1333-74-0 Usage
Chemical Description
Hydrogen is a chemical element with the symbol H.
Chemical Description
Hydrogen is a colorless, odorless, and tasteless gas that is the lightest element in the periodic table.
Chemical Description
Hydrogen and Raney nickel are used for the reduction of nitro compounds to the corresponding amines.
Chemical Description
Hydrogen and oxygen are gases used to generate radicals in the gas phase, while urea and maleic acid are compounds in the water phase that react with the radicals.
Uses
Used in Chemical Production:
Hydrogen is used as a reducing agent and in the production of ammonia (NH3), ethanol (ethyl alcohol made from grains), and hydrogenation of vegetable oils.
Used in Industrial Processes:
Hydrogen is used in refineries, petrochemical and bulk chemical facilities for hydrotreating, catalytic reforming, and hydrocracking. It is also used in the chemical, metallurgical, fats and oils, glass, and electronic industries. Some of these industries receive hydrogen in gaseous form in cylinders or tube trailers, or as liquid hydrogen delivered into on-site storage systems.
Used in Welding and Cutting:
Hydrogen is used in oxy-hydrogen blowpipes for welding and limelight, as well as in autogenous welding of steel and other metals.
Used in Balloons and Airships:
Hydrogen is used as a lifting gas in balloons and airships due to its lightness.
Used in Metallurgy:
Hydrogen is used in metallurgy to reduce oxides to metals.
Used in Petroleum Refining:
Hydrogen is used in petroleum refining processes.
Used in Thermonuclear Reactions:
Hydrogen ionizes to form protons, deuterons (D), or tritons (T) in thermonuclear reactions.
Used in Scientific Research:
Liquid hydrogen is used in bubble chambers to study subatomic particles and as a coolant.
Used in Agricultural Processes:
Hydrogen is used in the Haber-Bosch process for producing ammonia, a major raw material for nitrogenous fertilizers. It is also used in the catalytic hydrogenation of unsaturated vegetable oils to make solid fats and in petroleum refining.
Physical Properties:
Hydrogen has a density of 0.08988 g/l, with a melting point of -255.34°C and a boiling point of -252.87°C. It is noncorrosive and can be contained at ambient temperatures by most common metals used in installations designed for sufficient working pressures. However, equipment and piping should be selected with consideration of the possibility of embrittlement, particularly at elevated pressures and temperatures above 450°F (232°C). Metals used for liquid hydrogen equipment must have satisfactory properties at very low operating temperatures, with suitable materials including austenitic chromium-nickel steels (stainless steels), copper, copper silicon alloys, aluminum, Monel, and some brasses and bronzes.
Isotopes
The major isotope of hydrogen has just one proton and no neutrons in itsnucleus (1H-1).Deuterium (2D or H-2) has a nucleus consisting of one proton plus one neutron. Tritium (3T or H-3), another variety of heavy water (TOT),has nuclei consisting of one proton and two neutrons.
Origin of Name
Hydrogen was named after the Greek term hydro genes, which means
“water former.”
