Electrochemical Deposition Of Palladium Research Articles

Simultaneous Sulfite Electrolysis and Hydrogen Production Using Ni Foam-Based Three-Dimensional Electrodes.

The electrochemical oxidation of sulfite ions offers encouraging advantages for large-scale hydrogen production, while sulfur dioxide emissions can be effectively used to obtain value-added byproducts. Herein, the performance and stability during sulfite electrolysis under alkaline conditions are evaluated. Nickel foam (NF) substrates were functionalized as the anode and cathode through electrochemical deposition of palladium and chemical oxidation to carry out the sulfite electro-oxidation and hydrogen evolution reactions, respectively. A combined analytical approach in which a robust electrochemical flow cell was coupled to different in situ and ex situ measurements was successfully implemented to monitor the activity and stability during electrolysis. Overall, satisfactory sulfite conversion and hydrogen production efficiencies (>90%) at 10 mA·cm-2 were mainly attributed to the use of NF in three-dimensional electrodes with a large surface area and enhanced mass transfer. Furthermore, stabilization processes associated with electrochemical dissolution and sulfur crossover through the membrane induced specific changes in the chemical and physical properties of the electrodes after electrolysis. This study demonstrates that NF-based electrocatalysts can be incorporated in an efficient electrochemical flow cell system for sulfite electrolysis and hydrogen production, with potential applications at a large scale.

Self-Limiting Growth of Two-Dimensional Palladium between Graphene Oxide Layers.

The ability of different materials to display self-limiting growth has recently attracted an enormous amount of attention because of the importance of nanoscale materials in applications for catalysis, energy conversion, (opto)electronics, and so forth. Here, we show that the electrochemical deposition of palladium (Pd) between graphene oxide (GO) sheets result in the self-limiting growth of 5-nm-thick Pd nanosheets. The self-limiting growth is found to be a consequence of the strong interaction of Pd with the confining GO sheets, which results in the bulk growth of Pd being energetically unfavorable for larger thicknesses. Furthermore, we have successfully carried out liquid exfoliation of the resulting Pd-GO laminates to isolate Pd nanosheets and have demonstrated their high efficiency in continuous flow catalysis and electrocatalysis.

Electrodeposition of Pd-Pt Nanocomposites on Porous GaN for Electrochemical Nitrite Sensing.

In recent years, nitrite pollution has become a subject of great concern for human lives, involving a number of fields, such as environment, food industry and biological process. However, the effective detection of nitrite is an instant demand as well as an unprecedented challenge. Here, a novel nitrite sensor was fabricated by electrochemical deposition of palladium and platinum (Pd-Pt) nanocomposites on porous gallium nitride (PGaN). The obtained Pd-Pt/PGaN sensor provides abundant electrocatalytic sites, endowing it with excellent performances for nitrite detection. The sensor also shows a low detection limit of 0.95 µM, superior linear ampere response and high sensitivity (150 µA/mM for 1 to 300 µM and 73 µA/mM for 300 to 3000 µM) for nitrite. In addition, the Pd-Pt/PGaN sensor was applied and evaluated in the determination of nitrite from the real environmental samples. The experimental results demonstrate that the sensor has good reproducibility and long-term stability. It provides a practical way for rapidly and effectively monitoring nitrite content in the practical application.

Graphene-Palladium Composite for the Simultaneous Electrochemical Determination of Epinephrine, Ascorbic acid and Uric Acid

The unique properties of graphene blended with palladium deposition were used for sensing application by virtue of its charge transfer properties. Epinephrine (EP) is anodically oxidized on a glassy carbon electrode (GCE) modified by palladium graphene composite in phosphate buffer solution of pH 7. The electrodeposited palladium over the GCE – graphene surface ensures fast electrochemical determination of EP. The electrode served as a sensing platform for the simultaneous voltammetric determination of EP, ascorbic acid (AA) and uric acid (UA). The electrochemical deposition of palladium has greatly enhanced the surface properties. Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry were used to assess the electrochemical performance. Investigations reveal that the process is adsorption controlled involving two electrons and the average catalytic rate constant is 2.39 × 103 M−1s−1. Palladium incorporated electrode sensitively determined EP in presence of the usual interferents uric acid (UA) and ascorbic acid (AA) with well resolved peaks at very minute concentrations. DPV method enabled the highest sensitivity of 100nM for EP, 170nM for UA and 22μM for AA. The modified electrode offered excellent performance toward real samples such as blood serum and urine.

