Dehydrogenation Of Formic Acid Research Articles

Aluminum fluoride induced PdAu nanoparticles on layered g-C3N4 nanosheets for efficient dehydrogenation of formic acid at room temperature

We first develop the aluminum fluoride-induction strategy to construct PdAu nanoparticles combined with layered g-C3N4 nanosheets (g-CNNS) by two-dimensional (2D) template approach. During the calcination process, g-CNNS are formed in the interlayer space of layered clay montmorillonite (MMT) template using melamine as precursor. After removing the MMT template by hydrofluoric acid, well-defined g-CNNS are obtained, accompanied by the formation of aluminum fluoride. Under the presence and induction of aluminum fluoride, PdAu alloy nanoparticles are uniformly dispersed on the surface of g-CNNS through the simple reduction process. Well-defined catalyst (PdAu/g-CNNS-AlF3) exhibits high catalytic performance for the decomposition of formic acid to hydrogen at room temperature, such as high catalytic activity (TOF: 2716 h−1) and high hydrogen selectivity (100%). These excellent catalytic activities are ascribed to the high specific surface area, unique 2D nanosheets architecture, and uniformly dispersed PdAu nanoparticles. This AlF3-induced strategy combined with 2D-template approach provides a new idea for the design of highly efficient heterogeneous catalysts.

Tuning dehydrogenation behavior of formic acid on boosting cell performance of formic acid fuel cell at elevated temperatures

In high-temperature formic acid fuel cell (HT-FAFC), the dehydrogenation behavior of formic acid plays a significant role in boosting cell output performance by leading to a favorable and powerful hydrogen oxidation reaction (HOR) on the anode side instead of the direct formic acid oxidation reaction (dFAOR). The formic acid dehydrogenation mechanism of HT-FAFC at 200 °C is investigated by regulating concentration and flow rate. As a competitive path of dehydrogenation, unfavorable dehydration occurs simultaneously accompany by carbon monoxide (CO) release. It is found that high formic acid concentration is conducive to the dehydrogenation to produce more hydrogen, however, the reduction of water vapor content may promote the dehydration reaction and result in the inhibition of dehydrogenation. As the non-preferable alternative, the dehydration-caused total CO release remains under CO maximum tolerance (3%) of Pt catalyst at 200 °C which is unlikely to affect the power output of HT-FAFC. The permeation of formic acid can be considered as a barrier when the high concentration exceeds 12 mol L−1 or the flow rate exceeds 1 mL min−1. These findings may deepen understanding of formic acid consuming behavior of HT-FAFC anode, which helps to formulate strategies to improve cell performance in general.

N-doped carbon layer-coated Au nanocatalyst for H2-free conversion of 5-hydroxymethylfurfural to 5-methylfurfural

Deoxygenative upgrading of 5-hydromethylfurfural (HMF) into valuable chemicals has attracted intensive research interest in recent years, with product selectivity control remaining an important topic. Herein, TiO2 supported gold catalysts coated with a thin N-doped porous carbon (NPC) layer were developed via a polydopamine-coating-carbonization strategy and utilized for pathway-specific conversion of HMF into 5-methylfurfural (5-MF) with the use of renewable formic acid (FA) as the deoxygenation reagent. The as-fabricated Au/TiO2@NPC exhibited excellent catalytic performance with a high yield of 5-MF (>95%). The catalytic behavior of [email protected] catalysts was shown to be correlated with the suitable combination of highly dispersed Au nanoparticles and favorable interfacial interactions in the [email protected] core-shell hetero-nanoarchitectures, thereby facilitating the preferential esterification of HMF with FA and suppressing unproductive FA dehydrogenation, which promoted the selective formylation/decarboxylation of hydroxy-methyl group in HMF in a pathway-specific manner. The present NPC/metal interfacial engineering strategy may provide a potential guide for the rational design of advanced catalysts for a wide variety of heterogeneous catalysis processes in terms of the conversion of biomass source.