History
Hydrogen was prepared many years before it was recognized as a distinct substance by Cavendish in 1766. It was named by Lavoisier. Hydrogen is the most abundant of all elements in the universe, and it is thought that the heavier elements were, and still are, being built from hydrogen and helium. It has been estimated that hydrogen makes up more than 90% of all the atoms or three quarters of the mass of the universe. It is found in the sun and most stars, and plays an important part in the proton– proton reaction and carbon–nitrogen cycle, which accounts for the energy of the sun and stars. It is thought that hydrogen is a major component of the planet Jupiter and that at some depth in the planet’s interior the pressure is so great that solid molecular hydrogen is converted into solid metallic hydrogen. In 1973, it was reported that a group of Russian experimenters may have produced metallic hydrogen at a pressure of 2.8 Mbar. At the transition the density changed from 1.08 to 1.3 g/cm3. Earlier, in 1972, a Livermore (California) group also reported on a similar experiment in which they observed a pressure-volume point centered at 2 Mbar. It has been predicted that metallic hydrogen may be metastable; others have predicted it would be a superconductor at room temperature. On Earth, hydrogen occurs chiefly in combination with oxygen in water, but it is also present in organic matter such as living plants, petroleum, coal, etc. It is present as the free element in the atmosphere, but only to the extent of less than 1 ppm by volume. It is the lightest of all gases, and combines with other elements, sometimes explosively, to form compounds. Great quantities of hydrogen are required commercially for the fixation of nitrogen from the air in the Haber ammonia process and for the hydrogenation of fats and oils. It is also used in large quantities in methanol production, in hydrodealkylation, hydrocracking, and hydrodesulfurization. It is also used as a rocket fuel, for welding, for production of hydrochloric acid, for the reduction of metallic ores, and for filling balloons. The lifting power of 1 ft3 of hydrogen gas is about 0.076 lb at 0°C, 760 mm pressure. Production of hydrogen in the U.S. alone now amounts to about 3 billion cubic feet per year. It is prepared by the action of steam on heated carbon, by decomposition of certain hydrocarbons with heat, by the electrolysis of water, or by the displacement from acids by certain metals. It is also produced by the action of sodium or potassium hydroxide on aluminum. Liquid hydrogen is important in cryogenics and in the study of superconductivity, as its melting point is only a 20°C above absolute zero. Hydrogen consists of three isotopes, most of which is 1H. The ordinary isotope of hydrogen, H, is known as protium. In 1932, Urey announced the discovery of a stable isotope, deuterium (2H or D) with an atomic weight of 2. Deuterium is present in natural hydrogen to the extent of 0.015%. Two years later an unstable isotope, tritium (3H), with an atomic weight of 3 was discovered. Tritium has a half-lifeof about 12.32 years. Tritium atoms are also present in natural hydrogen but in a much smaller proportion. Tritium is readily produced in nuclear reactors and is used in the production of the hydrogen bomb. It is also used as a radioactive agent in making luminous paints, and as a tracer. On August 27, 2001 Russian, French, and Japanese physicists working at the Joint Institute for Nuclear Research near Moscow reported they had made “super-heavy hydrogen,” which had a nucleus with one proton and four neutrons. Using an accelerator, they used a beam of helium-6 nuclei to strike a hydrogen target, which resulted in the occasional production of a hydrogen-5 nucleus plus a helium-2 nucleus. These unstable particles quickly disintegrated. This resulted in two protons from the He-2, a triton, and two neutrons from the H-5 breakup. Deuterium gas is readily available, without permit, at about $1/l.
Characteristics
H2 is a diatomic gas molecule composed of two tightly joined atoms that strongly sharetheir outer electrons. It is an odorless, tasteless, and colorless gas lighter than air. Hydrogenis included in group 1 with the alkali metals because it has an oxidation state of +1 as dothe other alkali metals. Experiments during the 1990s at the Lawrence Livermore NationalLaboratory (LLNL), in Livermore, California, lowered the temperature of H2 to almostabsolute zero. By exploding gunpowder in a long tube that contained gaseous hydrogen, thegas that was under pressure of over one million times the normal atmospheric pressure wascompressed into a liquid. This extreme pressure on the very cold gas converted it to liquidhydrogen (almost to the point of solid metallic hydrogen), in which state it did act as a metaland conduct electricity.Hydrogen gas is slightly soluble in water, alcohol, and ether. Although it is noncorrosive,it can permeate solids better than air. Hydrogen has excellent adsorption capabilities in theway it attaches and holds to the surface of some substances. (Adsorption is not the same asabsorption with a “b,” in which one substance intersperses another.