Elimination of the interfering effect of hydrogen on the determination of palladium by stripping voltammetry

The effect of hydrogen on the electrooxidation current of a palladium–hydrogen precipitate is studied. It is shown that the UV irradiation of the solution changes the mechanism of the formation of molecular hydrogen in the electrochemical deposition of palladium. A procedure is developed for determining palladium in platinum metal preconcentrates by stripping voltammetry.

Electrochemical Palladium Deposition on Titanium Nitride, Ruthenium and Palladium Substrates for Nanoscale Device Fabrication

With the advances in device fabrication, scaling of electrochemical techniques to molecular scale is becoming essential. Electrochemical deposition of metals in devices with nanoscale dimensions can play an integral role in reducing critical dimensions of such devices. This study focuses on electrochemical deposition of palladium on substrates such as titanium nitride, ruthenium and palladium that are commonly used in manufacturing of nanoscale devices such as nanochannels and nanopores. Palladium is used in many applications ranging from electrochemical biosensors to catalysts in electronic and optoelectronic devices (1, 2). Electrochemical deposition of palladium is preferred in many of these applications as a result of ease of manufacturing, controllability and economics.Cyclic voltammetry and hydrodynamic linear sweep voltammetry were used to understand the effects of electrolyte composition and operating conditions on palladium electrodeposition. Blanket samples of titanium nitride, ruthenium and palladium were plated to study nucleation of palladium on these substrates. It was observed that high nucleus densities could be achieved on all three substrates under optimal operating conditions and electrolyte compositions. Ruthenium and palladium substrates behaved similarly in the electrolytes used in this study whereas titanium nitrite behavior was different.To study palladium plating in small openings two test vehicles were designed. The first test vehicle (panel A) had metal lines buried under oxide layers and the second test vehicle (panel B) had metal lines without the oxide capping layer. Transfer of knowledge from beaker-scale experiments on blanket samples and electroanalytical techniques to plating in these test vehicles will be presented.

Electrochemical Palladium Deposition for Reducing Critical Dimensions in Nanostructures

Electrochemical deposition of metals in devices with nanoscale dimensions can play an integral role in reducing critical dimensions of such devices and address challenges faced in microfabrication for miniaturization. This study focuses on electrochemical deposition of palladium on substrates such as titanium nitride, ruthenium and palladium that are commonly used in manufacturing of nanoscale devices such as nanochannels and nanopores. Cyclic voltammetry and hydrodynamic linear sweep voltammetry were used to understand the effects of electrolyte composition and operating conditions on palladium electrodeposition. Blanket (non-patterned wafer) samples of titanium nitride, ruthenium and palladium were plated to study the nucleation of palladium on these substrates and to understand nucleation trends at different operating conditions and electrolyte compositions. To study palladium plating in small openings, two test vehicles were designed. The first test vehicle had metal lines buried under oxide layers with 26 nm openings. The second test vehicle had interconnect-like metal lines with 90 nm spacing between the lines. Transfer of knowledge from beaker-scale experiments on blanket samples and electroanalytical techniques to plating in these test vehicles will be presented. For the first test vehicle the critical dimensions were reduced from 26 nm to 12 nm and for the second vehicle from 90 nm to 51 nm.

