Decomposition of formic acid over silica encapsulated and amine functionalised gold nanoparticles

Second Sphere Effects Promote Formic Acid Dehydrogenation by a Single-Atom Gold Catalyst Supported on Amino-Substituted Graphdiyne

Regulating the second sphere of homogeneous molecular catalysts is a common and effective method to boost their catalytic activities, while the second sphere effects have rarely been investigated for heterogeneous single-atom catalysts primarily due to the synthetic challenge for installing functional groups in their second spheres. Benefiting from the well-defined and readily tailorable structure of graphdiyne (GDY), an Au single-atom catalyst on amino-substituted GDY is constructed, where the amino group is located in the second sphere of the Au center. The Au atoms on amino-decorated GDY displayed superior activity for formic acid dehydrogenation compared with those on unfunctionalized GDY. The experimental studies, particularly the proton inventory studies, and theoretical calculations revealed that the amino groups adjacent to an Au atom could serve as proton relays and thus facilitate the protonation of an intermediate Au-H to generate H₂ . Our study paves the way to precisely constructing the functional second sphere on single-atom catalysts.

Interference effects of oxyanions commonly found in natural waters on the catalytic reduction of nitrate in water

In this work, the influence of oxyanions on the catalytic reduction of nitrates using formic acid as the reducing agent was studied as well as the influence of bicarbonate, sulfate, and phosphate co-anions on the catalytic nitrate reduction with Pd:In/Al₂O₃ (1:0.25 wt.%). A negative effect on nitrate conversion was observed in the following order: phosphate > sulfate > bicarbonate, showing a strong influence of electrostatic adsorption on the catalytic reduction of nitrate. However, no direct trend was observed relating the levels of interferents to the impact on the selectivity of the bimetallic catalyst using formic acid as a reducing agent. For both bicarbonate and phosphate, at lower levels, higher selectivity to nitrogen was obtained than for the reaction in the absence of interferents. On the other hand, increasing sulfate concentration led to a decrease in nitrate conversion. The mixtures of co-anions also showed a decrease in the catalytic activity. At 120 min, a N₂ selectivity higher than 95% was obtained, except for the C50-S20 (bicarbonate 50 ppm-sulfate 20 ppm) mixture which showed the lowest selectivity to N₂ value (87.3%). The loss of catalyst activity was found to be reversible and not permanent.

New bidental sulfur-doped graphene quantum dots modified with gold as a catalyst for hydrogen generation

Disadvantages of fossil fuels encourage researchers to develop clean combustion sources, in particular, H₂ due to the high potential energy and safe by-products. Herein, Au was deposited on S-doped graphene quantum dots to obtain a heterogeneous photocatalyst for the degradation of formic acid toward H₂ generation. Insertion of thiol groups on graphene quantum dots was carried out by self-condensation reaction of citric acid in the presence of Dimaval, as the thiol groups carrier. After the complexation of Au with the prepared S-doped graphene quantum dots, the catalytic activity of composite was evaluated in formic acid degradation to generate H₂ under visible light. Au@S-doped graphene quantum dots demonstrated superior catalytic activity with the turnover frequency up to 112 h^-1. The reaction enjoys significant benefits such as stability and recyclability of the catalyst, excellent reaction rate, and mild reaction conditions.

Decomposition of Additive-Free Formic Acid Using a Pd/C Catalyst in Flow: Experimental and CFD Modelling Studies

The use of hydrogen as a renewable fuel has gained increasing attention in recent years due to its abundance and efficiency. The decomposition of formic acid for hydrogen production under mild conditions of 30 °C has been investigated using a 5 wt.% Pd/C catalyst and a fixed bed microreactor. Furthermore, a comprehensive heterogeneous computational fluid dynamic (CFD) model has been developed to validate the experimental data. The results showed a very good agreement between the CFD studies and experimental work. Catalyst reusability studies have shown that after 10 reactivation processes, the activity of the catalyst can be restored to offer the same level of activity as the fresh sample of the catalyst. The CFD model was able to simulate the catalyst deactivation based on the production of the poisoning species CO, and a sound validation was obtained with the experimental data. Further studies demonstrated that the conversion of formic acid enhances with increasing temperature and decreasing liquid flow rate. Moreover, the CFD model established that the reaction system was devoid of any internal and external mass transfer limitations. The model developed can be used to successfully predict the decomposition of formic acid in microreactors for potential fuel cell applications.

Effects of rare earth metal doping on Au/ReZrO2 catalysts for efficient hydrogen generation from formic acid

Rare earth metal doped ZrO₂ can promote the formation of oxygen vacancies in zirconia, which enhances the metal–support interaction, finally promoting catalytic activity of FA dehydrogenation.

