Formic Acid Dehydrogenation Reaction Research Articles

On the Demise of PPP-Ligated Iron Catalysts in the Formic Acid Dehydrogenation Reaction.

The PPP-ligated iron complexes, cis-(iPrPPRP)FeH2(CO) [iPrPPRP = (o-iPr2PC6H4)2PR (R = H or Me)], catalyze the dehydrogenation of formic acid to carbon dioxide but lose their catalytic activity over time. This study focuses on the analysis of the species formed from the degradation of cis-(iPrPPMeP)FeH2(CO) over its course of catalyzing the dehydrogenation reaction. These degradation products include species both soluble and insoluble in the reaction medium. The soluble component of the decomposed catalyst is a mixture of cis-[(iPrPPMeP)FeH(CO)2][(HCO2)(HCO2H)x], protonated iPrPPMeP, and oxidation products resulting from adventitious O2. The precipitate is solvated Fe(OCHO)2. Further mechanistic investigation suggests that cis-[(iPrPPMeP)FeH(CO)2][(HCO2)(HCO2H)x] displays diminished but measurable catalytic activity, likely through the displacement of a CO ligand by the formate ion. The formation of Fe(OCHO)2 along with the dissociation of iPrPPMeP is responsible for the eventual loss of catalytic activity.

Formic acid dehydrogenation reaction on high-performance PdxAu1−x alloy nanoparticles prepared by the eco-friendly slow synthesis methodology

Formic acid dehydrogenation reaction on high-performance PdxAu1−x alloy nanoparticles prepared by the eco-friendly slow synthesis methodology

New 3D Printing Strategy for Structured Carbon Devices Fabrication

This work shows a new method for the preparation of 100% carbon-structured devices. The method is based on resorcinol-formaldehyde polymerization, using starch as a binder with the addition of a certain amount of external carbon source before polymerization. Molds obtained by 3D printing are used to shape the structured devices in the desired shape, and the ultimate pyrolysis step consolidates and produces the carbonaceous devices. The proposed method allows obtaining supports with different textural and surface properties varying the carbonaceous source, the solvent, or the pyrolysis conditions, among other factors. The as-obtained devices have demonstrated their usefulness as palladium supports for the gas-phase formic acid dehydrogenation reaction. The monolith shows a high conversion of formic acid (81% according to H2 production) and a high selectivity towards hydrogen production at mild temperatures (80% at 423 K).

Formic Acid Dehydrogenation over a Monometallic Pd and Bimetallic Pd:Co Catalyst Supported on Activated Carbon

In this study, palladium is proposed as an active site for formic acid dehydrogenation reaction. Pd activity was modulated with Co metal with the final aim of finding a synergistic effect that makes possible efficient hydrogen production for a low noble metal content. For the monometallic catalysts, the metal loadings were optimized, and the increase in the reaction temperature and presence of additives were carefully considered. The present study aimed, to a great extent, to enlighten the possible routes for decreasing noble metal loading in view of the better sustainability of hydrogen production from liquid organic carrier molecules, such as formic acid.

Diruthenium Catalyst for Hydrogen Production from Aqueous Formic Acid

Diruthenium complexes [{(η6-arene)RuCl}2(μ-κ2:κ2-benztetraimd)]2+ containing the bridging bis-imidazole methane-based ligand {1,4-bis(bis(2-ethyl-5-methyl-1H-imidazol-4-yl)methyl)benzene} (benztetraimd) are synthesized for catalytic formic acid dehydrogenation in water at 90 °C. Catalyst [{(η6-p-cymene)RuCl}2(μ-κ2:κ2-benztetraimd)]2+ [1-Cl2] exhibited a remarkably high turnover frequency (1993 h-1 per Ru atom) and long-term stability over 60 days for formic acid dehydrogenation, while the analogous (η6-benzene)diruthenium and mononuclear catalysts displayed low activity with poor long-term stability. Notably, catalyst [1-Cl2] also displayed an appreciably high turnover number of 93 200 for the bulk-scale reaction. In addition, the in-depth mass and nuclear magnetic resonance investigations under the catalytic and control experimental conditions revealed the active involvement of several crucial catalytic intermediate species, such as Ru-aqua species [{(η6-p-cymene)Ru(H2O)}2(μ-L)]2+ [1-(OH2)2], Ru-formato species [{(η6-p-cymene)Ru(HCOO)}2(μ-L)] [1-(HCOO)2], and Ru-hydrido species [{(η6-p-cymene)Ru(H)}2(μ-L)] [1-(H)2], in the catalytic formic acid dehydrogenation reaction.

