Activity For Formic Acid Oxidation Research Articles

Formic acid oxidation at palladium nanoparticles supported on polyaniline modified carbon fibre paper

Preformed palladium nanoparticles (PdNP) have been drop-coated onto polyaniline (PANI)-modified carbon fibre paper to prepare extended reaction zone anodes for formic acid oxidation that take advantage of the promoting effect of polyaniline. The influence of the PANI preparation conditions on the activity of the PdNP was investigated. It was found that PANI deposited under galvanostatic and potentiostatic conditions produced similar enhancements in activity for formic acid oxidation, while PANI produced by potential cycling (PD-PANI) had a much smaller effect. This difference is attributed to the much later onset of the oxidation of the PD-PANI layer. The results are compared with those for electrodes with spontaneously deposited Pd (reduction of PdCl2 by the PANI layer) and a commercial carbon supported catalyst. The preformed PdNP on PANI provided the highest activities per Pd surface area. However, transport losses were much larger than at planer electrodes prepared similarly.

Highly active carbon supported palladium catalysts decorated by a trace amount of platinum by an in-situ galvanic displacement reaction for formic acid oxidation

Aimed at reducing platinum usage and improved catalytic activity for formic acid oxidation, a series of Pt decorated Pd/C catalysts are prepared by an in-situ galvanic displacement reaction between freshly prepared Pd/C ink and H2PtCl6 in an aqueous solution. The catalysts with 4 nm particle sizes and 20 wt.% loadings have been characterized by transmission electron microscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy (XPS). The electrochemical evaluations by cyclic voltammetry are conducted to test out the CO tolerance and catalytic activities. In addition to XPS analysis, a theoretical calculation has been attempted the first time to find out the surface Pd/Pt molar ratios. The decay rate of the catalysts has been evaluated by the percentage of the forward/backward peak current retained using the value at the 20th cycle divided by that in the first cycle. Compared with a Pd/C benchmark, all Pt decorated Pd/C register enhanced activity while the cost remains virtually unchanged. The optimized catalyst is found to have a Pd/Pt molar ratio of 75:1 but with 2.5 times activity relative to that of Pd/C.

Photoelectrochemical enhancement of ternary nanocomposite electrode polyoxometalate/copper quantum dots/TiO2 with electrocatalytic performance of formic acid oxidation

In this work, we fabricate a ternary nanocomposite photoelectrode consisting of TiO2 nanoparticles, polyoxometalate (P2W18) and copper quantum dots (Cu QDs) so as to create a synergistic effect of the ternary nanocomposite on photovoltaic and photoelectrocatalytic performances. Both the high electron mobility from low cost Cu QDs and the high electro-hole separation efficiency from P2W18 could evidently improve the photoelectrochemical performance of TiO2. Transient photocurrent and current-voltage curves measurements demonstrate that both the photocurrent response and power conversion efficiency of the P2W18/Cu/TiO2 film were markedly enhanced in comparison with that of the only TiO2 film and the P2W18/TiO2 film, respectively. Furthermore, the photoelectrode also exhibited significant photoelectrocatalytic activity for formic acid oxidation. The substitute of copper quantum dots for noble metals in electrode is a favorable innovation for the practical application of photoelectrochemical devices.

CN x -modified montmorillonite as support to immobilize Pd and its enhanced electrocatalytic activity for formic acid oxidation