In situ reduction of PdO encapsulated in MCM-41 to Pd(0) for dehydrogenation of formic acid

A series of PdO@MCM-41-x was in situ synthesized by a facile one-pot method, and their catalytic performance for dehydrogenation of formic acid was investigated. The PdO nanoparticles were immobilized in MCM-41 channel with small size of 2.2–2.5 nm due to the confinement of mesoporous silica. The initial turnover frequency (TOF) of as-prepared catalyst can reach 1096 h−1 at 323 K with 100% hydrogen selectivity. The hydrogen production activity was better than that of catalyst priorly reduced by hydrogen because of the gradual reduction of PdO nanoparticles and generation of fresh Pd(0) during the formic acid dehydrogenation process, which was confirmed by XPS characterization and catalytic system monitoring. It provides a new way for the preparation of simple and efficient catalysts for hydrogen production, which has great application potential.

Amine-Functionalized Natural Halloysite Nanotubes Supported Metallic (Pd, Au, Ag) Nanoparticles and Their Catalytic Performance for Dehydrogenation of Formic Acid

In today’s age of resource scarcity, the low-cost development and utilization of renewable energy, e.g., hydrogen energy, have attracted much attention in the world. In this work, cheap natural halloysite nanotubes (HNTs) were modified with γ-aminopropyltriethoxysilane (APTES), and the functionalized HNTs were used as to support metal (Pd, Au, Ag) catalysts for dehydrogenation of formic acid (DFA). The supports and fabricated catalysts were characterized with ICP, FT-IR, XRD, XPS and TEM. The functional groups facilitate the anchoring of metal particles to the supports, which brings about the high dispersion of metallic particles in catalysts. The catalysts show high activity against DFA and exhibit selectivity of 100% toward H2 at room temperature or less. The interactions between active centers and supports were investigated by evaluation and comparison of the catalytic performances of Pd/NH2-HNTs, PdAg/NH2-HNTs and PdAu/NH2-HNTs for DFA.

Iron Dihydride Complex Stabilized by an All-Phosphorus-Based Pincer Ligand and Carbon Monoxide.

PNP-pincer-stabilized iron carbonyl dihydride complexes are key intermediates in catalytic hydrogenation and dehydrogenation reactions; however, decomposition through these intermediates has been observed. This inspires the development of a PPP-pincer system that may show improved catalyst stability. In this work, bis[2-(diisopropylphosphino)phenyl]phosphine (or iPrPPHP) is used to react with FeCl2 under a carbon monoxide (CO) atmosphere to yield trans-(iPrPPHP)Fe(CO)Cl2. A subsequent reaction with NaBH4 produces syn/anti-(iPrPPHP)FeH(CO)Cl or cis,anti-(iPrPPHP)Fe(CO)H2, depending on the amount of NaBH4 employed. The cis-dihydride complex shows catalytic activity for the conversion of PhCHO to PhCH2OH (under H2) or PhCO2CH2Ph (under Ar). It also catalyzes the dehydrogenation of PhCH2OH to PhCHO and PhCO2CH2Ph, albeit with limited turnover numbers. A more efficient catalytic process is the dehydrogenation of formic acid to carbon dioxide (CO2), which can operate under additive-free conditions. Mechanistic investigation suggests that the cis-dihydride complex undergoes protonation with formic acid to release H2 while forming anti-(iPrPPHP)FeH(CO)(OCHO)·HCO2H, in which the CO ligand has shifted and the formate is hydrogen-bonded to formic acid. The hydrido formate complex loses CO2 under ambient conditions, completing the catalytic cycle by reforming the cis-dihydride complex.

Single-Site Iridium Picolinamide Catalyst Immobilized onto Silica for the Hydrogenation of CO2 and the Dehydrogenation of Formic Acid.