Production Methods
Hydrogen gas may be produced by several methods. It is commerciallyobtained by electrolysis of water. It also is made industrially by the reactionof steam with methane or coke:
CH4 + H2O → CO + 3H2
C + H2O → CO + H2
CO + H2O → CO2 + H2
The reactions are carried out at about 900 to 1,000°C and catalyzed by nick-el, nickel-alumina, or rhodium-alimina catalysts. In the laboratory, hydrogenmay be prepared by the reaction of zinc or iron with dilute hydrochloric or sulfuric acid:
Zn + 2HCl → ZnCl2 + H2
It also may be prepared by passing water vapor over heated iron:
H2O + Fe → FeO + H2
Also, it can be generated by reaction of metal hydrides with water:
CaH2 + 2H2O → Ca(OH)2 + 2H2
Another method of preparation involves heating aluminum, zinc, or otheractive metals in dilute sodium hydroxide or potassium hydroxide:
2Al + 6NaOH → 2Na3AlO3 + 3H2
Zn + 2KOH → K2ZnO2 + H2
Air & Water Reactions
Highly flammable.
Reactivity Profile
Finely divided platinum and some other metals will cause a mixture of Hydrogen and oxygen to explode at ordinary temperatures. If a jet of Hydrogen in air impinges on platinum black the metal surface gets hot enough to ignite the gases, [Mellor 1:325(1946-1947)]. Explosive reactions occur upon ignition of mixtures of nitrogen trifluoride with good reducing agents such as ammonia, Hydrogen, Hydrogen sulfide or methane. Mixtures of Hydrogen, carbon monoxide, or methane and oxygen difluoride are exploded when a spark is discharged, [Mellor 2, Supp. 1:192(1956)]. An explosion occurred upon heating 1'-pentol and 1''-pentol under Hydrogen pressure. Hydrogen appears that this acetylenic compound under certain conditions suddenly breaks down to form elemental carbon, Hydrogen, and carbon monoxide with the release of sufficient energy to develop pressures in excess of 1000 atmospheres, [AIChE Loss Prevention, p1, (1967)].
Hazard
Highly flammable and explosive, dangerous when exposed to heat or flame, explosive limits
in air 4–75% by volume.
Hazard
Hydrogen gas is very explosive when mixed with oxygen gas and touched off by a spark or flame. Many hydrides of hydrogen are dangerous and can become explosive if not stored and handled correctly. Many organic and hydrocarbon compounds are essential for life to exist, but just as many are poisonous, carcinogenic, or toxic to living organisms.
Health Hazard
Vapors may cause dizziness or asphyxiation without warning. Some may be irritating if inhaled at high concentrations. Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite. Fire may produce irritating and/or toxic gases.
Health Hazard
Hydrogen is practically nontoxic. In high concentrations this gas is a simple
asphyxiant, and ultimate loss of consciousness may occur when oxygen
Fire Hazard
EXTREMELY FLAMMABLE. Will be easily ignited by heat, sparks or flames. Will form explosive mixtures with air. Vapors from liquefied gas are initially heavier than air and spread along ground. CAUTION: Hydrogen (UN1049), Deuterium (UN1957), Hydrogen, refrigerated liquid (UN1966) and Methane (UN1971) are lighter than air and will rise. Hydrogen and Deuterium fires are difficult to detect since they burn with an invisible flame. Use an alternate method of detection (thermal camera, broom handle, etc.) Vapors may travel to source of ignition and flash back. Cylinders exposed to fire may vent and release flammable gas through pressure relief devices. Containers may explode when heated. Ruptured cylinders may rocket.
Fire Hazard
Hydrogen is a highly flammable gas that burns with an almost invisible flame and
low heat radiation. Hydrogen forms explosive mixtures with air from 4 to 75% by
volume. These explosive mixtures of hydrogen with air (or oxygen) can be ignited
by a number of finely divided metals (such as common hydrogenation catalysts). In
the event of fire, shut off the flow of gas and extinguish with carbon dioxide, dry
chemical, or halon extinguishers. Warming of liquid hydrogen contained in an
Flammability and Explosibility
Hydrogen is a highly flammable gas that burns with an almost invisible flame and
low heat radiation. Hydrogen forms explosive mixtures with air from 4 to 75% by
volume. These explosive mixtures of hydrogen with air (or oxygen) can be ignited
by a number of finely divided metals (such as common hydrogenation catalysts). In
the event of fire, shut off the flow of gas and extinguish with carbon dioxide, dry
chemical, or halon extinguishers. Warming of liquid hydrogen contained in an
enclosed vessel to above its critical temperature can cause bursting of that container.