Anchoring PdAg nanoparticles on ZIF-67-derived Co@NC composite as a catalyst for efficient hydrogen evolution from formic acid

A facile wet-chemical method was utilized to graft the PdxAg1-x alloy nanoparticles on the Co@NC composites derived from ZIF-67 by carbonization at different temperatures. The characterization results verified that the carbonization temperature exhibits a marked influence on the physical properties of the Co@NC composites. The surface area increased with temperature, ensuring the high dispersion of the PdAg alloy nanoparticles on the surface of the Co@NC composites. The performance evaluation of the dehydrogenation reaction of formic acid showed that the PdAg alloy nanoparticles deposited on Co@NC obtained at a carbonization temperature of 900 °C exhibited the highest activity. The catalytic performance of PdAg/Co@NC catalysts towards H2 generation was strongly related to the composition of the PdAg alloy and followed the trend of Pd2Ag1/Co@NC > Pd1Ag1/Co@NC > Pd9Ag1/Co@NC > Pd/Co@NC > Pd1Ag2/Co@NC. The residual metallic Co in the carbon matrix is somewhat beneficial to improving the catalytic activity and stability of the catalyst.

Chromic hydroxide-decorated palladium nanoparticles confined by amine-functionalized mesoporous silica for rapid dehydrogenation of formic acid.

Formic acid (FA), one of the products of biomass conversion and CO2 reduction, has attracted much attention as a renewable liquid hydrogen carrier with a high hydrogen content (4.4wt%). Searching for efficient catalysts to realize hydrogen evolution from FA are highly desired but challenging. Herein, ultrafine and mono-dispersed Pd-Cr(OH)3 nanoparticles (1.3nm) loaded on amine-functionalized mesoporous silica (AFMS) have been prepared and applied as an effective catalyst for rapid hydrogen production from additive-free FA. The as-synthesized Pd-Cr(OH)3/AFMS catalysts exhibited efficient catalytic activity and 100% hydrogen selectivity and conversion toward FA dehydrogenation reaction without additives, giving an initial TOF value of 3112h-1 at 323K, which is comparable to most of the highly efficient heterogeneous catalysts reported so far under similar reaction conditions. This work provides a feasible idea for the design metal hydroxide-modified Pd-based efficient heterogeneous catalyst, which is expected to enhance the application of FA in fuel cells.

Cyclic Amide-Anchored NHC-Based Cp*Ir Catalysts for Bidirectional Hydrogenation–Dehydrogenation with CO2/HCO2H Couple

H2 storage in carbon dioxide (CO2) or bicarbonate (HCO3–) in the form of formic acid (HCO2H) or formate (HCO2–) and the reverse H2 liberation allows, in principle, to develop a rechargeable hydrogen carrier system along with a CO2-recycling mechanism. The key to such an alluring approach toward the realization of a carbon-neutral H2-based fuel option is the development of efficient bidirectional catalysts for CO2 (or HCO3–) hydrogenation and HCO2H (or HCO2–) dehydrogenation. With an aim toward (i) structurally robust catalysts under variable reaction conditions, (ii) metal–ligand bifunctionality-triggered heterolytic H2 splitting and H+/H– transfer during hydrogenation/dehydrogenation reactions, (iii) electron-rich catalytic metal center for facilitating hydride delivery, and (iv) water solubility of the catalysts via second coordination sphere interactions, herein, we applied a series of “cyclic amide–NHC” hybrid bidentate ligand-bound Cp*Ir(III) complexes (Ir-1–Ir-4) in bidirectional hydrogenation–dehydrogenation of CO2 (HCO3–)/HCO2H (HCO2–) couple in water as a “green” solvent without the use of organic additives/solvents. Notably, with the catalyst Ir-1, hydrogenation of CO2 achieving a turnover number (TON) of 16 680 at 60 °C in 6 h and dehydrogenation of formic acid with a turnover frequency (TOF5min) of 70 674 h–1 at 80 °C can be efficiently carried out. Key control and mechanistic studies emphasized the following aspects of the current system: (i) pH of the solution played a crucial role in controlling the rate of hydrogenation/dehydrogenation reactions, (ii) H2 was cleaved readily by the catalyst to form the iridium hydride intermediate, which could react with CO2 to furnish the formate product, (iii) pH (acid/base)-switchable on-demand formic acid dehydrogenation was devised, and (iv) the liberated H2 and CO2 gas from the Ir-1-catalyzed formic acid dehydrogenation reaction were reutilized in secondary reactions in a tandem fashion, signifying the suitability of the system to demonstrate the utility of formic acid as a typical H2/CO2 storage liquid, as it is advocated for.