Nature clay, i.e., montmorillonite (MMT), can be used as support materials of anode electrocatalyst in the direct formic acid fuel cell. The nitrogen-containing composite support (MMT-CN x ) was prepared via carbonizing MMT which was covered by polyaniline. Pd/MMT-CN x and Pd/C catalysts were prepared as formic acid oxidation catalysts using an improved liquid reduction method. The composite, structure, surface properties, and electrical conductivity of the supports and catalysts were studied by energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS). The results showed that well-dispersed Pd nanoparticles with a narrow size distribution of 3.5–5.5 nm could be easily prepared on the MMT-CN x . Larger electrochemical specific area (ECSA) was obtained for Pd/MMT-CN x than Pd/C according to CO-stripping voltammetry. Cyclic voltammetry (CV) and chronoamperometry (CA) measurements showed better catalytic activity and stability of the Pd/MMT-CN x catalyst than the conventional Pd/C catalyst for formic acid electrooxidation. Larger ECSA and doped nitrogen in the support of the Pd/MMT-CN x catalyst may be the main reason of higher activity and better stability for formic acid oxidation compared with the Pd/C catalyst. The results offered potential application of composite support (MMT-CN x ) for the catalyst of the direct formic acid fuel cell.

Pd@Pt/C catalysts fabricated using chemisorbed CO as in situ reductant: advanced catalytic behaviour for formic acid oxidation

A Pd sub-layer on a Pt substrate is fabricated stoichiometrically using chemisorbed CO as an in situ reductant. The Pd sub-layer of the Pd@Pt/C catalysts exhibits a more negative oxidation peak and 3 times higher mass activity for formic acid oxidation than commercial Pd/C.

Palladium Nanodendrites Deposited on Electrochemically Activated Carbon Based Support for Electrocatalytic Applications

This paper focuses on the morphological nature of Pd electrodeposited on different carbon supports such as Vulcan XC-72R (VCX), carbon nanotubes (CNTs) and wood apple shell carbon (WASC), and presents a comparative assessment of the catalytic activity on different supports towards formic acid (HCOOH) oxidation and oxygen reduction reaction (ORR) in low-temperature fuel cells. The carbon supports subjected to an electrochemical activation by potential cycling in an acidic media followed by deposition of Pd showed dendrite formation as confirmed by scanning electron micrographs irrespective of the morphology of carbon material. Pd dendrites on WASC showed the highest electrochemical surface area of 86.1 m2g-1 among the electrocatalysts studied. The carbon supported Pd dendrite showed the following order towards the activity of formic acid oxidation: WASC > VXC > CNTs, whereas for oxygen reduction reaction the activity was in the order CNTs > WASC > VXC. The results suggest the need for different carbon support for anode and cathode reaction of direct liquid fuel cells.

Pd–Cu Bimetallic Tripods: A Mechanistic Understanding of the Synthesis and Their Enhanced Electrocatalytic Activity for Formic Acid Oxidation

This article reports a facile synthesis of Pd‐Cu bimetallic tripods with a purity over 90%. Two requirements must be met in order to form tripods: i) formation of triangular, plate‐like seeds during the nucleation step and ii) preferential deposition of atoms onto the three corners of a seed during the growth step. In this synthesis, these requirements are fulfilled by adding CuCl2 and KBr into an aqueous synthesis. Specifically, it is demonstrated that the Cu atoms resulting from underpotential deposition could greatly reduce the energy barrier involved in the formation of triangular seeds with planar defects because of the much lower stacking fault energy (41 mJ·m−2 for Cu vs 220 mJ·m−2 for Pd). The Br− ions could strongly bind to the three {100} side faces of a triangular seed, forcing the Pd atoms to grow from the three corners of a seed to generate a tripod. When compared with commercial Pd black, the Pd‐Cu tripods exhibited substantially enhanced catalytic activity toward the electro‐oxidation of formic acid. This work offers a general strategy for the synthesis of nanocrystals with a tripod structure for catalytic applications.

Effect of Au and Ru in Au@Pd and Ru@Pd Core@Shell Nanoparticles for Direct Formic Acid Fuel Cells

In this research, the effect of Au and Ru in Au@Pd and Ru@Pd on the electronic perturbation and the formic acid oxidation activity is investigated. Au@Pd/C and Ru@Pd/C core@shell nanoparticles with 2 nm Pd shell are synthesized via a two-step process. The electronic perturbation and electrochemical activity of the nanoparticles are tested through X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) measurements, respectively. A positive 0.15 eV binding energy shift for Pd 3p3/2 relative to that of Pd/C is observed for Au@Pd/C nanoparticles suggesting that there is charge transfer from Pd to Au. In addition, CV results show that the peak current density of Au@Pd/C, Ru@Pd/C, and Pd/C are 2.1 mA/cm2, 1.5 mA/cm2, and 1.2 mA/cm2, respectively. Thus, Au@Pd/C presents the highest activity towards FAO, indicating that a charge transfer from Pd to Au leads to formic acid oxidation activity enhancement.