The development of an efficient heterogeneous catalyst for storing H2 into CO2 and releasing it from the produced formic acid, when needed, is a crucial target for overcoming some intrinsic criticalities of green hydrogen exploitation, such as high flammability, low density, and handling. Herein, we report an efficient heterogeneous catalyst for both reactions prepared by immobilizing a molecular iridium organometallic catalyst onto a high-surface mesoporous silica, through a sol–gel methodology. The presence of tailored single-metal catalytic sites, derived by a suitable choice of ligands with desired steric and electronic characteristics, in combination with optimized support features, makes the immobilized catalyst highly active. Furthermore, the information derived from multinuclear DNP-enhanced NMR spectroscopy, elemental analysis, and Ir L3-edge XAS indicates the formation of cationic iridium sites. It is quite remarkable to note that the immobilized catalyst shows essentially the same catalytic activity as its molecular analogue in the hydrogenation of CO2. In the reverse reaction of HCOOH dehydrogenation, it is approximately twice less active but has no induction period.

Modification of Pd Nanoparticles with Lower Work Function Elements for Enhanced Formic Acid Dehydrogenation and Trichloroethylene Dechlorination.

Catalytic degradation of halogenated contaminants by palladium (Pd) is a promising technology for environmental remediation. However, the low utilization of H by Pd catalyst and its easy poisoning prevent its applications. Here, low work function elements (B or Ag) were incorporated into Fe@C-supported Pd nanoparticles (NPs) to alter their crystalline structure and induce electronic effects, addressing these issues. The Pd mass-normalized dechlorination rates of trichloroethylene (TCE) by Fe@C-Pd-B and Fe@C-Pd-Ag were 51 and 59 times higher than that of unmodified Fe@C-Pd, respectively. The H utilization efficiency of Fe@C-Pd-B and Fe@C-Pd-Ag was 5.4 and 7.2 times higher than that of unmodified Fe@C-Pd, respectively. Various characterizations suggest that the B or Ag incorporation induced the charge redistribution and elevated the electron density of Pd atoms, resulting in the enhanced formic acid (FA) dehydrogenation and TCE dechlorination. Although the Ag incorporation presented a relatively higher H utilization due to the suppressed combination of H and accumulation of unsaturated hydrocarbons (i.e., C2H4), the Fe@C-Pd-Ag was easily deactivated. In contrast, the B incorporation enabled the Pd NPs with a good stability. These findings can guide the rational design of robust Pd-based catalysts for efficient and selective FA dehydrogenation and chlorinated contaminant degradation.

Effects of doping a boron atom in g-C3N4 on the catalytic activity of deposited Pd atom for the dehydrogenation of formic acid: A DFT study

The catalytic performance of palladium atom deposited on the cavity of the g-C3N4 sheet for the formic acid (FA) dehydrogenation was investigated using M06-L calculations. For the Pd1/g-C3N4 system, the preferable pathway for H2 production from FA decomposition occurs through the hydrocarboxyl intermediate with Ea of 21.2 kcal mol−1 for the rate-determining step (RDS). For B-doped g-C3N4, two different forms, which are the substitution of a boron atom at the nitrogen or the carbon atom, were used to examine the impact of the support on the catalytic activity of the deposited Pd atom. The boron dopant can enhance the basicity of the g-C3N4. As a result. the deposited Pd atom becomes more positively charged as compared to that on the pristine support. The greater the positive charge of the Pd atom, the stronger interaction with FA is found. Furthermore, the enhancement of basicity of the B-doped g-C3N4 sheet plays a key role in activating the O-H bond of FA as compared to that on the bare support. The reaction mechanism on Pd1/B-doped g-C3N4 favorably proceeds through the formate pathway. The activation energy of RDS is predicted to be 11.4 and 16.4 kcal mol−1 for BN-, BC-doped g-C3N4 supports, respectively.