Physiological effects
Hydrogen is nontoxic, but it can act as a simple
asphyxiant by displacing or diluting atmospheric
air to the point where the oxygen content
cannot support life. Unconsciousness without
any warning symptoms can occur from inhaling
air that contains a sufficiently large amount of
hydrogen.
storage
hydrogen cylinders should be clamped or otherwise
supported in place and used only in areas free of ignition sources and separate from
oxidizers. Expansion of hydrogen released rapidly from a compressed cylinder will
cause evolution of heat due to its negative Joule-Thompson coefficient.
Purification Methods
It is usually purified by passing through a suitable absorption train of tubes. Carbon dioxide is removed with KOH pellets, soda-lime or NaOH pellets. Oxygen is removed with a “De-oxo” unit or by passage over Cu heated to 450-500o and Cu on Kieselguhr at 250o. Passage over a mixture of MnO2 and CuO (Hopcalite) oxidises any CO to CO2 (which is removed as above). Hydrogen can be dried by passage through dried silica-alumina at -195o, through a dry-ice trap followed by a liquid-N2 trap packed with glass wool, through CaCl2 tubes, or through Mg(ClO4)2 or P2O5. Other purification steps include passage through a hot palladium thimble [Masson J Am Chem Soc 74 4731 1952], through an activated-charcoal trap at -195o, and through a non-absorbent cotton-wool filter or small glass spheres coated with a thin layer of silicone grease. Potentially VERY EXPLOSIVE in air.
Incompatibilities
Hydrogen is a reducing agent and reacts explosively with strong oxidizers such as
halogens (fluorine, chlorine, bromine, iodine) and interhalogen compounds.
Waste Disposal
Excess hydrogen cylinders should be returned to the vendor. Excess hydrogen gas present over reaction
mixtures should be carefully vented to the atmosphere under conditions of good ventilation after all
ignition sources have been removed. For more information on disposal procedures, see Chapter 7 of this
volume.
GRADES AVAILABLE
CGA G-5.3, Commodity Specification
for Hydrogen, presents the component
maxima in parts per million (v/v), unless shown
otherwise, for the types and grades of hydrogen
[1]. These are also known as quality verification
levels (QVLs). Gaseous hydrogen is denoted as
Type I, and liquefied hydrogen as Type II in the
table. A blank indicates no maximum limiting
characteristics are specified.
Check Digit Verification of cas no
The CAS Registry Mumber 1333-74-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,3,3 and 3 respectively; the second part has 2 digits, 7 and 4 respectively.
Calculate Digit Verification of CAS Registry Number 1333-74:
(6*1)+(5*3)+(4*3)+(3*3)+(2*7)+(1*4)=60
60 % 10 = 0
So 1333-74-0 is a valid CAS Registry Number.
InChI:InChI=1/H2/h1H/i1+0H
1333-74-0Relevant articles and documents
New assay method based on Raman spectroscopy for enzymes reacting with gaseous substrates
Kawahara-Nakagawa, Yuka,Nishikawa, Koji,Nakashima, Satoru,Inoue, Shota,Ohta, Takehiro,Ogura, Takashi,Shigeta, Yasuteru,Fukutani, Katsuyuki,Yagi, Tatsuhiko,Higuchi, Yoshiki
, p. 663 - 670 (2019)
Enzyme activity is typically assayed by quantitatively measuring the initial and final concentrations of the substrates and/or products over a defined time period. For enzymatic reactions involving gaseous substrates, the substrate concentrations can be estimated either directly by gas chromatography or mass spectrometry, or indirectly by absorption spectroscopy, if the catalytic reactions involve electron transfer with electron mediators that exhibit redox-dependent spectral changes. We have developed a new assay system for measuring the time course of enzymatic reactions involving gaseous substrates based on Raman spectroscopy. This system permits continuous monitoring of the gas composition in the reaction cuvette in a non-invasive manner over a prolonged time period. We have applied this system to the kinetic study of the [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F. This enzyme physiologically catalyzes the reversible oxidation of H2 and also possesses the nonphysiological functions of H/D exchange and nuclear spin isomer conversion reactions. The proposed system has the additional advantage of enabling us to measure all of the hydrogenase-mediated reactions simultaneously. Using the proposed system, we confirmed that H2 (the fully exchanged product) is concomitantly produced alongside HD by the H/D exchange reaction in the D2/H2O system. Based on a kinetic model, the ratio of the rate constants of the H/D exchange reaction (k) at the active site and product release rate (kout) was estimated to be 1.9 ± 0.2. The proposed assay method based on Raman spectroscopy can be applied to the investigation of other enzymes involving gaseous substrates.