Controllable Modification of the Electronic Structure of Carbon-Supported Core–Shell Cu@Pd Catalysts for Formic Acid Oxidation

This study analyzes the synthesis of carbon-supported core–shell structured Cu@Pd catalysts (Cu@Pd/C) through a galvanic replacement reaction to be utilized in the electrocatalytic oxidation of formic acid. The strategy used in this study explores the relationship among lattice strain, electronic structure, and catalytic performance. X-ray diffraction and X-ray photoelectron spectroscopy indicate that the inclusion of Cu in the nanocatalyst increases lattice strain and results in a downshift of the d-band of palladium. Electrochemical tests show that Cu@Pd/C catalysts exhibit weaker adsorption strength for CO with increased Cu content, which can be attributed to the downshift of the electronic d-band. For the synthesized materials, the Cu@Pd/C catalyst with a Cu:Pd atomic ratio of 27:73 is found to have the highest activity for formic acid oxidation. A peaklike plot between activity and atomic composition is acquired and reveals the relationship among lattice strain, electronic structure, and catalytic pe...

Novel palladium flower-like nanostructured networks for electrocatalytic oxidation of formic acid

Novel Pd flower-like nanostructured networks are synthesized via a simple CO-assisted reduction. The morphology and size of the Pd nanostructures are found to strongly depend on the temperature and solvent during the synthesis process. Such Pd flower-like nanostructured networks exhibit a much enhanced activity of about 3 times of that on conventional Pd nanoparticles towards the electrocatalytic oxidation of formic acid. The specific activity of formic acid oxidation on Pd nanostructures is also greatly improved, indicating that the formation of flower-like nanostructured networks is beneficial for the electrooxidation of formic acid. Thus, it could be served as highly active catalyst for formic acid electrooxidation although the stability needs to be greatly improved.

Bimetallic alloy Pt/Ag nanoparticles with enhanced catalytic activity for formic acid oxidation

Here, we report the synthesis of Pt/Ag bimetallic alloy catalyst through combining the ion implantation and electrodeposition method. Ag nanoparticles are employed as the seeds for the growth of Pt nanoparticles. Pt/Ag alloy catalyst demonstrates much higher catalytic activity than pure Pt catalyst, which is about three times more active on the basis of equivalent Pt electrochemically active surface area than that of the pure Pt catalyst. The ion implantation of Ag efficiently enhances the catalytic activity of Pt catalyst for formic acid oxidation.

Density Functional Theory Studies of Formic Acid Oxidation on Pd (111), (100) and (110) Facet

In the last fifty years, great interest and investment have been devoted to direct formic acid fuel cells (DFAFC) for its high-energy conversion efficiency, low operating temperature, low pollutant emission, ease of handling and processing of the liquid fuels, and integrated well with the existing energy infrastructure[1-3]. The electro-oxidation of formic acid in DFAFC is currently being investigated by many research groups.Pd is the one of the most promising anode catalysts used in DFAFC due to its higher formic acid oxidation activity and excellent CO tolerance[4]. However, the study of structure sensitivity of formic acid oxidation on Pd (111), (100) and (110) facet is rare. So weather the dsorption behaviors and oxidation mechanisms of formic acid on different Pd facets are the same.In the present study, we calculated the adsorption and decompostion of formic acid on the Pd (111), (100) and (110) Facet. The results show that Pd (100) is the best facet for the dissociation of formic acid, which means the (100) facet exhibit the highest activity toward the formic acid electrooxidation.Reference[1] Chen, X. et al., J. Am. Chem. Soc., 133(11), 3693 (2011).[2] Maiyalagan, T. et al., J. Power Sources, 211, 147 (2012)[3] Mazumder, V. et al., Nano Lett., 12(2), 1102 (2012)[4] Yang, J. et al., J. of Mater. Chem., 21(10), 3384 (2011)