Heterogeneous Catalysis for Carbon Dioxide Mediated Hydrogen Storage Technology Based on Formic Acid

AbstractIn the context of global carbon dioxide increasing drastically, renewable energy is crucial maintain the economic growth of the world. Hydrogen has attracted considerable attention as a clean fuel, but the large‐scale storage and controllable release of H2 is still urgently needed, yet largely not yet accomplished. Through the reactions of CO2 hydrogenation to formic acid (FA) and FA dehydrogenation to hydrogen, a “carbon neutral” sustainable hydrogen storage system can be constructed. With advantages of excellent recyclability and facile separation for heterogeneous catalysis, developing efficient heterogeneous catalysts for hydrogen storage based on FA is the primary focus of this review, mainly involving metal catalysts from nanoscale to single‐atom scale. Firstly, the effects of metal size on the catalytic activities are highlighted in detail. Additionally, special attention is paid to the relevant structure–activity relationships of various supported catalysts and the mechanistic insights, which can provide a theoretical foundation for rational catalyst design. This review brings new and systemic insights into innovative and efficient heterogeneous catalysts design and applications for the ultimate FA‐based sustainable hydrogen storage system with a closed carbon loop.

Unveiling the mechanistic landscape of formic acid dehydrogenation catalyzed by Cp∗M(III) catalysts (M = Co or Rh or Ir) with bis(pyrazol-1-yl)methane ligand architecture: A DFT investigation

The production of dihydrogen via formic acid dehydrogenation (FAD) has been gaining remarkable attention and advancement as an alternative, sustainable and clean energy source. Density functional theory (DFT) calculations have been utilized to probe the reaction mechanism of FAD catalyzed by a Cp∗Rh(III) complex reported by Fink and Laurenczy with bis(pyrazol-1-yl)methane ligand system. The calculated energetics show that the rate-limiting step is the β-hydride elimination step and protonation by hydronium ion was calculated to be the most favourable route requiring relatively less activation energy than the conventional process which entails formic acid as the proton source. The Co and Ir congeners of the chosen Rh catalyst were computationally designed and they were also found to follow the same mechanism. Interestingly, the three metal centres (Co, Rh and Ir) were estimated to possess nearly the same activation barrier of c.a. 14 kcal/mol at the rate determining step. Thus, the proposed Co complex with such a small rate determining activation barrier, could be considered as a cheap and propitious earth-abundant transition metal-based catalyst for FAD.

Hydrogen generation over Ni@Pd NCs through an active H-exchange from formic acid-water system

The use of Formic acid as an alternative to fossil fuels is promising, both from economical and ecological standpoints, and has received great of attention owing to its inherently superiority in recent decades. Nevertheless, efficient and low-cost solid catalyst for formic acid dehydrogenation at room temperature still constitutes a biggish challenge. Moreover, comparing to increase the catalytic performance of catalysts, very little attention payed to the kinetic mechanism of dehydrogenation reaction because of the lack of effective characterization artifice. Here, the as-prepared Ni@Pd nanoparticles by a sequential reduction process can be useful catalyst for formic acid decomposition at room temperature without a promoter. Thanks to the effective catalyst and isotope distribution technique, preliminary mechanistic results firstly reveal that hydrogen is obtained via a H-atom recombination on isolated sites after the proton exchange randomly between activated H and solvent.

In situ observation of photo-induced shortening of single Au nanorod for plasmon-enhanced formic acid dehydrogenation

Photo-induced selective shortening strategy was developed to synthesize Au nanorods (NRs) with different aspect ratios, and in situ observation of photo-induced shortening of single Au nanorod was realized, which is helpful for understanding the relationship between SPR decay and geometric nanostructure. The as-synthesized plasmonic Pd–Au NRs exhibit efficient formic acid dehydrogenation. Very impressively, the interfacial interaction between plasmonic bimetallic nanostructures and adsorbed molecules (HCOOH) was explored in situ at the single-particle level. Significant photoluminescence (PL) quenching of Pd–Au NRs was observed when HCOOH contacted the catalyst, confirming the charge transfer between Pd–Au NRs and HCOOH molecules. Finally, we shed light on the catalytic mechanism of plasmon-induced HCOOH dehydrogenation by coupling single-particle PL measurement with finite difference time domain (FDTD) and density functional theory (DFT) calculations.