Visible-light-driven methane formation from CO2 with a molecular iron catalyst
Rao, Heng,Schmidt, Luciana C.,Bonin, Julien,Robert, Marc
, p. 74 - 77 (2017)
Converting CO2 into fuel or chemical feedstock compounds could in principle reduce fossil fuel consumption and climate-changing CO2 emissions. One strategy aims for electrochemical conversions powered by electricity from renewable sources, but photochemical approaches driven by sunlight are also conceivable. A considerable challenge in both approaches is the development of efficient and selective catalysts, ideally based on cheap and Earth-abundant elements rather than expensive precious metals. Of the molecular photo- and electrocatalysts reported, only a few catalysts are stable and selective for CO2 reduction; moreover, these catalysts produce primarily CO or HCOOH, and catalysts capable of generating even low to moderate yields of highly reduced hydrocarbons remain rare. Here we show that an iron tetraphenylporphyrin complex functionalized with trimethylammonio groups, which is the most efficient and selective molecular electro- catalyst for converting CO2 to CO known, can also catalyse the eight-electron reduction of CO2 to methane upon visible light irradiation at ambient temperature and pressure. We find that the catalytic system, operated in an acetonitrile solution containing a photosensitizer and sacrificial electron donor, operates stably over several days. CO is the main product of the direct CO2 photoreduction reaction, but a two-pot procedure that first reduces CO2 and then reduces CO generates methane with a selectivity of up to 82 per cent and a quantum yield (light-to-product efficiency) of 0.18 per cent. However, we anticipate that the operating principles of our system may aid the development of other molecular catalysts for the production of solar fuels from CO2 under mild conditions.
Formal Kinetic Description of Photocatalytic Hydrogen Evolution from Ethanol Aqueous Solutions in the Presence of Sodium Hydroxide
Markovskaya,Kozlova
, (2018)
Abstract: The dependences of the rate of the photocatalytic hydrogen production in ethanol aqueous solutions on the concentration of ethanol and sodium hydroxide on the 1% Pt/10% Ni(OH)2/Cd0.3Zn0.7S photocatalyst under vis
Surface modification of Ni/Al2O3 with Pt: Highly efficient catalysts for H2 generation via selective decomposition of hydrous hydrazine
He, Lei,Huang, Yanqiang,Wang, Aiqin,Liu, Yu,Liu, Xiaoyan,Chen, Xiaowei,Delgado, Juan Jose,Wang, Xiaodong,Zhang, Tao
, p. 1 - 9 (2013)
Hydrous hydrazine, such as hydrazine monohydrate (N2H 4·H2O), is a promising hydrogen carrier material due to its high content of hydrogen (8.0 wt%). The decomposition of hydrous hydrazine to H2 with a high selectivity and a high activity under mild conditions is the key to its potential usage as a hydrogen carrier material. Platinum-modified Ni/Al2O3 catalysts (NiPt x/Al2O3) were prepared starting from Ni-Al hydrotalcite and tested in the decomposition of hydrous hydrazine. Compared with Ni/Al2O3, the TOF was enhanced sevenfold over NiPt 0.057/Al2O3; meanwhile, the selectivity to H2 was increased to 98%. Characterization results by means of HAADF-STEM, XRD, and EXAFS revealed the presence of surface Pt-Ni alloy in this Pt-promoted catalyst. The formation of Pt-Ni alloy could significantly weaken the interaction between adspecies produced (including H2 and NH x) and surface Ni atoms, which is confirmed by microcalorimetry and TPD results. The weakening effect could account for the greatly enhanced reaction rate, as well as H2 selectivity on NiPtx/Al 2O3 catalysts.
