Electrocatalytic Activity Of Pd Research Articles

Enhanced Mass Activity and Stability of Bimetallic Pd‐Ni Nanoparticles on Boron‐Doped Diamond for Direct Ethanol Fuel Cell Applications

AbstractIn this work, electrochemical deposition of Pd and bimetallic Pd−Ni nanoparticles on an oxygen‐terminated boron‐doped diamond (BDD) substrate is described for use as an electrocatalyst in a direct ethanol fuel cell. A potentiostatic two‐step electrochemical method involving the electrodeposition of Ni nanoparticles on BDD followed by mono‐dispersed Pd nanoparticles was used for the fabrication of a Pd−Ni/BDD electrode. The electrocatalytic activity of the bimetallic Pd−Ni nanoparticles was evaluated in an alkaline solution containing ethanol and compared to that of the Pd nanoparticles alone. The bimetallic Pd−Ni nanoparticles showed 2.4 times higher mass activity than similar systems in the literature as well as stability when operated in alkaline media. The higher electrochemical response towards the electrooxidation of ethanol observed for the bimetallic electrocatalysts was attributed to the synergistic effects of the electron interaction at the interface of the two metals. Chronopotentiometric measurements revealed that Pd is more stable when anchored to the Ni nanoparticles. The optimised loading of mono‐dispersed Pd on a foreign Ni metal as nanoparticles plays a crucial role in achieving a high mass (3.63×106 mA/g) and specific (10.53 mA/cm2) electrocatalytic activity of Pd towards ethanol electrooxidation in alkaline media.

Electrochemically modified boron-doped diamond electrode with Pd and Pd-Sn nanoparticles for ethanol electrooxidation

The modification of hydrogen terminated boron-doped diamond (HBDD) electrode with pure palladium (Pd) and Pd-Sn (tin) nanoparticles is described in this study. For synthesis of Sn/HBDD and Pd-Sn/HBDD electrode, a potentiostatic two-step electrochemical method involving the electrodeposition of Sn followed by Pd was used, respectively. The modification of the HBDD electrode with Sn and noble metal Pd by forming bimetallic Pd-Sn nanoparticle leads to a higher electrocatalytic activity. The electrocatalytic activity of the bimetallic Pd-Sn nanoparticles was evaluated towards the electrooxidation of ethanol in alkaline media and compared with that of the Pd nanoparticles alone. The bimetallic Pd-Sn nanoparticles modified HBDD electrode exhibits higher current densities and less poisoning effects during ethanol electrooxidation compared to Pd/HBDD. The proper tuning of the Pd loading on a foreign metal along with the surface termination effects of the BDD electrode plays a crucial role in achieving a high mass (4.26×106mA/g) and specific (12.37mA/cm2) electrocatalytic activity of Pd towards ethanol electrooxidation. The aforementioned catalysts of this research possess a high poisoning resistance (If/Ib=1.63) and stability towards ethanol electrooxidation in alkaline media.

Selective Dehydrogenation of HCOOH on Zn-Decorated Pd(111) Surface Studied by First-Principles Calculations

Density functional calculation has been used to study the influences of atomic arrangements of Zn/Pd(111) bimetallic surface on the activity and selectivity of formic acid decomposition processes. A high catalytic selectivity for non-CO pathway of formic acid decomposition was found on Zn-rich Zn/Pd(111) surface with an isolated Pd trimer ensemble; and the O–H activation is the predominant process via the reaction of $${\text{HCOOH}} \to {\text{HCOO}} + {\text{H}},$$ while C–H activation is highly endothermic in the hydroxycarbonyl formation reaction via $${\text{HCOOH}}\to {\text{COOH}}+{\text{H}}$$ . Moreover, the high CO tolerance was found on the Zn-decorated Pd(111) surface with small Pd ensembles, and the desorption energy of CO is reduced to ~1.4 eV. These results indicate the electrocatalytic activity of Pd can be improved by incorporating the post transition metal of Zn through adjusting atomic composition and geometric distribution on surface. Graphical Abstract

Pd and PdCo alloy nanoparticles supported on polypropylenimine dendrimer-grafted graphene: A highly efficient anodic catalyst for direct formic acid fuel cells

For the first time, Pd and PdCo alloy nanoparticles supported on polypropylenimine dendrimer-grafted graphene (Pd and PdCo/PPI-g-G) are prepared and characterized with Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The electrocatalytic activity of Pd and PdCo/PPI-g-G are investigated in terms of formic acid electrooxidation in H2SO4 aqueous solution. The PdCo/PPI-g-G shows much higher formic acid oxidation activities in comparison with Pd/PPI-g-G, and it is more resistant to the surface poisoning. This improved electrocatalytic performance may be due to the fine dispersion of PdCo alloy nanoparticles and bi-functional effect. The kinetic parameters such as charge transfer coefficient and the diffusion coefficient of formic acid are estimated under the quasi steady-state conditions.

