Catalyst For Dehydrogenation Of Formic Acid Research Articles

Study of Non-Noble-Metal-Based Metal–Nitrogen–Carbon Catalysts for Formic Acid Dehydrogenation

Study of Non-Noble-Metal-Based Metal–Nitrogen–Carbon Catalysts for Formic Acid Dehydrogenation

Green hydrogen storage and delivery: Utilizing highly active homogeneous and heterogeneous catalysts for formic acid dehydrogenation

Significant technological revolution which allows the use of hydrogen as an efficient energy carrier and mitigates the use of fossil fuels is a crucial need of the day. Much attention has been paid to cope with the recent, reversible, and sustainable hydrogen storage technologies. Among recent strategies, formic acid (FA) has been marked as an efficient liquid chemical for hydrogen storage. The liquid organic hydrogen carriers are based on some vital characteristics that particularly reduce toxicity and consist of maximum hydrogen with efficient recyclability. This review summarizes the recent reports, studies, and investigations concerning the hydrogen production from dehydrogenation of FA, which is almost free of carbon monoxide and is considered as an excellent material in fuel cell (FC) technology. A comprehensive critical review is carried out to link the latest research progress for subsequent achievements and to investigate both the homogeneous and heterogeneous catalysts. Among these catalysts, the main focus is on precious and non-precious metals that have been progressively increased during the past decade. Furthermore, the recent developments in the generation of high-pressure hydrogen gas and its practical applications have been highlighted for better understanding. • Formic acid selected as sustainable and efficient liquid chemical for H 2 storage. • CO free H 2 production from dehydrogenation of formic acid. • Recent development in generation of high-pressure H 2 .

Nitrogen-phosphorus co-functionalized reduced graphene oxide supported NiCoPd-CeOx nanoparticles as a highly efficient and stable catalyst for formic acid dehydrogenation

Formic acid (HCOOH, FA), a common liquid hydrogen storage material, has attracted tremendous research interest. However, the development of efficient, low-cost and high-stable heterogeneous catalyst for selective dehydrogenation of FA remains a major challenge. In this paper, a simple co-reduction method is proposed to synthesize nitrogen-phosphorus co-functionalized rGO (NPG) supported ultrafine NiCoPd-CeO x nanoparticles (NPs) with a mean size of 1.2 nm. Remarkably, the as-prepared Ni 0.2 Co 0.2 Pd 0.6 -CeO x /NPG shows outstanding catalytic activity for FA dehydrogenation, affording a high TOF value of 6506.8 mol H 2 mol Pd −1 h −1 at 303 K and a low activation energy of 17.7 kJ mol −1 , which is better than most of the reported heterogeneous catalysts, and can be ascribed to the combined effect of well-dispersed ultrafine NiCoPd-CeO x NPs, modified Pd electronic structure, and abundant active sites. The reaction mechanism of dehydrogenation of FA is also discussed. Furthermore, the optimized Ni 0.2 Co 0.2 Pd 0.6 -CeO x /NPG shows excellent stability over 10 th run with 100% conversion and 100% H 2 selectivity, which may provide more possibilities for practical application of FA system on fuel cells. • N–P co-functionalized rGO supported ultrafine NiCoPd-CeO x NPs are successfully synthesized via a simple co-reduction method. • NPG has a positive effect on improving the distribution and controlling particle size. • The Ni 0.2 Co 0.2 Pd 0.6 -CeO x /NPG exhibits high activity towards FA dehydrogenation, giving a TOF of 6506.8 h −1 at 303 K. • The Ni 0.2 Co 0.2 Pd 0.6 -CeO x /NPG shows excellent stability and activity even after 10 th run.

Efficient solventless dehydrogenation of formic acid by a CNC-based rhodium catalyst

A CNC based rhodium complex is an efficient catalyst for formic acid dehydrogenation under solventless conditions.

