362 μmol g–1 h–1, which is approximately 55-fold higher than that of MAPbI3 (43 μmol g–1 h–1) and far superior to that of Pt/MAPbI3 (534 μmol g–1 h–1). In particular, the Ni3C/MAPbI3 photocatalyst is ultrastable, showing no obvious decrease of HER activity in a given HER process, that is, 10 runs, one-month storage, and another 10 runs. The origin of the superior performance is proven to be predominantly attributed to the improved capabilities of charge carrier transfer and separation as well as the massive reactive centers on the surface of MAPbI3 by Ni3C decoration, together with...

A redox flow battery with high capacity retention using 12-phosphotungstic acid/iodine mixed solution as electrolytes

An electrolyte solution that includes redox couples is an essential component of a redox flow battery (RFB), and it directly affects the efficiency, power density, and cycle stability of the device. In this work, 12-phosphotungstic acid (PTA), a keggin type heteropolyacid, is evaluated as a redox active material in negative electrolyte. PTA has high redox reversibility and electrochemical activity with a kinetic constant of 0.015 cm s−1 and a low permeability of 6.17 × 10−10 cm2 min−1 through a Nafion®211 membrane. A single RFB is assembled with PTA and HI as the negative and positive redox active materials, respectively. The cell has a specific capacity of 12.8 Ah·L−1 at 100 mA cm−2; however, it exhibits poor cycle stability because of the osmotic pressure imbalance between the electrolyte solutions, the permeation of I−, and the serious hydrogen evolution side reaction. Using a mixed solution of PTA and HI as electrolytes on both sides of the cell and by adjusting the charge cutoff voltage, the cycle stability improved significantly. During 700 charge/discharge cycles at 100 mA cm−2, the battery has high coulombic efficiency of 99.6%, energy efficiency around 80.1%, and capacity retention of 99.99% per hour.

On the 1D viscous reactive and radiative gas with the first‐order Arrhenius kinetics

In this paper, we shall establish the global existence and exponential stability of solutions in Hi(i = 1,2,4) for a Stefan‐Boltzmann model of a viscous, reactive, and radiative gas with the first‐order Arrhenius kinetics in a bounded interval.

R&amp;D status of hydrogen production test using IS process test facility made of industrial structural material in JAEA

Abstract Thermochemical water splitting by means of the iodine-sulfur (IS) process is one of the promising candidates of CO2-free hydrogen production. Japan Atomic Energy Agency (JAEA) has been conducting R&D on the IS process since the end of the 1980s. A test facility has been constructed using corrosion-resistant industrial structural materials to verify the integrity of chemical plant components and demonstrate continuous and stable hydrogen production. A trial operation was successfully carried out for 8 h with a hydrogen production rate of approximately 10 NL/h. To improve the facility for enhancing the operation stability, a shaft seal technology was developed for a corrosion-resistant pump, which is the key device for feeding HI solution with high concentrations of iodine. The shaft seal technology features purge gas supply and solvent supply to the shaft seal part of the pump to prevent I2 precipitation, which causes pump malfunction. Upon introduction of the developed shaft seal technology, the duration of the hydrogen production operation was extended to 31 h (hydrogen production rate of approximately 20 NL/h).

Role of I2 Molecules and Weak Interactions in Supramolecular Assembling of Pseudo-Three-Dimensional Hybrid Bismuth Polyiodides: Synthesis, Structure, and Optical Properties of Phenylenediammonium Polyiodobismuthate(III)

Phenylenediammonium polyiodobismuthate(III), [PDA(BiI4)2·I2] (PDA = phenylenediammonium, [NH3C6H4NH3]2+), represents a new hybrid halometallate synthesized in a form of black well-shaped crystals by a facile reaction in aqueous solution of HI containing dissolved I2. It crystallizes in triclinic space group P1 with the unit cell parameters a = 7.761(1) A, b = 9.259(1) A, c = 9.689(1) A, α = 95.68(3)°, β = 103.19(3)°, γ = 93.56(3)°, and Z = 1. Its crystal structure comprises three levels of organization discriminated by a type of chemical bonding. The first level is provided by covalently bonded [BiI6] octahedra linked into [BiI4]∞– one-dimensional anionic chains; the second level features secondary bonds between the chains and I2 bridging molecules, whereas the third level is specified by the weak hydrogen N–H···I bonds involving a diammonium cation and I···I intermolecular interactions that additionally link anionic chains. Altogether, these three interaction types ensure the formation of a complex pseu...

Optical properties of CH3NH3PbI3 single crystal

CH3NH3PbI3 single crystals were successfully grown from HI solution by cooling method, and their structure were studied by X-ray diffraction. The Eg value of CH3NH3PbI3 single crystal determined by transmission spectrum was 1.51 eV. Low-temperature photoluminescence spectra of CH3NH3PbI3 single crystal show that a phase transition occurs at 160 K, the luminescence mechanism might be the intrinsic transition. And with the temperature rising, the “Varshni” trend is observed in CH3NH3PbI3 single crystal, indicating the change of Eg with temperature. Additionally, the Eg value obtained from the first principles is agree well with experimental result, and the DOS shows that Pb and I atoms have main contribution on the electric properties. Our results show that the CH3NH3PbI3 single crystals grown are of low trap density and have broad application prospects in the field of photoelectric devices. And low-temperature PL studies give supports on the direct-indirect character of CH3NH3PbI3 single crystal.

Composite of CH3 NH3 PbI3 with Reduced Graphene Oxide as a Highly Efficient and Stable Visible-Light Photocatalyst for Hydrogen Evolution in Aqueous HI Solution.

A facile and efficient photoreduction method is employed to synthesize the composite of methylammonium lead iodide perovskite (MAPbI3 ) with reduced graphene oxide (rGO). This MAPbI3 /rGO composite is shown to be an outstanding visible-light photocatalyst for H2 evolution in aqueous HI solution saturated with MAPbI3 . Powder samples of MAPbI3 /rGO (100 mg) show a H2 evolution rate of 93.9 µmol h-1 , which is 67 times faster than that of pristine MAPbI3 , under 120 mW cm-2 visible-light (λ ≥ 420 nm) illumination, and the composite is highly stable showing no significant decrease in the catalytic activity after 200 h (i.e., 20 cycles) of repeated H2 evolution experiments. The electrochemiluminescence performance of MAPbI3 is investigated to explore the charge transfer process, to find that the photogenerated electrons in MAPbI3 are transferred to the rGO sites, where protons are reduced to H2 .

High performance hole transport material free perovskite solar cells from a low pure PbI2 source using a facile solid-gas reaction process

Abstract Preparing CH3NH3PbI3 perovskite solar cells from a low pure lead source is highly desirable for cutting down the fabrication cost of perovskite solar cells. To avoid the low solubility problem of low pure PbI2 source in the commonly used solvent, PbI2 first reacts with HI solution to produce highly soluble HPbI3 compound, then CH3NH3PbI3 perovskite film is obtained through a solid-gas reaction between HPbI3 film and CH3NH2 vapor. By optimizing the concentration of HPbI3 precursor solution, highly uniform perovskite films are obtained. Hole transport material free perovskite solar cells fabricated via this facile method exhibit an average power conversion efficiency of 12.90% and a maximum power conversion efficiency of 13.21%, which are comparable to the performances of perovskite solar cells prepared from high pure PbI2 sources.