Dehydrogenation of ammonia-borane by cationic Pd(<scp>ii</scp>) and Ni(<scp>ii</scp>) complexes in a nitromethane medium: hydrogen release and spent fuel characterization

Kim, Sung‐Kwan; Hong, Seok-In; Son, Ho‐Jin; Han, Won‐Sik; Michalak, Artur; Hwang, Son‐Jong; Kang, Sang Ook

doi:10.1039/c5dt00599j

Cited by 11 publications

(7 citation statements)

References 47 publications

(32 reference statements)

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“…Many homogeneous catalyst systems dehydrogenate AB nonhydrolytically; these include complexes of iron, molybdenum, iridium, rhodium, nickel, palladium, and ruthenium (Figure ). A limited number of homogeneous metal catalysts can produce two equivalents of H 2 and even fewer can surpass this two equivalent mark …”

Section: Introductionmentioning

confidence: 99%

Ruthenium-Catalyzed Ammonia Borane Dehydrogenation: Mechanism and Utility

et al. 2016

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One of the greatest challenges in using H as a fuel source is finding a safe, efficient, and inexpensive method for its storage. Ammonia borane (AB) is a solid hydrogen storage material that has garnered attention for its high hydrogen weight density (19.6 wt %) and ease of handling and transport. Hydrogen release from ammonia borane is mediated by either hydrolysis, thus giving borate products that are difficult to rereduce, or direct dehydrogenation. Catalytic AB dehydrogenation has thus been a popular topic in recent years, motivated both by applications in hydrogen storage and main group synthetic chemistry. This Account is a complete description of work from our laboratory in ruthenium-catalyzed ammonia borane dehydrogenation over the last 6 years, beginning with the Shvo catalyst and resulting ultimately in the development of optimized, leading catalysts for efficient hydrogen release. We have studied AB dehydrogenation with Shvo's catalyst extensively and generated a detailed understanding of the role that borazine, a dehydrogenation product, plays in the reaction: it is a poison for both Shvo's catalyst and PEM fuel cells. Through independent syntheses of Shvo derivatives, we found a protective mechanism wherein catalyst deactivation by borazine is prevented by coordination of a ligand that might otherwise be a catalytic poison. These studies showed how a bidentate N-N ligand can transform the Shvo into a more reactive species for AB dehydrogenation that minimizes accumulation of borazine. Simultaneously, we designed novel ruthenium catalysts that contain a Lewis acidic boron to replace the Shvo -OH proton, thus offering more flexibility to optimize hydrogen release and take on more general problems in hydride abstraction. Our scorpionate-ligated ruthenium species (12) is a best-of-class catalyst for homogeneous dehydrogenation of ammonia borane in terms of its extent of hydrogen release (4.6 wt %), air tolerance, and reusability. Moreover, a synthetically simplified ruthenium complex supported by the inexpensive bis(pyrazolyl)borate ligand is a comparably good catalyst for AB dehydrogenation, among other reactions. In this Account, we present a detailed, concise description of how our work with the Shvo system progressed to the development of our very reactive and flexible dual-site boron-ruthenium catalysts.

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Section: Introductionmentioning

confidence: 99%

Ruthenium-Catalyzed Ammonia Borane Dehydrogenation: Mechanism and Utility

et al. 2016

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Section: Resultsmentioning

confidence: 99%

“…The carbon doping into FeBO 3 can also be visualized through the formation of iron carbonyl (Fe-C=O) bonding between 1900 cm −1 and 2100 cm −1 (Figure3). The other distinct IR band at 2500 cm −1 is assigned to the hydride vibration of borane (B-H)[38,39].The XPS analysis of the as-prepared C,N-doped FeBO 3 is presented in Figure4. Here, the XPS survey spectrum (Figure4a) confirms the presence of the elements B, C, N, O, and Fe, with the significant percentage of C and N further confirming the successful doping (TableS1).…”

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confidence: 99%

Facile Synthesis of Carbon- and Nitrogen-Doped Iron Borate as a Highly Efficient Single-Component Heterogeneous Photo-Fenton Catalyst under Simulated Solar Irradiation