Bimetallic PdCo Nanoparticles Loaded in Amine Modified Polyacrylonitrile Hollow Spheres as Efficient Catalysts for Formic Acid Dehydrogenation

Polyacrylonitrile hollow nanospheres (HPAN), derived from the polymerization of acrylonitrile in the presence of polystyrene emulsion (as template), were modified by surface amination with ethylenediamine (EDA), and then used as support for loading Pd or PdCo nanoparticles (NPs). The resultant bimetallic catalyst (named PdCo0.2/EDA-HPAN) can efficiently catalyze the additive-free dehydrogenation of formic acid with very high activity, selectivity and recyclability, showing turnover frequencies (TOF) of 4990 h−1 at 333 K and 915 h−1 at 303 K, respectively. The abundant surface amino groups and cyano group as well as the hollow structure of the support offer a suitable environment for achieving high dispersion of the Pd-based NPs on the surface of EDA-HPAN, thus generating ultra-small bimetallic NPs (bellow 1.0 nm) with high stability. The addition of a small portion of Co may adjust the electronic state of Pd species to a certain extent, which can further improve their capability for the dehydrogenation of formic acid. In addition, the surface amino groups may also play an important role in synergistically activating formic acid to generate formate, thus leading to efficient conversion of formic acid to hydrogen at mild conditions.

Control of Catalyst Isomers Using an N-Phenyl-Substituted RN(CH2CH2PiPr2)2 Pincer Ligand in CO2 Hydrogenation and Formic Acid Dehydrogenation.

A novel pincer ligand, iPrPNPhP [PhN(CH2CH2PiPr2)2], which is an analogue of the versatile MACHO ligand, iPrPNHP [HN(CH2CH2PiPr2)2], was synthesized and characterized. The ligand was coordinated to ruthenium, and a series of hydride-containing complexes were isolated and characterized by NMR and IR spectroscopies, as well as X-ray diffraction. Comparisons to previously published analogues ligated by iPrPNHP and iPrPNMeP [CH3N(CH2CH2PiPr2)2] illustrate that there are large changes in the coordination chemistry that occur when the nitrogen substituent of the pincer ligand is altered. For example, ruthenium hydrides supported by the iPrPNPhP ligand always form the syn isomer (where syn/anti refer to the relative orientation of the group on nitrogen and the hydride ligand on ruthenium), whereas complexes supported by iPrPNHP form the anti isomer and complexes supported by iPrPNMeP form a mixture of syn and anti isomers. We evaluated the impact of the nitrogen substituent of the pincer ligand in catalysis by comparing a series of iPrPNRP (R = H, Me, Ph)-ligated ruthenium hydride complexes as catalysts for formic acid dehydrogenation and carbon dioxide (CO2) hydrogenation to formate. The iPrPNPhP-ligated species is the most active for formic acid dehydrogenation, and mechanistic studies suggest that this is likely because there are kinetic advantages for catalysts that operate via the syn isomer. In CO2 hydrogenation, the iPrPNPhP-ligated species is again the most active under our optimal conditions, and we report some of the highest turnover frequencies for homogeneous catalysts. Experimental and theoretical insights into the turnover-limiting step of catalysis provide a basis for the observed trends in catalytic activity. Additionally, the stability of our complexes enabled us to detect a previously unobserved autocatalytic effect involving the base that is added to drive the reaction. Overall, by modifying the nitrogen substituent on the MACHO ligand, we have developed highly active catalysts for formic acid dehydrogenation and CO2 hydrogenation and also provided a framework for future catalyst development.

Amine-functionalized carbon nanotubes supported NiAuPd nanoparticles as an efficient in-situ prepared catalyst for formic acid dehydrogenation

Hydrogen (H2) generation from formic acid (FA) decomposition is a promising route in practical application of hydrogen energy. As a promising H2 supplier, besides the advantage of high H2 content and excellent stability, FA can also be used as a mild reducing agent. Herein, an in-situ prepared NiAuPd nanoparticles (NPs) supported on amine-functionalized carbon nanotubes (NiAuPd/NH2-CNTs) with FA as the reducing agent is successfully developed at room temperature. The as-prepared NiAuPd/NH2-CNTs are directly used for the catalytic decomposition of FA, exhibiting excellent activity and 100% H2 selectivity with the initial turnover frequency (TOFinitial) value of 699.1 and 3006.1 mol H2 mol Pd-1 h-1 at 303 and 333 K, respectively. Moreover, the additive sodium formate (SF) can further facilitate the reduction process and enhance the catalytic performance, with the TOFinitial value of 4391.1 mol H2 mol Pd-1 h-1 at 333 K, which are comparable to most of the reported heterogeneous catalysts with the complicated post-treatment. The excellent catalytic performance of NiAuPd/NH2-CNTs is mainly attributed to the high dispersion of NPs and the boost effect of -NH2 group on O–H cleavage. This work provides a feasible strategy to design in-situ prepared catalysts for the efficient high-quality H2 generation from FA for fuel cells application.