The rational design of a graphitic carbon nitride-based dual S-scheme heterojunction with energy storage ability as a day/night photocatalyst for formic acid dehydrogenation

Photocatalytic formic acid dehydrogenation (FAD) has been regarded as one of the most promising methods of producing H2 in a sustainable manner. In the photocatalytic FAD reaction, photogenerated holes play an important role in the reaction mechanism and thus in the efficiency of photocatalysts. However, the design of photocatalytic systems capable of generating high hole potential without compromising the reducing ability of the photocatalyst is extremely rare for the FAD reaction. In this respect, we report herein a novel and highly efficient heterojunction photocatalyst composed of 2D graphitic carbon nitride, 2D MnO2, 1D MnOOH, and 0D PdAg alloy nanoparticles, denoted as GCN/MnO2/MnOOH-PdAg, that can create high reduction and oxidation potentials via a dual S-scheme heterojunction. The photocatalysts exhibited a superb photocatalytic activity in the FAD with a record turnover frequency (TOF) of 3919 h−1 under visible light irradiation, which was 6-, 5.2- and 24-times greater than those of GCN-PdAg, GCN/MnO2-PdAg, and MnO2/MnOOH-PdAg heterojunctions, respectively. The structure and dual S-scheme mechanism of the photocatalyst have been clearly demonstrated by extensive instrumental analysis, radical trapping tests, and scavenger experiments. More importantly, it was discovered that the presented photocatalyst continued to function with comparable activity in dark for a prolonged time using the same photocatalytic mechanism. The activity of the photocatalyst in dark was attributed to the utilization of electrons stored on Mn2O3, which was detected as a 4–5 nm thick layer on the surface of MnOOH nanorods. This study, in addition to being the first example of both a “day/night photocatalyst” for FAD with an S-scheme mechanism, also demonstrates for the first time the boosting of FAD via a dual S-scheme heterojunction photocatalyst.

Ultrafine Pd nanoparticles on amine-functionalized carbon nanotubes for hydrogen production from formic acid

Formic acid is a promising hydrogen source and liquid organic hydrogen carrier because of its high hydrogen density. To produce hydrogen from formic acid, catalytic dehydrogenation of formic acid over Pd-based catalysts has been investigated. Here, a highly active catalyst is rationally designed. Carbon nanotubes without micropores were adopted as a support to facilitate the mass transport of reactants or products. Pd particles were made as small as possible to provide a large number of active sites and to alleviate the activation barrier for hydrogen desorption. Amine functional groups were introduced into carbon nanotubes to generate formate anions by capturing protons from formic acid. Based on this design, ultrafine Pd nanoparticles (1.76 nm) on amine-functionalized carbon nanotubes were successfully synthesized. This catalyst demonstrated remarkable activity for the formic acid dehydrogenation reaction, with a high turnover frequency value of 2560 h−1 at 30 °C.

Hydroxyl bond activation of formic acid by Metal-ligand cooperation of new designed aluminum ligated pincer fullerenes

• New designed aluminum ligated NNN pincer fullerene. • Aluminum-ligand cooperation ►►OH bond cleavage HCOOH. • H 2 elimination ►►protonation of imine carbon atom. • The aluminum complex with three HCOO►► active catalyst. • Catalytic cycle►► β-hydride elimination to dissociate CO 2 . The two parts of the formic acid dehydrogenation reaction including catalyst activation and catalytic cycle with a new designed aluminum ligated NNN pincer fullerene as catalyst in which Al(III)–bis(imino)pyridyl pincer are located on the (6, 6) ring fusion bond of C 60 fullerene was investigated with density functional calculations. Aluminum-ligand cooperation enables O H bond cleavage of formic acid in the HCOOH-assisted H 2 elimination pathway with protonation of imine carbon atom. The aluminum complex with three HCOO – units (complex 8 ) forms the active catalyst of HCOOH dehydrogenation. The existences of hydrogen bonds in the studied molecules were confirmed by NBO and AIM analyses. In the catalytic cycle, β-hydride elimination from 8 to dissociate CO 2 and formation of Al–H complex promote HCOOH dehydrogenation to generate H 2 . The β-hydride elimination is the rate-determining step with an overall barrier of +17.8 kcalmol −1 . The effect of fullerene cage on the catalytic cycle of HCOOH dehydrogenation is explored by elimination of fullerene cage from the Al(III)– bis(imino)pyridyl pincer fullerene.