2021

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The development of a heterogeneous catalyst for use in environmental remediation remains a challenging and attractive research endeavor. Specifically, for Fenton reactions, most research approaches have focused on the preparation of iron-containing heterostructures as photo-Fenton catalysts that utilize visible light for enhancing the degradation efficiency. Herein, the synthesis and novel application of C,N-doped iron borates are demonstrated as single-component heterogeneous photo-Fenton catalysts with high Fenton activity under visible light. Under the optimal conditions, 10 mg of the catalyst is shown to achieve effective degradation of 10 ppm methylene blue (MB) dye, Rhodamine B (RhB) dye, and tetracycline (TC) under simulated solar irradiation with a first-order rate constant of k = 0.218 min−1, 0.177 min−1, and 0.116 min−1, respectively. Using MB as a model system, the C,N-doped iron borate exhibits 10- and 26-fold increases in catalytic activity relative to that of the 50 nm hematite nanoparticles and that of the non-doped iron borate, respectively, in the presence of H2O2 under the simulated solar irradiation. Furthermore, the optimum reaction conditions used only 320 equivalents of H2O2 with respect to the concentration of dye, rather than the several thousand equivalents of H2O2 used in conventional heterogeneous Fenton catalysts. In addition, the as-prepared C,N-doped iron borate achieves 75% MB degradation after 20 min in the dark, thus enabling the continuous degradation of pollutants at night and in areas with poor light exposure. The stability and recyclability of C,N-doped iron borate for the oxidation of MB was demonstrated over three cycles with insignificant loss in photo-Fenton activity. The high Fenton activity of the C,N-doped iron borate is considered to be due to the synergistic action between the negatively-charged borate ligands and the metal center in promoting the Fenton reaction. Moreover, carbon and nitrogen doping are shown to be critical in modifying the electronic structure and increasing the conductivity of the catalyst. In view of its synthetic simplicity, high efficiency, low cost of reagents, and minimal cost of operation (driven by natural sunlight), the as-prepared heterogeneous single-component metal borate catalyst has potential application in the industrial treatment of wastewater.

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“…1 Although catalytic hydrolysis is well known and efficient for H 2 production from AB, 2 non-hydrolytic dehydrogenation is a more desirable approach, because it (1) enables more facile re-reduction of dehydrogenated spent fuel3 and (2) minimizes evolution of ammonia, a hydrogen fuel cell poison, in the eluent gas stream. 4, 1b Several transition metal catalysts are active for non-hydrolytic AB dehydrogenation, including complexes of iron, 5 molybdenum, 6 iridium, 7 rhodium, 8 nickel, 9 palladium, 10 and ruthenium. 11, 12 Catalyst systems reported to date fit one of two classes: 13 (1) those that release 1 equivalent of hydrogen quickly 14, 7 and (2) those that release 2 or more equivalents slowly.…”

Section: Introductionmentioning

confidence: 99%

“…11, 12 Catalyst systems reported to date fit one of two classes: 13 (1) those that release 1 equivalent of hydrogen quickly 14, 7 and (2) those that release 2 or more equivalents slowly. 9, 10a, 12, 15 The latter are known to proceed through (or stop at) borazine, N 3 B 3 H 6 , as an intermediate with its subsequent conversion to polyborazylene as a slow step in the overall mechanism of hydrogen evolution. 16 This is problematic because (1) slow borazine derivatization limits H 2 productivity, 12 (2) borazine, which boils at 55 ºC, is poisonous to fuel cells, and (3) borazine is known to coordinate metals 17 and deactivate some AB dehydrogenation catalysts.…”

Section: Introductionmentioning

confidence: 99%

Dehydrogenation of ammonia borane through the third equivalent of hydrogen

2016

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Ammonia Borane (AB) has high hydrogen density (19.6 wt. %), and can, in principle, release up to 3 equivalents of H2 under mild catalytic conditions. A limited number of catalysts are capable of non-hydrolytic dehydrogenation of AB beyond 2 equivalents of H2 under mild conditions, but none of these is shown directly to derivatise borazine, the product formed after 2 equivalents of H2 are released. We present here a high productivity ruthenium-based catalyst for non-hydrolytic AB dehydrogenation that is capable of borazine dehydrogenation, and thus exhibits among the highest H2 productivity reported to date for anhydrous AB dehydrogenation. At 1 mol% loading, (phen)Ru(OAc)2(CO)2 (1) effects AB dehydrogenation through 2.7 equivalents of H2 at 70°C, is robust through multiple charges of AB, and is water and air stable. We further demonstrate that catalyst 1 has the ability both to dehydrogenate borazine in isolation and dehydrogenate AB itself. This is important, both because borazine derivatisation is productivity-limiting in AB dehydrogenation and because borazine is a fuel cell poison that is commonly released in H2 production from this medium.

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Dehydrogenation of ammonia-borane by cationic Pd(ii) and Ni(ii) complexes in a nitromethane medium: hydrogen release and spent fuel characterization

Cited by 11 publications

References 47 publications

Ruthenium-Catalyzed Ammonia Borane Dehydrogenation: Mechanism and Utility

Ruthenium-Catalyzed Ammonia Borane Dehydrogenation: Mechanism and Utility

Facile Synthesis of Carbon- and Nitrogen-Doped Iron Borate as a Highly Efficient Single-Component Heterogeneous Photo-Fenton Catalyst under Simulated Solar Irradiation

Dehydrogenation of ammonia borane through the third equivalent of hydrogen

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