Tribarium tetrahedro-tetragermanide acetylenide, Ba3[Ge4][C2]: Synthesis, structure, and properties
Curda, Jan,Carrillo-Cabrera, Wilder,Schmeding, André,Peters, Karl,Somer, Mehmet,Von Schnering, Hans Georg
, p. 929 - 936 (1997)
Ba3Ge4C2 is formed at 1530 K from the elements or by reaction of BaC2 with BaGe2 (corundum crucible; steel ampoule). The compound is a semiconductor (grey colour; Eg = 1.1 eV), brittle, very sensitive to moisture, and reacts with NH4Cl at about 400 K forming acetylene and germanes up to Ge4Hn. The new Ba3Ge4C2 structure type (space group I4/mcm, No. 140; a = 8.840(1) ?, c = 12.466(1) ?; Z = 4, Pearson code tI36), contains two kinds of isolated polyanions, namely tetrahedro-tetragermanide [Ge4]4- and acetylenide [C2]2- anions. The bond lengths are d(Ge-Ge) = 2.517 ? (4x) and 2.641 ? (2x), and d(C≡C) = 1.20 ?. The Ba3[Ge4][C2] structure is a hierarchical derivative of the perovskite (CaTiO3) generated by a partial atom/cluster replacement ([Ge4] for Ca, [C2] for Ti and Ba for O). The Raman spectrum shows bands at 168, 199 and 280 cm-1, and at 1796 cm-1 characteristic for [Ge4]4- and [C2]2 polyanions, respectively.
A simple glucose route to nickel and cobalt phosphide catalysts
Zhang, Wanting,Ding, Wei,Yao, Zhiwei,Shi, Yan,Sun, Yue,Kang, Xiaoxue
, p. 826 - 831 (2021)
In this work, we have developed a simple one-step synthesis of Ni2P and CoP phosphides based on a carbonization process. The current approach uses glucose as a reductant instead of H2 and employs inert gas as feed gas. The Ni2P/C and CoP/C obtained by the glucose route showed higher CH4-CO2 reforming performance than corresponding phosphides prepared by traditional H2 reduction method, which should be attributed to the fact that the phosphides prepared by glucose route had higher surface areas and smaller particle sizes than the ones prepared by traditional method.
Photochemical In Situ Exfoliation of Metal–Organic Frameworks for Enhanced Visible-Light-Driven CO2 Reduction
Chen, Er-Xia,He, Liang,Huang, Shan-Lin,Lin, Qipu,Luo, Ming-Bu,Wei, Qin,Zheng, Hui-Li
, p. 23588 - 23592 (2021)
Two novel two-dimensional metal–organic frameworks (2D MOFs), 2D-M2TCPE (M=Co or Ni, TCPE=1,1,2,2-tetra(4-carboxylphenyl)ethylene), which are composed of staggered (4,4)-grid layers based on paddlewheel-shaped dimers, serve as heterogeneous photocatalysts for efficient reduction of CO2 to CO. During the visible-light-driven catalysis, these structures undergo in situ exfoliation to form nanosheets, which exhibit excellent stability and improved catalytic activity. The exfoliated 2D-M2TCPE nanosheets display a high CO evolution rate of 4174 μmol g?1 h?1 and high selectivity of 97.3 % for M=Co and Ni, and thus are superior to most reported MOFs. The performance differences and photocatalytic mechanisms have been studied with theoretical calculations and photoelectric experiments. This study provides new insight for the controllable synthesis of effective crystalline photocatalysts based on structural and morphological coregulation.