The role of CeO2 morphology on dehydrogenation from formic acid over Pd/CeO2 catalysts

Formic acid as a potential hydrogen carrier has received increasing attention. The catalyst used for the dehydrogenation of formic acid is the key to the process. In this paper, a series of Pd/CeO2 catalyzed dehydrogenation of formic acid were prepared by controlling the morphology of CeO2. CeO2 with diverse morphologies had different specific surface area, the number of Ce electronic states and oxygen vacancies, which could influence the chemical environment and dispersion of Pd species. The as-synthesized Pd/CeO2-H (hollow sphere) exhibited high catalytic activity with a turnover frequency (TOF) value of 870 h−1 at 50 °C.

Dehydrogenation of formic acid mediated by a Phosphorus–Nitrogen PN3P-manganese pincer complex: Catalytic performance and mechanistic insights

The utilization of formic acid as a liquid organic hydrogen carrier has taken a vast interest lately because of several desirable properties. The state-of-the-art homogenous catalysts known for formic acid dehydrogenation are mainly based on noble metals such as iridium or ruthenium. 3d metals are considered to be an attractive alternative due to their abundance and low toxicity. Exploration of 3d metals has achieved exciting results mainly with iron-based catalysts; however, manganese has not received much attention, and only a few examples are available. Here we report a manganese complex [Mn(PN3P)(CO)2]Br containing a pincer backbone, as an efficient catalyst for formic acid dehydrogenation. Under the optimized condition, the complex afforded a TON of 15,200. To the best of our knowledge, this is considered one of the best TON achieved using a manganese-based complex with excellent selectivity. Mechanistic studies suggested that the imine arm participates in the formic acid activation/deprotonation step, emphasizing the importance of metal-ligand cooperativity during substrate activation to promote catalytic efficacy.

Defect-dominated carbon deposited Pd nanoparticles enhanced catalytic performance of formic acid dehydrogenation

The defect-rich characteristic nanostructure carbon favors the changing polarity and electron distribution in carbon matrix, thus facilitating an efficient adsorption of ions. Herein, a B,N,F-tridoped carbon material is successfully prepared on defect-rich sites by directly calcining two sodium salts, namely ethylenediaminetetraacetic acid tetrasodium salt (Na4EDTA) and ammonium tetrafluoroborate (NH4BF4). B refers to electron-donating atoms while F and N are electron-accepting atoms. The co-existence of electron-donating and electron-accepting atoms causes an asymmetrical spin and charge density, favoring palladium nanoparticles (Pd NPs) well dispersed on the carbon matrix. The heteroatoms efficiently control over the growth of Pd NPs and regulate the internal electron density. The catalytic performance is significantly enhanced with the obtained Pd/BNF-C catalyst for formic acid dehydrogenation, which has a lower activation barrier (36.4 kJ/mol) and a better reusability than those of free-heteroatom catalysts. The efficiency might be attributed to the strong interaction between Pd NPs and heteroatoms, and the electrons transfer from carbon material to Pd NPs, with benefits including the significant coupling effect of B,N,F-tridoping down to the atomic scale, abundant surface active defects, in-plane nanopore defects and more adjacent metal active sites.

Pt-based intermetallic compounds with tunable activity and selectivity toward hydrogen production from formic acid

Using first-principles methods, we studied formic acid dehydrogenation on the L11-type ordered Pt-based intermetallic compounds (i.e., X-Pt, X = Ag, Cu, Au, Pd, Ir, Rh, Tc, W, V). We found an adsorption-energy linear scaling relationship with positive slope between carbon monoxide (CO) and carboxyl (COOH) or hydrogen atom, but a weakly correlation with a negative slope for CO versus formate (HCOO) or CO versus hydroxyl (OH), which is attributed the beyond d-band-center model for the description of adsorption energies of HCOO and OH. And then, the selectivity of HCOOH dehydrogenation to HCOO (versus COOH) or COOH decomposition to CO2 (versus CO) on the Pt-based ordered alloys is regulated though breaking the adsorption-energy linear scaling relations of reaction intermediates. Our calculated results indicate that the L11-type CuPt is highly catalytic activity and selectivity toward formic acid decomposition and electrooxidation through the CO2 pathways of HCOOH→COOH+H→CO2+2H. This study underscores the importance of the unique adsorption-energy relations among reaction intermediates (e.g., CO versus OH) for screening high effective catalysts for hydrogen production of formic acid.

