Carbon Dioxide—The Hydrogen‐Storage Material of the Future?

Enthaler, Stephan

doi:10.1002/cssc.200800101

Cited by 234 publications

(106 citation statements)

References 54 publications

(49 reference statements)

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“…However, the best results for hydrogen production reported to date have been obtained from the liquid phase decomposition of formic acid using homogeneous catalysts based on complexes of Rh (TOF=0.6 s -1 at 298 K) [38], Ru (TOF=1 s -1 at 323 K) [39,40], Fe (TOF=2.6 s -1 at 353 K) [24] or Ir (TOF=3.9 s -1 at 363 K) [41]. The highest activities obtained in our work, with a TOF value of 1 s -1 at 353 K and excellent hydrogen selectivity (>99.8%), are comparable to those for the decomposition of aqueous formic acid solutions using homogeneous catalysts.…”

Section: Discussionmentioning

confidence: 99%

Hydrogen production from formic acid vapour over a Pd/C catalyst promoted by potassium salts: Evidence for participation of buffer-like solution in the pores of the catalyst

Liu

Bulushev

Beloshapkin

et al. 2014

Applied Catalysis B: Environmental

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(D.A. Bulushev) 2 A B S T R A C T Doping a 1 wt.% Pd/C catalyst with alkali metal carbonates has a very significant promotional effect on its activity in hydrogen production from the decomposition of formic acid vapour (2 vol.%, 1 bar), potassium and caesium carbonates giving the largest effects. The K carbonate species present on the fresh catalysts react with formic acid to form formate ions, these being dissolved in a formic acid/water solution condensed in the pores of the support. The steadystate activities of the samples containing formate ions were 1-2 orders of magnitude greater than those of the unpromoted Pd/C and CO content was lower than 30 ppm. The activation energies for the reaction increased with doping from 66 to 88-99 kJ mol -1 , relatively independent of the cation of the dopant. Similar but lesser effects were found with unsupported Pd nanocrystals doped with K carbonate. The rate-determining step for the promoted samples appears to be the decomposition of formate ions on the Pd surface.

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Section: Discussionmentioning

confidence: 99%

Hydrogen production from formic acid vapour over a Pd/C catalyst promoted by potassium salts: Evidence for participation of buffer-like solution in the pores of the catalyst

Liu

Bulushev

Beloshapkin

et al. 2014

Applied Catalysis B: Environmental

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“…[1][2][3][4] In this context, one of the most significant challenges of hydrogenbased energy generation is the storage of large quantities of hydrogen at safe pressures. [1] In particular for portable applications, the use of liquid hydrogen has several disadvantages due to its continuous evaporation.…”

Section: Introductionmentioning

confidence: 99%

Decomposition of Formic Acid Catalyzed by a Phosphine‐Free Ruthenium Complex in a Task‐Specific Ionic Liquid

2010

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The dehydrogenation of formic acid is effectively catalyzed by the Ru complex [{RuCl2(p‐cymene)}2] dissolved in the ionic liquid (IL) 1‐(2‐(diethylamino)ethyl)‐3‐methylimidazolium chloride at 80 °C without additional bases. This catalytic system gives TOF values of up to 1540 h−1. Preliminary kinetic insights show formal reaction orders of 0.70(±0.15), 0.78(±0.03) and 2.00(±0.17) for the Ru catalyst, IL 1, and formic acid, respectively. The apparent activation energy of this process is estimated to be (69.1±7.6) kJ mol−1. In addition, dimeric Ru hydride ionic species involved in the reaction, such as [{Ru(p‐cymene)}2{(H)μ‐(H)‐μ‐(HCO2)}]+ and [{Ru(p‐cymene)}2{(H)μ‐(Cl)μ‐(HCO2)}]+, are identified by mass spectrometry. The presence of water in large amounts inhibits higher conversions. Finally, a remarkable catalytic activity is observed during recycles, indicating this system’s potential for hydrogen gas production.