Preparation of Carbon Nanotubes Supported Pd-Au Catalyst and Their Electrocatalytic Activity for Formic Acid Oxidation

Naphthalen-1-ylmethylphosphonic acid was modified on multiwall carbon nanotube( MWCNT) by the π-π stacking interaction. Then,the Pd catalyst was supported on it. Furthermore,the MWCNT supported Pd-Au( Pd-Au/MWCNT) catalyst was facially prepared by the replacement reaction between Pd nanoparticles and HAuCl 4. Transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy measurements showed that non-alloyed Pd-Au nanoparticles were highly dispersed on the surface of MWCNT. Cyclic voltammetry and chronoamperometric measurements indicated that the Pd-Au/MWCNT catalyst exhibited better electrocatalytic activity and stability for formic acid oxidation than that of the Pd/MWCNT catalyst.

Preparation and characterizations of highly dispersed carbon supported PdxPty/C catalysts by a modified citrate reduction method for formic acid electrooxidation

Carbon supported PdxPty/C (atomic ratio x:y from 1:1 to 6:1) have been prepared by a modified citrate reduction method assisted by inorganic stabilizers. Without using high molecular capping agents as stabilizers, the PdxPty/C catalysts are highly dispersed on the carbon support and no particle aggregations are found for the PdxPty/C catalysts. X-ray photoelectron spectroscopy reveals either Pt or Pd segregation for the PdxPty/C catalysts depending on Pd/Pt atomic ratio. CO stripping in 0.5 M H2SO4 and repeated formic acid oxidation cyclic voltammetry in 0.5 M HCHO + 0.5 M H2SO4 have been conducted to test out the CO tolerance and stability of the catalysts, respectively. It has been found that, with the increase of Pd/Pt atomic ratio, the CO stripping peak potential increases (less CO tolerant), whereas the catalyst stability towards formic acid oxidation decreases. The as-prepared catalysts reveal excellent mass-normalized formic acid oxidation activity as compared with published results possibly due to high dispersion and the absence of high molecular capping agents.

One-pot synthesis of Pd–Pt@Pd core–shell nanocrystals with enhanced electrocatalytic activity for formic acid oxidation

Pd–Pt@Pd core–shell nanocrystals were directly synthesized through an aqueous solution approach without any preformed Pd or Pt seeds.

Formic Acid Oxidation at Platinum-Bismuth Clusters

Formic acid oxidation was studied on platinum-bismuth deposits on glassy carbon (GC) substrate. The catalysts of equimolar ratio were prepared by potentiostatic deposition using chronocoulometry. Bimetallic structures obtained by two-step process, comprising deposition of Bi followed by deposition of Pt, were characterized by AFM spectroscopy which indicated that Pt crystallizes preferentially onto previously formed Bi particles. The issue of Bi leaching (dissolution) from PtBi catalysts, and their catalytic effect alongside the HCOOH oxidation is rather unresolved. In order to control Bi dissolution, deposits were subjected to electrochemical oxidation, in the relevant potential range and supporting electrolyte, prior to use as catalysts for HCOOH oxidation. Anodic striping charges indicated that along oxidation procedure most of deposited Bi was oxidized. ICP mass spectroscopy analysis of the electrolyte after this electrochemical treatment revealed that Bi was only partly dissolved indicating the possibility for formation of some Bi oxide species. Moreover, EDX analysis of the as prepared (Pt@Bi/GC) catalysts and those oxidized confirmed appreciably higher content of oxygen in the latter. Catalysts prepared in this way exhibit about 10 times higher activity for formic acid oxidation in comparison to pure Pt, as revealed both by potentiodynamic and quasy-potentiostatic measurements. This high activity is the result of well-balanced ensemble effect induced by Bi-oxide species interrupting Pt domains. Prolonged cycling and chronoamperometry tests disclosed exceptional stability of the catalyst during formic acid oxidation. The activity is compatible with the activity of previously studied Pt2Bi alloy but the stability is significantly better.