Role of the Support in Gold-Containing Nanoparticles as Heterogeneous Catalysts

In this review, we discuss selected examples from recent literature on the role of the support on directing the nanostructures of Au-based monometallic and bimetallic nanoparticles. The role of support is then discussed in relation to the catalytic properties of Au-based monometallic and bimetallic nanoparticles using different gas phase and liquid phase reactions. The reactions discussed include CO oxidation, aerobic oxidation of monohydric and polyhydric alcohols, selective hydrogenation of alkynes, hydrogenation of nitroaromatics, CO₂ hydrogenation, C–C coupling, and methane oxidation. Only studies where the role of support has been explicitly studied in detail have been selected for discussion. However, the role of support is also examined using examples of reactions involving unsupported metal nanoparticles (i.e., colloidal nanoparticles). It is clear that the support functionality can play a crucial role in tuning the catalytic activity that is observed and that advanced theory and characterization add greatly to our understanding of these fascinating catalysts.

Selective formic acid dehydrogenation at low temperature over a RuO2/COF pre-catalyst synthesized on the gram scale

Selective formic acid dehydrogenation over an efficient RuO₂/COF pre-catalyst with good dispersion of the active metal and large N-content on the COF support.

Ultrafine PdAu nanoparticles immobilized on amine functionalized carbon black toward fast dehydrogenation of formic acid at room temperature

Ultrafine and highly dispersed PdAu nanoparticles were immobilized on amine functionalized carbon black (VXC-72-NH₂) for dehydrogenation of formic acid (FA). The introduction of amines is of vital importance for the formation of ultrafine PdAu nanoparticles (∼1.5 nm). Moreover, the presence of the amino groups also increased the electron density of PdAu nanoparticles, and this effect facilitated the formation of metal-formate, which further enhanced the rate of the catalytic dehydrogenation of FA. The as-prepared Pd_0.6Au_0.4/VXC-72-NH₂ exhibited high catalytic activity and 100% H₂ selectivity for dehydrogenation of formic acid without any additive, with turnover frequency (TOF) values of 7385 h^-1 at 298 K and 17 724 h^-1 at 333 K, which are the highest TOF values ever reported among heterogeneous catalysts for FA dehydrogenation.

On the nature of active sites for formic acid decomposition on gold catalysts

Atomic scale size-sensitivity of the catalytic properties of sub-nanometer gold clusters for HCOOH decomposition.

Thermoresponsive Amphiphilic Block Copolymer-Stablilized Gold Nanoparticles: Synthesis and High Catalytic Properties

A series of novel well-defined 8-hydroxyquinoline (HQ)-containing thermoresponsive amphiphilic diblock copolymers {poly(styrene- co-5-(2-methacryloylethyloxy-methyl)-8-quinolinol)- b-poly( N-isopropylacrylamide) P(St- co-MQ)- b-PNIPAm (P1,2), P(NIPAm- co-MQ)- b-PSt (P3,4)} and triblock copolymer poly( N-isopropylacrylamide)- b-poly(methyl-methacrylate- co-5-(2-methacryloylethyloxymethyl)-8-quinolinol)- b-polystyrene PNIPAm- b-P(MMA- co-MQ)- b-PSt (P5) were prepared by reversible addition-fragmentation chain-transfer (RAFT) polymerization, and their self-assembly behaviors were studied. Block copolymer P1-P5-stabilized gold nanoparticles (Au@P1-Au@P5) with a small size and a narrow distribution were obtained through the in situ reduction of gold precursors in an aqueous solution of polymer micelles with HQ as the coordination groups. The resulting Au@P nanohybrids possessed excellent catalytic activity for the reduction of nitrophenols using NaBH₄. The size, morphology, and surface chemistry of Au NPs could be controlled by adjusting the structure of block polymers with HQ in different block positions, which plays an important role in the catalytic properties. It was found that longer chain lengths of hydrophilic or hydrophobic segments of block copolymers were beneficial to elevating the catalytic activity of Au NPs for the reduction of nitrophenols, and the spherical nanoparticles (Au@P5) stabilized with triblock copolymers exhibit higher catalytic performance. Surprisingly, the gold nanowires (Au@P4) produced with P4 have the highest catalytic activity due to a large abundance of grain boundaries. Excellent thermoresponsive behavior for catalytic reaction makes the as-prepared Au@P hybrids an environmentally responsive nanocatalytic material.

Hydrolytic dehydrogenation of ammonia borane over ZIF-67 derived Co nanoparticle catalysts

In this work, we exploited zeolitic imidazolate framework ZIF-67 as a sacrificial precursor to prepare Co nanoparticles supported on nanoporous nitrogen-doped carbon.

PdAu bimetallic nanoparticles anchored on amine-modified mesoporous ZrSBA-15 for dehydrogenation of formic acid under ambient conditions

Highly active catalysts for the dehydrogenation of formic acid were screened by using different amine-modified ZrSBA-15 as supports.