Study on Morphologies of Palladium Coated Foam Nickel Cathodes for Dechlorination of 2,4-Dichlorophenol

Electrolytically deposited palladium on polypyrrole film, which is electropolymerized using potentiostatic method, covered foam nickel electrode as a support was used as cathode for the electrocatalytic hydrodechlorination of 2, 4-dichlorophenol in aqueous solution. It is well known that the morphologies of polypyrrole films have dramatic influences on the dispersion of metals and the performance of the composite electrode. The influence of applied potential, temperature and polymerization time on the morphology of the films was studied by scanning electron microscopy (SEM). The fundamental electrocatalytic hydrodechlorination (ECH) results indicated that the electrocatalytic activity of Pd loaded polypyrrole foam nickel electrode is excellent for dechlorination of 2,4-dichlorophenol. The present study shows a promising choice of this kind of composite electrode for ECH.

Electrocatalytic Activity of Pd, Pt, and Rh for the Electro-oxidation of Ethanol in Alkaline Electrolyte: An Online DEMS Study

The electro-oxidation of ethanol was investigated on electrodeposited layers of Pd, Pt, and Rh in alkaline electrolyte. The reaction products were monitored by experiments of online differential electrochemical mass spectrometry (DEMS). Potentiodynamic curves for the ethanol electro-oxidation catalyzed by these three different metal electrocatalysts showed similar onset potentials, but the highest Faradaic current peak was observed for the Pt electrocatalyst. Online DEMS experiments evidenced similar amounts of CO2 for the three different materials, but Pd presented the higher production of ethylacetate (acetic acid). This indicated that the electrochemical oxidation of ethanol on the Pd surface occurred to a higher extent. The formation of methane, which was observed for Pt and Rh, after potential excursions to lower potentials, was absent for Pd. On the basis of the obtained results, it was stated that, on Pt and Rh, the formation of CO2 occurs mainly via oxidation of CO and CHx,ad species formed after dissociative adsorption of ethanol or ethoxy species that takes place only at low potentials. This indicates that the dissociative adsorption of ethanol or ethoxy species is inhibited at higher potentials on Pt and Rh. On the other hand, on the Pd electrocatalyst, the reaction may occur via nondissociative adsorption of ethanol or ethoxy species at lower potentials, followed by oxidation to acetaldehyde and, after that, by a further oxidation step to acetic acid on the electrocatalyst surface. Additionally, in a parallel route, the acetaldehyde molecules adsorbed on the Pd surface can be deprotonated, yielding a reaction intermediate in which the carbon–carbon bond is less protected, and therefore, it can be dissociated on the Pd surface, producing CO2, after potential excursions to higher potentials.

Reduced graphene oxide supported palladium–silver bimetallic nanoparticles for ethanol electro-oxidation in alkaline media

Palladium–silver bimetallic nanoparticles loaded on reduced graphene oxide (Pd–Ag/RGO) were prepared by co-reduction of mixed metal salts and graphene oxide (GO) with urea-assisted ethylene glycol (EG). The as-obtained Pd–Ag/RGO nanocomposites were characterized by X-ray diffraction, transmission electronic microscopy, and UV–Vis absorption spectroscopy. The results show that the nanoparticles with an average particle size of 5 nm are dispersed on the surface of RGO highly uniformly, besides the Pd–Ag bimetallic nanoparticles are more helpful to promote the reduction of GO than monometal ones. The electrochemical activities of the as-prepared nanocomposites for ethanol oxidation were investigated by using cyclic voltammetry and chronoamperometry in alkaline solution. Compared to the Pd–Ag/E-tek carbon (Pd–Ag/C) and Pd–Ag/multi-walled carbon nanotubes (Pd–Ag/MWCNTs) which were fabricated by the same method, the Pd–Ag/RGO exhibit much higher electrocatalytic activity, stronger tolerance to CO and better stability during the ethanol electro-oxidation reaction in alkaline media. The electrocatalytic performances of Pd–Ag/RGO with different mass ratios of Pd–Ag toward ethanol oxidation in alkaline media were also studied. The results indicate that the electrocatalytic activity of Pd–Ag/RGO with 1:1 mass ratio of Pd–Ag is the best.

Preparation of palladium nanoparticles–titanium electrodes as a new anode for direct methanol fuel cells

Pd nanoparticle/Ti electrodes are prepared by electroless plating of palladium on titanium plates. The morphology and surface analysis of Pd nanoparticle/Ti electrodes are investigated using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The results indicate that palladium nanoparticles are homogeneously deposited on the surface of titanium plates. The electro-catalytic activity of Pd nanoparticle/Ti electrodes in the methanol electro-oxidation is studied by cyclic voltammetry and chronoamperometry methods. The results show that the electro-catalytic oxidation of methanol on the Pd nanoparticle/Ti electrode improved compare to pure palladium electrode and confirmed the better electro-catalytic activity and stability of these new electrodes.