Nanoporous PdPt alloy as a highly active electrocatalyst for formic acid oxidation

Nanoporous (NP) PdPt alloy with uniform ligament size and controllable bimetallic ratio is easily fabricated through the selective dealloying of Al from PdPtAl ternary alloys. Compared with commercial Pd/C, Pt/C, NP-Pd, and NP-Pt catalysts, the as-prepared NP-PdPt exhibits greatly enhanced electrocatalytic activity for formic acid oxidation. Moreover, NP-PdPt presents superior catalytic durability upon alloying with Pt, with less loss of the formic acid oxidation activity upon long term potential scans. The NP-PdPt alloy holds great potential in applications as a promising anode catalyst in direct formic acid fuel cells.

Highly active Pd and Pd–Au nanoparticles supported on functionalized graphene nanoplatelets for enhanced formic acid oxidation

Pd and Pd–Au nanoparticles supported on poly(diallyldimethylammonium chloride) (PDDA) functionalized graphene nanoplatelets (GNP) have been synthesized by the ethylene glycol reduction method and characterized by transmission electron microscopy (TEM) and electrochemical measurements for formic acid oxidation. TEM analysis shows that the Pd–Au nanoparticles are uniformly distributed on the surface of graphene nanoplatelets with an average particle size of 6.8 nm. The Pd–Au nanoparticles supported on PDDA–xGNP show higher activity for formic acid electro-oxidation than Pd nanoparticles supported on PDDA–xGNP and Pd or Pd–Au supported on traditional Vulcan XC-72 carbon. The higher catalytic activity of Pd–Au/PDDA–xGNP is mainly due to the alloying of Pd with Au. The promotional effect of Au and the absence of continuous Pd sites significantly suppress the poisoning effects of CO, enhancing the catalytic activity for formic acid oxidation and making them promising for direct formic acid fuel cells (DFAFC).

Size-controlled synthesis of mesoporous palladium nanoparticles as highly active and stable electrocatalysts.

We report a solution phase synthesis of monodispersed mesoporous Pd nanoparticles (MPNs) with narrow particle size distributions. The average particle sizes can be controlled to a range of 25 nm to 42 nm, by utilizing cationic surfactants (as structure-directing agents) and triblock copolymers (as protective agents for controlled Pd deposition). The obtained MPNs exhibit very high electrocatalytic activity in formic acid oxidation.

Multi-generation overgrowth induced synthesis of three-dimensional highly branched palladium tetrapods and their electrocatalytic activity for formic acid oxidation

Highly branched noble metal nanostructures are highly attractive for catalytic applications owing to their specific physical and chemical properties. In this work, three-dimensional highly branched palladium tetrapods (Pd-THBTs) have been constructed in the presence of polyvinylpyrrolidone (PVP) through one-step hydrothermal reduction of ethylenediamine-tetramethylene phosphonate-palladium(II) (EDTMP-Pd(II)) by formaldehyde. The morphology and structure of the Pd-THBTs were fully characterized and the growth mechanism was explored and discussed based on the experimental observation. The concave Pd tetrahedra grew into highly branched Pd tetrapods consisting of four nanothorn-like branches with tetrahedral dimensions through interesting multi-generation nanocrystal overgrowth. The electrocatalytic activities of the as-synthesized Pd-THBTs toward formic acid oxidation were also studied by cyclic voltammetry and chronoamperometry. The Pd-THBTs showed higher catalytic activity and stability for formic acid oxidation than the commercial Pd black.