Yolk-shell silica dioxide spheres @ metal-organic framework immobilized Ni/Mo nanoparticles as an effective catalyst for formic acid dehydrogenation at low temperature

The novel catalyst with yolk-shell SiO2 NiMo/SiO2 spheres immobilized by zeolitic imidazolate framework (ZIF-67) materials has been successfully prepared. The experimental results indicated that the prepared catalyst exhibits superior performance for hydrogen generation from Formic acid (FA) dehydrogenation without any additives at low temperatures. The catalytic performances of the NixMo1−x/ZIF-67@SiO2 yolk-shell increased with Ni addition ratio increasing. In this research, Ni0.8Mo0.2/ZIF-67@SiO2 yolk-shell could provide the highest catalytic conversion efficiency. This is due to the uniform dispersion of fine metal nanoparticles (NPs) and synergistic effect between the NiMo NPs and ZIF-67@SiO2 supporter. The turn over frequency (TOF) value was approximately 13,183 h−1 at 25 °C through complete FA conversion. H2 selectivity was also approximately 100% with obvious CO-free hydrogen production at 25 °C. Meanwhile, the prepared NiMo/ZIF-67@SiO2 yolk-shell catalyst also shows superior catalytic stability with corresponding 99% activity after 10 cycles. In summary, the catalyst preparation and hydrogen generated from FA dehydrogenation obtained from this research could provide the important information for application in catalyst innovation and waste FA recycling and recovery in the future.

Efficient Iridium Catalysts for Formic Acid Dehydrogenation: Investigating the Electronic Effect on the Elementary β-Hydride Elimination and Hydrogen Formation Steps

We report herein a series of Cp*Ir complexes containing a rigid 8-aminoquinolinesulfonamide moiety as highly efficient catalysts for the dehydrogenation of formic acid (FA). The complex [Cp*Ir(L)Cl] (HL = N-(quinolin-8-yl)benzenesulfonamide) displayed a high turnover frequency (TOF) of 2.97 × 104 h-1 and a good stability (>100 h) at 60 °C. Comparative studies of [Cp*Ir(L)Cl] with the rigid ligand and [Cp*Ir(L')Cl] (HL' = N-propylpypridine-2-sulfonamide) without the rigid aminoquinoline moiety demonstrated that the 8-aminoquinoline moiety could dramatically enhance the stability of the catalyst. The electron-donating ability of the N,N'-chelating ligand was tuned by functionalizing the phenyl group of the L ligand with OMe, Cl, and CF3 to have a systematical perturbation of the electronic structure of [Cp*Ir(L)Cl]. Experimental kinetic studies and density functional theory (DFT) calculations on this series of Cp*Ir complexes revealed that (i) the electron-donating groups enhance the hydrogen formation step while slowing down the β-hydride elimination and (ii) the electron-withdrawing groups display the opposite effect on these reaction steps, which in turn leads to lower optimum pH for catalytic activity compared to the electron-donating groups.

Understanding the Deactivation Pathways of Iridium(III) Pyridine-Carboxiamide Catalysts for Formic Acid Dehydrogenation.