Structure-sensitivity of formic acid dehydrogenation reaction over additive-free Pd NPs supported on activated carbon

In this study the size-activity dependence of palladium based catalysts in formic acid dehydrogenation reaction was investigated and evaluated. A wide range of particle sizes was considered and the catalyst series were prepared upon variation of some synthetic parameters, precursor and solvent nature in particular. Synthesis method variations affect significantly Pd particle size and results in diverse activity toward hydrogen production. An optimal size was observed and explained by the diverse proportion of low and high coordinated Pd states available for different samples within the series. The evaluation of particles much bigger than 6 nm changes importantly the fraction of high and low coordination atoms and allows the clear confirmation of the importance of the presence of low coordination atoms on the surface of catalyst.

Mechanistic insights on aqueous formic acid dehydrogenation over Pd/C catalyst for efficient hydrogen production

Efficient hydrogen production is one of the most important issues in the future energy economy. Dehydrogenation of formic acid has been extensively investigated for safe and easy hydrogen production. Thereby, various catalysts have been developed for aqueous formic acid dehydrogenation (FAD) reaction to efficiently produce hydrogen. However, there is still a lack of understanding of the reaction mechanism. Herein, to fundamentally comprehend the aqueous FAD reaction mechanism, we prepared Pd/C catalyst and performed controlled catalytic tests. The results demonstrated that the aqueous FAD reaction occurs through the formate anion dehydrogenation pathway. DFT calculation explained this by the observation that the charge of formate anion significantly mitigates the activation barrier of H-COO bond cleavage. In addition, computational prediction combined with kinetic isotope effect experiments verified that combinative desorption of hydrogen is the rate-determining step of FAD.

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.

NH3 plasma synthesis of N-doped activated carbon supported Pd catalysts with high catalytic activity and stability for HCOOH dehydrogenation

Plasma is a simple and effective method to prepare N-doped carbon materials and supported metal catalysts. In this work, Pd/C–C(NH3) and Pd/C–P(NH3) catalysts are prepared by heat treatment and cold plasma methods using Ar and NH3 as the working gas. The activity and stability of obtained catalysts are tested by formic acid dehydrogenation reaction. The results show that TOFinitial of Pd/C–P(NH3) is 527.1 h−1 at 50 °C, and the HCOOH decomposition rate is about 89.2% at 4 h. The hydrogen production of Pd/C–P(NH3) when used in first and third cycle are 1.14 and 1.14 times than that of Pd/C–C(NH3), and 1.24 and 13.24 times than that of commercial Pd/C. Various characterization techniques are used to characterize the structure of the prepared Pd/C catalysts. The results indicate that NH3 plasma is milder than NH3 thermal treatment. The high activity and stability of Pd/C–P(NH3) are mainly due to the NH3 cold plasma effectively achieving N-doping of the carbon support, and Pd nanoparticles with a small size and high dispersion. Atmospheric pressure NH3 cold plasma provides an effective method to prepare high-performance Pd/C catalysts for HCOOH dehydrogenation and plays a guiding role in the preparation of high-performance carbon-supported noble metal catalysts.

MWCNT-Supported PVP-Capped Pd Nanoparticles as Efficient Catalysts for the Dehydrogenation of Formic Acid.

Various carbon materials were used as support of polyvinylpyrrolidone (PVP)-capped Pd nanoparticles for the synthesis of catalysts for the production of hydrogen from formic acid dehydrogenation reaction. Among investigated, MWCNT-supported catalysts were the most promising, with a TOF of 1430 h−1 at 80°C. The presence of PVP was shown to play a positive role by increasing the hydrophilicity of the materials and enhancing the interface contact between the reactant molecules and the catalytic active sites.