Development of Pd and Pd–Co catalysts supported on multi-walled carbon nanotubes for formic acid oxidation

Pd–Co and Pd catalysts were prepared by the impregnation synthesis method at low temperature on multi-walled carbon nanotubes (MWCNTs). The nanotubes were synthesized by spray pyrolysis technique. Both catalysts were obtained with high homogeneous distribution and particle size around 4 nm. The morphology, composition and electrocatalytic properties were investigated by transmission electron microscopy, scanning electron microscopy–energy dispersive X-ray analysis, X-ray diffraction and electrochemical measurements, respectively. The electrocatalytic activity of Pd and PdCo/MWCNTs catalysts was investigated in terms of formic acid electrooxidation at low concentration in H 2SO 4 aqueous solution. The results obtained from voltamperometric studies showed that the current density achieved with the PdCo/MWCNTs catalyst is 3 times higher than that reached with the Pd/MWCNTs catalyst. The onset potential for formic acid electrooxidation on PdCo/MWCNTs electrocatalyst showed a negative shift ca. 50 mV compared with Pd/MWCNTs.

Electrocatalytic Activity of Pd−Co Bimetallic Mixtures for Formic Acid Oxidation Studied by Scanning Electrochemical Microscopy

The electrochemical oxidation of formic acid was studied by the tip generation-substrate collection (TG-SC) mode of scanning electrochemical microscopy (SECM), extending the number of applications of SECM in electrocatalysis. Formic acid was generated at a Hg on Au ultramicroelectrode (UME) tip by reduction of CO(2) in a 0.1 M KHCO(3) solution saturated with this gas. The electrocatalytic activity of different Pd-Co bimetallic compositions was evaluated using a Pd-Co electrocatalyst array formed by spots deposited onto glassy carbon (GC) as a SECM substrate. The SECM tip, which generated a constant formic acid flux, was scanned above the array and the oxidation current generated when formic acid was collected by active electrocatalytic spots was displayed as a function of tip position. This generated a SECM image that showed the electrocatalytic activity of each spot. SECM screening identified Pd(50)Co(50) (Pd/Co = 50:50, atomic ratio) as a better electrocatalyst toward the formic acid oxidation than pure Pd or Pt in 0.1 M KHCO(3) solution and this result was confirmed by cyclic voltammetry. Positive feedback was observed for the most active compositions of Pd-Co which suggests fast reaction kinetics and chemical reversibility during the oxidation of formic acid to CO(2). Moreover this feedback increases the contrast between active and non-active spots in this imaging mode.

Rapid Screening of Bimetallic Electrocatalysts for Oxygen Reduction in Acidic Media by Scanning Electrochemical Microscopy

Additional bimetallic electrocatalysts for the oxygen reduction reaction (ORR) in acidic media were designed using a previously reported thermodynamic selection guide. The electrocatalyst mixtures were prepared in large arrays on glassy carbon substrates and the electrocatalytic activity was screened using scanning electrochemical microscopy (SECM). Activities were measured for a range of bimetallic combinations that showed a synergetic electrocatalytic effect during screening, including Au–V, Ag–V, Pd–Mn, and Pd–V. Upon initial screening, a highly active electrocatalytic combination consisting of 60:40 Pd–V was identified. Using rotating disk electrode (RDE) experiments, the high activity of this combination for the ORR in acidic media was confirmed when the electrocatalysts were supported on Vulcan carbon. The electrocatalytic activity of Pd–V was close to that exhibited by Pt, the electrocatalyst of choice for the ORR in acidic media, and thus is another example of a nonplatinum catalyst with high activity that follows the previous strategy for catalyst design.

Teaching Chest Disease: The Coin Lesion

The modification of hydrogen terminated boron-doped diamond (HBDD) electrode with pure palladium (Pd) and Pd-Sn (tin) nanoparticles is described in this study. For synthesis of Sn/HBDD and Pd-Sn/HBDD electrode, a potentiostatic two-step electrochemical method involving the electrodeposition of Sn followed by Pd was used, respectively. The modification of the HBDD electrode with Sn and noble metal Pd by forming bimetallic Pd-Sn nanoparticle leads to a higher electrocatalytic activity. The electrocatalytic activity of the bimetallic Pd-Sn nanoparticles was evaluated towards the electrooxidation of ethanol in alkaline media and compared with that of the Pd nanoparticles alone. The bimetallic Pd-Sn nanoparticles modified HBDD electrode exhibits higher current densities and less poisoning effects during ethanol electrooxidation compared to Pd/HBDD. The proper tuning of the Pd loading on a foreign metal along with the surface termination effects of the BDD electrode plays a crucial role in achieving a high mass (4.26 × 106 mA/g) and specific (12.37 mA/cm2) electrocatalytic activity of Pd towards ethanol electrooxidation. The aforementioned catalysts of this research possess a high poisoning resistance (If/Ib = 1.63) and stability towards ethanol electrooxidation in alkaline media.