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“…Formic acid, which is the two-electron reduction product of CO 2 , has recently attracted attention as a storage source of H 2 (1,2). Formic acid itself is an important chemical.…”

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confidence: 99%

Photocatalytic CO ₂ reduction with high turnover frequency and selectivity of formic acid formation using Ru(II) multinuclear complexes

Tamaki

Morimoto

Koike

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

292

237

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Previously undescribed supramolecules constructed with various ratios of two kinds of Ru(II) complexes-a photosensitizer and a catalyst-were synthesized. These complexes can photocatalyze the reduction of CO 2 to formic acid with high selectivity and durability using a wide range of wavelengths of visible light and NADH model compounds as electron donors in a mixed solution of dimethylformamide-triethanolamine. Using a higher ratio of the photosensitizer unit to the catalyst unit led to a higher yield of formic acid. In particular, of the reported photocatalysts, a trinuclear complex with two photosensitizer units and one catalyst unit photocatalyzed CO 2 reduction (Φ HCOOH ¼ 0.061, TON HCOOH ¼ 671) with the fastest reaction rate (TOF HCOOH ¼ 11.6 min −1 ). On the other hand, photocatalyses of a mixed system containing two kinds of model mononuclear Ru(II) complexes, and supramolecules with a higher ratio of the catalyst unit were much less efficient, and black oligomers and polymers were produced from the Ru complexes during photocatalytic reactions, which reduced the yield of formic acid. The photocatalytic formation of formic acid using the supramolecules described herein proceeds via two sequential processes: the photochemical reduction of the photosensitizer unit by NADH model compounds and intramolecular electron transfer to the catalyst unit. R ecently, global warming and shortages of fossil fuels and carbon resources have become serious issues. The development of technologies to convert CO 2 into useful organic compounds using sunlight as an energy source would serve as an ideal solution to these problems.Formic acid, which is the two-electron reduction product of CO 2 , has recently attracted attention as a storage source of H 2 (1, 2). Formic acid itself is an important chemical. It has been employed as a preservative and an insecticide and is also a useful acid, reducing agent, and source of carbon in synthetic chemical industries.Only a few photocatalysts for the selective formation of formic acid from CO 2 have been reported (3-8). Although oligo(p-phenylenes) (3) or a mixed system of phenazine and Co cyclam (4) successfully photocatalyzed the reduction of CO 2 to formic acid, these systems cannot work with visible light. It has been reported that ½RuðbpyÞ 2 ðCOÞ 2 2þ (bpy ¼ 2,2′-bipyridine) acted as a catalyst for reducing CO 2 (5-8). Under basic conditions, a mixed system of this complex with ½RuðbpyÞ 3 2þ as a redox photosensitizer photocatalyzed the reduction of CO 2 to formic acid with high selectivity (6, 8). However, this photocatalytic system is limited by instability as evidenced by the fact that the catalyst decomposed following prolonged irradiation and generated black precipitates.We have recently developed a unique architecture for constructing visible-light-driven supramolecular photocatalysts, consisting of a ½RuðN ∧ NÞ 3 2þ (N ∧ N ¼ a diimine ligand)-type complex as a photosensitizer and a Re(I) diimine complex as a catalyst (9-12). These supramolecules can selectively photocatalyze ...

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Carbon Dioxide—The Hydrogen‐Storage Material of the Future?

Cited by 234 publications

References 54 publications

Hydrogen production from formic acid vapour over a Pd/C catalyst promoted by potassium salts: Evidence for participation of buffer-like solution in the pores of the catalyst

Hydrogen production from formic acid vapour over a Pd/C catalyst promoted by potassium salts: Evidence for participation of buffer-like solution in the pores of the catalyst

Decomposition of Formic Acid Catalyzed by a Phosphine‐Free Ruthenium Complex in a Task‐Specific Ionic Liquid

Photocatalytic CO ₂ reduction with high turnover frequency and selectivity of formic acid formation using Ru(II) multinuclear complexes

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Carbon Dioxide—The Hydrogen‐Storage Material of the Future?

Cited by 234 publications

References 54 publications

Hydrogen production from formic acid vapour over a Pd/C catalyst promoted by potassium salts: Evidence for participation of buffer-like solution in the pores of the catalyst

Hydrogen production from formic acid vapour over a Pd/C catalyst promoted by potassium salts: Evidence for participation of buffer-like solution in the pores of the catalyst

Decomposition of Formic Acid Catalyzed by a Phosphine‐Free Ruthenium Complex in a Task‐Specific Ionic Liquid

Photocatalytic CO 2 reduction with high turnover frequency and selectivity of formic acid formation using Ru(II) multinuclear complexes

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Photocatalytic CO ₂ reduction with high turnover frequency and selectivity of formic acid formation using Ru(II) multinuclear complexes