The degradation pathways of highly active [Cp*Ir(κ2 -N,N-R-pica)Cl] catalysts (pica=picolinamidate; 1 R=H, 2 R=Me) for formic acid (FA) dehydrogenation were investigated by NMR spectroscopy and DFT calculations. Under acidic conditions (1 equiv. of HNO3 ), 2 undergoes partial protonation of the amide moiety, inducing rapid κ2 -N,N to κ2 -N,O ligand isomerization. Consistently, DFT modeling on the simpler complex 1 showed that the κ2 -N,N key intermediate of FA dehydrogenation (INH ), bearing a N-protonated pica, can easily transform into the κ2 -N,O analogue (INH2 ; ΔG≠ ≈11 kcal mol-1 , ΔG ≈-5 kcal mol-1 ). Intramolecular hydrogen liberation from INH2 is predicted to be rather prohibitive (ΔG≠ ≈26 kcal mol-1 , ΔG≈23 kcal mol-1 ), indicating that FA dehydrogenation should involve mostly κ2 -N,N intermediates, at least at relatively high pH. Under FA dehydrogenation conditions, 2 was progressively consumed, and the vast majority of the Ir centers (58 %) were eventually found in the form of Cp*-complexes with a pyridine-amine ligand. This likely derived from hydrogenation of the pyridine-carboxiamide via a hemiaminal intermediate, which could also be detected. Clear evidence for ligand hydrogenation being the main degradation pathway also for 1 was obtained, as further confirmed by spectroscopic and catalytic tests on the independently synthesized degradation product 1 c. DFT calculations confirmed that this side reaction is kinetically and thermodynamically accessible.

One-step synthesis of Ni@Pd/NH2-Fe3O4 nanoparticles as affordable catalyst for formic acid dehydrogenation

Currently, one of the critical issues in the world is finding an appropriate green alternative to fossil fuels due to the concerns about global warming. As a hydrogen source, formic acid has been given particular attention owing to the attractive features such as high-energy density, no toxicity, high stability at ambient temperature and high hydrogen content. Introducing an affordable and highly efficient catalyst with easy recovery from the reaction mixture for selective dehydrogenation of formic acid is still demanding. In this report, we used a simple one-step process to synthesize Ni@Pd core shell nanoparticles on 3-aminopropyltriethoxysilane modified Fe 3 O 4 nanoparticles. The existence of Ni and Pd results in a synergic effect on the catalytic activity. The NH 2 groups play an important role for obtaining well-dispersed ultrafine particles with high surface area and active sites. In addition, Fe 3 O 4 lead to convenient magnetic recovery of the catalyst from reaction mixture. Our results indicate that the as-prepared catalyst give the superb turnover frequency of 5367.8 h −1 with no additive, which is higher than most of the previously reported catalysts.

Bimetallic PdAu catalysts for formic acid dehydrogenation

A series of monometallic and bimetallic palladium gold catalyst were prepared and studied for the formic acid dehydrogenation reaction. Different Pd/Au compositions were employed (PdxAu100-x, where x = 25; 50 and 75) and their impact on alloy structure, particle size and dispersion was evaluated. Active phase composition and reaction parameters such as temperature, formic acid concentration or formate/formic acid ratio were adjusted to obtain active and selective catalyst for hydrogen production. An important particle size effect was observed and related to Pd/Au composition for all bimetallic catalysts.

Pd/UIO-66/sepiolite: Toward highly efficient dual-supported Pd-based catalyst for dehydrogenation of formic acid at room temperature

Formic acid (FA) has come to be considered as a potential material for chemical storage of hydrogen. Despite tremendous efforts, the development of highly efficient and relatively low-cost heterogeneous catalysts for dehydrogenation of FA remains a major challenge; the weak recyclability of catalyst limits its application in industry. In this work, the synthesis of Pd nanoparticles immobilized on UIO-66 amino grafting sepiolite (SEP) dual supports is by an impregnation-reduction method. The UIO-66 framework on fibrous amine-functionalized SEP support can significantly prevent agglomeration during the dehydrogenation process and control the size of Pd nanoparticles. The sacrificial effect of Pd nanoparticles from UIO-66 enables the active sites on NH2-SEP to maintain consistent catalytic activity and reusability in additive-free FA solution over 8th recycled use. Compared to current catalyst systems, this catalyst offers a brighter prospect of novel and efficient heterogeneous catalysis for formic acid dehydrogenation.