Facile synthesis of PdAu/C by cold plasma for efficient dehydrogenation of formic acid

Decomposition of formic acid biomass to generate hydrogen is vital for coping with fossil energy depletion, environmental pollution, and developing clean, efficient, safe, and sustainable modern energy system. In this study, a PdAu/C−C bimetallic catalyst was prepared by the co-impregnation method followed by an atmospheric pressure (AP) cold plasma treatment to synthesize PdAu/C−P catalysts. The resulting PdAu/C−P showed excellent catalytic activity for the formic acid dehydrogenation (FAD) reaction. The total volume of H2 and CO2 released from the FAD reaction was about 375 mL after 4 h at 50 °C, and the initial turnover frequency (TOFinitial) was 808.6 h−1. We used X−ray diffractometry (XRD), temperature programmed reduction (TPR) and high-resolution transmission electron microscopy (HRTEM) to show that plasma can effectively promote the redispersion of Pd−Au particles on the surface of the support. The average particle size of PdAu/C−P (3.5 ± 1.5 nm) was less than PdAu/C−C (4.4 ± 1.9 nm) and uniformly distributed. X-ray photoelectron spectroscopy (XPS), TPR, and HRTEM showed that PdAu/C−P has a higher degree of alloying. In addition, the strong electric field in the plasma facilitated more metal sites located on the outer surface of the support in PdAu/C−P, and the atomic ratio of M/C (M = Pd and Au) (0.0134) was much larger than that of PdAu/C−C (0.0060). The apparent activation energy (Ea) of PdAu/C−P for the FAD reaction was only 27.25 kJ mol−1, and it had much higher activity and stability than the commercial Pd/C (Sigma−Aldrich). The total volume of H2 and CO2 produced over the PdAu/C−P for three cycles was 1.33, 5.87, and 8.56 times that of commercial Pd/C. Overall, the cold plasma enhanced the degree of alloying, promoted the redispersion of agglomerated particles, and regulated the surface enrichment of the active metal components. This is of great significance for guiding the preparation of high−performance multi-metal catalysts by cold plasma.

Formic Acid Dehydrogenation by Ruthenium Catalyst – Computational and Kinetic Analysis with the Energy Span Model

The ruthenium (cis‐RuCl2(DPPM)2) based catalytic dehydrogenation reaction of formic acid in the presence of an amine base in a biphasic system experimentally tested by Treigerman and Sasson (ChemistrySelect 2017, 2, 5816) was studied computationally to ascertain its mechanism. The energy span model was applied on the double‐hybrid DFT computed energy profile to comprehend its kinetics. The catalytic network includes three possible interconnected cycles depending on the ancillary ligands, going through decarboxylation, protonation and H2 release. The dihydride cycle proves to be the most efficient after pre‐activation steps coming from the other cycles. The turnover frequency (TOF) determining intermediate (TDI) is the formatohydride species, while the TOF determining transition state (TDTS) corresponds to a formate decarboxylation. Herein we include the effect of reactants concentrations to the energy span model, which proved to be essential to comprehend the experimental ESI‐MS results and to propose a more accurate mechanism.

Pd-CNT-SiO2 nanoskein: composite structure design for formic acid dehydrogenation.

High energy density and low toxicity of formic acid makes it a promising hydrogen energy carrier. Here we report a Pd/CNT-based formic acid dehydrogenation catalyst that shows a significant decrease in the apparent activation energy compared to benchmark Pd catalysts and provide a mechanistic insight into its catalytic performance.

Enhanced formic acid dehydrogenation by the synergistic alloying effect of PdCo catalysts supported on graphitic carbon nitride

The catalytic ability of graphitic carbon nitride (g-C3N4)-supported composition-controlled PdCo catalysts towards H2 generation from the formic acid dehydrogenation reaction was assessed in this study and a noticeable composition dependence was evidenced. It was seen that the alloying effect combined with the nitrogen functionalities present on g-C3N4 assisted the formation of small and well-distributed nanoparticles. This fact, combined with the electronic promotion of Pd species via charge transfer from Co and basic features of the support, resulted in enhanced catalytic activities compared to that displayed by the counterpart Pd/g-C3N4, reaching a TOF value of 1193 h−1 for the most active catalyst among investigated (PdCo/g-C3N4 (1/0.7)). Furthermore, the present catalytic system showed high selectivity towards formic acid dehydrogenation, suppressing the generation of undesired CO via formic acid dehydration, which makes it a suitable candidate for practical application in fuel cells.