Effect of the preparation method of support on the aqueous phase reforming of ethylene glycol over 2 wt% Pt/Ce0.15Zr0.85O2 Catalysts
Kim, Jung-Hyun,Jeong, Kwang-Eun,Kim, Tae-Wan,Chae, Ho-Jeong,Jeong, Soon-Yong,Kim, Chu-Ung,Lee, Kwan-Young
, p. 5874 - 5878 (2013)
The effect of catalyst support on the aqueous phase reforming of ethylene glycol over supported 2 wt% Pt/Ce0.15Zr0.85O2 catalysts have been investigated. Various types of Ce0.15Zr0.85O2 mixed oxides were prepared by hydrothermal prec
Synthetic Metallodithiolato Ligands as Pendant Bases in [FeIFeI], [FeI[Fe(NO)]II], and [(μ-H)FeIIFeII] Complexes
Bhuvanesh, Nattamai,Darensbourg, Donald J.,Darensbourg, Marcetta Y.,Elrod, Lindy Chase,Ghosh, Pokhraj,Hsieh, Chung-H.,Kariyawasam Pathirana, Kavindu Dilshan
, (2020)
The development of ligands with specific stereo- and electrochemical requirements that are necessary for catalyst design challenges synthetic chemists in academia and industry. The crucial aza-dithiolate linker in the active site of [FeFe]-H2ase has inspired the development of synthetic analogues that utilize ligands which serve as conventional σ donors with pendant base features for H+ binding and delivery. Several MN2S2 complexes (M = Ni2+, [Fe(NO)]2+, [Co(NO)]2+, etc.) utilize these cis-dithiolates to bind low valent metals and also demonstrate the useful property of hemilability, i.e., alternate between bi- and monodentate ligation. Herein, synthetic efforts have led to the isolation and characterization of three heterotrimetallics that employ metallodithiolato ligand binding to di-iron scaffolds in three redox levels, (μ-pdt)[Fe(CO)3]2, (μ-pdt)[Fe(CO)3][(Fe(NO))II(IMe)(CO)]+, and (μ-pdt)(μ-H)[FeII(CO)2(PMe3)]2+ to generate (μ-pdt)[(FeI(CO)3][FeI(CO)2·NiN2S2] (1), (μ-pdt)[FeI(CO)3][(Fe(NO))II(IMe)(CO)]+ (2), and (μ-pdt)(μ-H)[FeII(CO)2(PMe3)][FeII(CO)(PMe3)·NiN2S2]+ (3) complexes (pdt = 1,3-propanedithiolate, IMe = 1,3-dimethylimidazole-2-ylidene, NiN2S2 = [N,N′-bis(2-mercaptidoethyl)-1,4-diazacycloheptane] nickel(II)). These complexes display efficient metallodithiolato binding to the di-iron scaffold with one thiolate-S, which allows the free unbound thiolate to potentially serve as a built-in pendant base to direct proton binding, promoting a possible Fe-H-···+H-S coupling mechanism for the electrocatalytic hydrogen evolution reaction (HER) in the presence of acids. Ligand substitution studies on 1 indicate an associative/dissociative type reaction mechanism for the replacement of the NiN2S2 ligand, providing insight into the Fe-S bond strength.
Photocatalytic Formic Acid Conversion on CdS Nanocrystals with Controllable Selectivity for H2 or CO
Kuehnel, Moritz F.,Wakerley, David W.,Orchard, Katherine L.,Reisner, Erwin
, p. 9627 - 9631 (2015)
Formic acid is considered a promising energy carrier and hydrogen storage material for a carbon-neutral economy. We present an inexpensive system for the selective room-temperature photocatalytic conversion of formic acid into either hydrogen or carbon monoxide. Under visible-light irradiation (λ>420 nm, 1 sun), suspensions of ligand-capped cadmium sulfide nanocrystals in formic acid/sodium formate release up to 116±14 mmolH2gcat-1h-1 with >99% selectivity when combined with a cobalt co-catalyst; the quantum yield at λ=460 nm was 21.2±2.7%. In the absence of capping ligands, suspensions of the same photocatalyst in aqueous sodium formate generate up to 102±13 mmolCOgcat-1h-1 with >95% selectivity and 19.7±2.7% quantum yield. H2 and CO production was sustained for more than one week with turnover numbers greater than 6×105 and 3×106, respectively.