Amine-functionalized sepiolite: Toward highly efficient palladium nanocatalyst for dehydrogenation of additive-free formic acid

Formic acid has recently come to be considered as a promising material for chemical storage of hydrogen. To date, highly efficient and low-cost heterogeneous catalysts for formic acid dehydrogenation without additive under mild conditions are still limited. In this work, we employed amine-functionalized sepiolite, a typical natural clay mineral with fibrous structure, as support to synthesize a nanocatalyst by the simple impregnation-reduction method. The amine groups on amine functionalized sepiolite support are shown to significantly reduce the average size of Pd nanoparticles (from 7.60 to 2.80 nm) as well as provide a synergistic effect with the Pd nanoparticles, which boosts the rate of additive-free formic acid dehydrogenation (initial turnover frequency (TOF) values of 5587 h−1 at 60 °C, equal to or even better than the most active heterogeneous catalysts). Compared to current catalyst systems, this catalyst can lead to a brighter prospect of cost-efficient heterogeneous catalysts for formic acid dehydrogenation.

Synergistic Cu2 Catalysts for Formic Acid Dehydrogenation.

Hexanuclear copper hydride complexes, [Cu6(μ3-H)2( meso-L4)3(RNC)4](PF6)4 (R = tBu (6a), Cy (6b)), were prepared by using a new linear tetraphosphine, meso-Ph2PCH2P(Ph)(CH2)4P(Ph)CH2PPh2 ( meso-L4), and were converted into active catalysts of [Cu2(μ-O2CH)( meso-L4)(RNC)2]+ under the reaction conditions of formic acid dehydrogenation, where unsymmetric dinuclear copper sites supported by the tetradentate phosphine and isocyanide ligands were essential to demonstrate effective catalytic activity.

Computationally guided design of a new Rh catalyst for selective formic acid dehydrogenation: Validation with caution

Formic acid possesses many desirable properties as a promising hydrogen energy carrier. Density functional theory (DFT) was utilized to design new Rh complexes with 2,2′-biimidazoline ligands to explore their potential as catalysts for formic acid dehydrogenation. These designed complexes were prepared and examined as catalysts under various temperatures and ratios of formic acid to sodium formate. It was found that although our complexes gave a high TOF of 20,000 h−1 at 90 °C under certain formic acid/sodium formate ratios, the dehydrogenation reaction was prematurely deactivated once 30% of the formic acid was consumed. Possible deactivation mechanisms were investigated by NMR and HRMS. Our observations suggest that while guided rational design of catalysts by DFT has much potential, the method does have limitations as evidenced by our experimental comparisons and thus pure DFT design should be conducted with caution.

Dehydrogenation of Formic Acid Catalyzed by Water‐Soluble Ruthenium Complexes: X‐ray Crystal Structure of a Diruthenium Complex

Dehydrogenation of formic acid over various Ru‐arene complexes containing N‐donor chelating ligands was investigated in H2O and isolated and characterized several important catalytic intermediate species to elucidate the reaction pathway for formic acid dehydrogenation. Among the studied complexes, Ru‐arene complexes, namely [(η6‐C6H6)Ru(κ2‐NpyNH2‐AmQ)Cl]+ (C‐2), [(η6‐C10H14)Ru(κ2‐NpyNH2‐AmQ)Cl]+ (C‐3) and [(η6‐C6H6)Ru(κ2‐NpyNHMe‐MAmQ)Cl]+ (C‐4) [AmQ = 8‐aminoquinoline and MAmQ = 8‐(N‐methylamino)quinoline] were proved to be the efficient catalysts for formic acid dehydrogenation at 90 °C, even in the absence of base. With an initial TOF of 940 h–1, complex C‐4 displayed the highest catalytic activity for formic acid dehydrogenation in H2O and it can be recycled up to 5 times with a TON of 2248. Effect of temperature, pH, formic acid and catalyst concentration on the reaction kinetics were also investigated in detail. Extensive mechanistic investigations using mass spectrometry and NMR evidenced the formation of a coordinatively unsaturated species [(η6‐C6H6)Ru(κ2‐NpyNH‐AmQ)]+ (C‐2A)/[(η6‐C6H6)Ru(κ2‐NpyNMe‐MAmQ)]+ (C‐4A) as the active component during the catalytic dehydrogenation of formic acid. We further characterized the dimer‐form of C‐2A, possibly the catalyst resting state, by single‐crystal X‐ray crystallography.