Reversible hydrogenation of carbon dioxide to formic acid using a Mn-pincer complex in the presence of lysine

Efficient hydrogen storage and release are essential for effective use of hydrogen as an energy carrier. In principle, formic acid could be used as a convenient hydrogen storage medium via reversible CO2 hydrogenation. However, noble metal-based catalysts are currently needed to facilitate the (de)hydrogenation, and the CO2 produced during hydrogen release is generally released, resulting in undesirable emissions. Here we report an α-amino acid-promoted system for reversible CO2 hydrogenation to formic acid using a Mn-pincer complex as a homogeneous catalyst. We observe good stability and reusability of the catalyst and lysine as the amino acid at high productivities (CO2 hydrogenation: total turnover number of 2,000,000; formic acid dehydrogenation: total turnover number of 600,000). Employing potassium lysinate, we achieve >80% H2 evolution efficiency and >99.9% CO2 retention in ten charge–discharge cycles, avoiding CO2 re-loading steps between each cycle. This process was scaled up by a factor of 18 without obvious drop of the productivity.

Defect-engineered MXene monolith enabling interfacial photothermal catalysis for high-yield solar hydrogen generation

Solar-driven formic acid dehydrogenation shows great potential for sustainable hydrogen utilization. Nevertheless, photothermal catalytic materials that are essential to dehydrogenation not only exhibit limited solar absorption and large heat loss but also heavily rely on noble metals, limiting efficient and low-cost hydrogen generation. Here, we report a porous MXene monolith that enables interfacial heat localization and propose a defect-engineering strategy for MXenes to realize the coordinated regulation of photothermal property and catalytic activity, which is further evidenced by density functional theory calculations. As a result, this design achieves a hydrogen generation rate of 401 mmol g −1 h −1 with an H 2 selectivity of 100% and catalytic stability over 45 h of operation, significantly surpassing many state-of-the-art, Pd-based noble metal materials. The work provides new insight into the design of photothermal catalytic MXenes and may open a new application toward solar hydrogen generation. • A defective MXene monolith enables both interfacial photothermal and catalysis • Defect engineering guides solar energy capture and intermediate conversion • A high hydrogen generation rate with long-term stability is presented Zhang and co-authors design a porous MXene monolith that enables interfacial heat localization and propose a defect-engineering strategy for MXenes to realize the coordinated regulation of photothermal and catalytic properties. The design may offer advantages over noble metals in solar fuel generation to concurrently realize high efficiency and cost effectiveness.

Selective dehydrogenation of aqueous formic acid over multifunctional γ-Mo2N catalysts at a temperature lower than 100 ℃

Efficient and selective dehydrogenation of aqueous formic acid (FA) for hydrogen production with non-noble-metal-based heterogeneous catalysts remains a great challenge. Herein, complete dehydrogenation of aqueous FA with a concentration as high as 40 vol% achieved a gas production rate of 293.9 mL/gcat./h by using a biomass-derived multifunctional γ-Mo2N catalyst synthesized with a facile pyrolysis process. No significant deactivation of catalysts was found during the 108 h-stability-test. Mechanism investigations indicate that the solvent H2O could occupy the Brønsted acid sites to prevent FA dehydration. The dehydrogenation activity was significantly improved by the cooperation of K-containing sites, N-doped sites, and the γ-Mo2N active sites, which could be responsible for the HCOO− intermediate generation and adsorption, H+ adsorption, and H-C bond cleavage of the adsorbed HCOO−, respectively. This study provided a novel strategy to improve the dehydrogenation performance of aqueous FA with non-noble-metal-based heterogeneous catalysts.