Ni anchored C2N monolayers as low-cost and efficient catalysts for hydrogen production from formic acid

Noble-metal-free catalysts are highly desirable for hydrogen generation from formic acid dehydrogenation. Herein, using first-principles density functional theory calculations, we design a series of nickel-anchored nitrogenated holey two-dimensional carbon structures (Nix@C2N, x = 1–3) as formic acid dehydrogenation catalysts. For all Nix@C2N surfaces, the formic acid dehydrogenation preferably proceeds via the formate pathway. The effective barrier continuously decreases for formic acid dehydrogenation while increases for hydrogen formation from Ni1@C2N to Ni3@C2N. The side reaction producing carbon monoxide and water via the carboxyl or formyl pathway cannot occur on Ni1@C2N or Ni2@C2N and is not preferred on Ni3@C2N, and thus, the Nix@C2N catalysts possess excellent selectivity of hydrogen. Notably, the unsaturated nitrogen atom of substrate also participates in the reaction and exhibits synergetic effect with the nickel component in Ni1@C2N and Ni2@C2N. The Gibbs free energetic span analysis predicts that the order of reactivity is Ni2@C2N (0.79 eV) > Ni1@C2N (0.87 eV) > Ni3@C2N (1.23 eV), and the turnover frequency of Nix@C2N is evaluated. The results are compared with the experimental and theoretical reports of some palladium-based catalysts. The present work suggests that the Nix@C2N may be promising noble-metal-free catalysts for formic acid dehydrogenation with high performance and low cost.

Superior activity of Pd nanoparticles confined in carbon nanotubes for hydrogen production from formic acid decomposition at ambient temperature

Designing highly efficient and low-cost catalysts is essential toward realizing the practical application of hydrogen generation by formic acid decomposition (FAD) under ambient conditions. Herein, we report the synthesis of a hybrid material of Pd nanoparticles encapsulated within carbon nanotubes (CNTs) (Pd-CNTs-in). Transmission electron microscopy images show that most Pd nanoparticles (mean diameter 4.2 ± 0.8 nm) are located inside the nanotubes. Temperature-programmed reduction studies of H2 reveal that the average reduction temperature of the Pd(II) species adsorbed on the interior wall of the CNTs is 12 °C lower than those adsorbed on the outer walls of the CNT. Moreover, the as-prepared Pd-CNTs-in catalysts show extremely high FAD activity and durability at ambient temperature. The turn over frequency (TOF) value is as high as 1135 h−1 for the initial 10 min and does not decay significantly during the consecutive 3-time recycling studies. X-Ray photoelectron spectroscopy (XPS), surface-enhanced infrared spectroscopy (SEIRAS), and gas chromatography (GC) studies indicate that CNT confinement induced electronic structure modulation of Pd could be the major reason for the enhancement of FAD catalysis on the Pd-CNTs-in surface. This work could provide promising strategies for the fabrication of cost-effective and high-active Pd-based catalysts for formic acid dehydrogenation.

Super Nanoteragonal ZrO2 Embedded in Carbon as Efficient Support of PdAg Nanoparticle for Boosting Hydrogen Generation from Formic Acid

AbstractThe application of formic acid (FA) as a safe, renewable and promising hydrogen‐storage material has received considerable attention. However, exploring efficient heterogeneous catalysts for selective dehydrogenation of FA remains a challenging topic. In this paper, a super nanoteragonal ZrO2 (The crystallite size reached even 150 nm) is synthesized by calcining Zr‐based metal‐organic framework. Because the unique microstructures of the material which possess the electron‐rich property and surface basicity, the resulting PdAg@ZrO2/C catalyst exhibits excellent activity (Turnover frequency 9206 h−1 at 50 °C) for the decomposition of FA. These results may contribute to the design of efficient catalysts for dehydrogenation of FA and extended applications of tetragonal zirconia polycrysta without the dopants or reduction of the crystallite size.