Amperometric detection of ascorbic acid in honey using ascorbate oxidase immobilised on amberlite IRA-743

Abstract A differential amperometric method for the specific determination of ascorbic acid in honey was developed by association of a flow injection analysis (FIA) system and a tubular reactor containing the ascorbate oxidase enzyme immobilised. A gold electrode modified by electrochemical deposition of palladium was employed as working electrode. Ascorbic acid was quantified in seven samples of commercial honeys using a potential of +0.60 V vs. Ag/AgCl (sat) . The linear dynamic range in ascorbic acid extends from 1 to 50 μmol L −1 , at pH 7.0. At flow rate of 1.5 mL min −1 and injecting 250 μL sample volumes, a sampling frequency of 180 determinations per hour is afforded. The detection and quantification limit of this method are 0.14 and 0.49 μmol L −1 , respectively. The samples analyses were compared with the volumetric method, and showed an excellent correlation between the methods.

Palladium Electrodeposition on Carbon Black Films in an Acid Environment

Electrochemical deposition of palladium on nanostructured carbon black films electrodes (nCBFE) supported in glassy carbon (GC) was studied by cyclic voltammetry of reversal potential (E lambda), chronoamperometry and the anodic stripping voltammetry techniques in the electrolytic system 10-3M PdCl2; 1M NH4Cl pH=0. The cyclic voltammetry studies allowed us to characterize the electrochemical response of nCBFE and establish that it can be used as an electrode material for palladium electrodeposition. The chronoamperometry and anodic stripping voltammetry studies allowed us to define a specific potential range for palladium deposition without hydrogen evolution (-0.09 to -0.19 V vs. SCE). It should be noted that the hydrogen discharge takes place at more negative potentials. Moreover, it was possible to evaluate the corresponding mass of metallic palladium in a wide potential range with and without hydrogen discharge influence.

Electrocrystallization of palladium from Pd(NH3)4Cl2 bath on stainless steel 316L

Electrochemical deposition of palladium from 0.04 M Pd(NH3)4Cl2, NH4Cl, and NH4OH bath (pH = 10) on stainless steel electrode was studied by voltammetry, chronopotentiometry, and chronoamperometry. Crossovers in cyclic voltammograms demonstrate that the deposition of palladium proceed via a nucleation/growth mechanism. Chronopotentiograms indicate that palladium reduction is not controlled by diffusion and Sand’s law is not obeyed. In the early stage of the deposition, two-dimensional (2D) nucleation and growth proceeding through instantaneous and a multitude of progressive steps followed the initial double layer charging. The processes are manifested as broad maxima in chronoamperogram and after which the current transient terminates to a plateau. Non-linear fitting methods were applied to obtain the kinetic parameters in the light of Bewick, Fleischmann, and Thirsk theory for 2D and Armstrong, Fleischmann, and Thirsk model for 3D nucleation and growth process.

Polypyrrole/palladium composites for the electrocatalyzed Heck reaction

Composite layers of palladium particles embedded in polypyrrole are formed in a two-step process: electropolymerization of pyrrole followed by an electrochemical deposition of palladium from Pd(OAc) 2 solution. These composites are suitable as a heterogeneous catalyst for the Heck reaction. The catalytic reaction of chloro-, bromo- and iodo-benzene with styrene to form trans-stilbene is studied. It is demonstrated that the Heck reaction can be driven electrochemically. The catalysis is analyzed by spectroelectrochemistry in parallel geometry and gas chromatographic analysis of the solution. The mechanism of the electrochemical driven Heck reaction is discussed.

Second harmonic generation study on electrochemical deposition of palladium on a polycrystalline gold electrode

Electrochemical deposition (electrodeposition) and dissolution processes of Pd on a polycrystalline Au electrode surface in HClO 4 solution containing PdCl 4 2− were investigated by second harmonic generation (SHG) measurements. Both 1064 nm (near-IR) and 600 nm (visible) excitations were employed to monitor the SHG behavior in situ. Under the near-IR excitation, the resulting SHG signal contained contributions from both the Pd deposit and the adsorbed PdCl 4 2−. On the other hand, the adsorption of the PdCl 4 2− did not affect the SHG signal under the visible excitation. The SHG signal under the visible excitation was resonantly enhanced with the first and second monolayer depositions of Pd but declined with higher Pd coverage. These results confirm the unique structure and property of an ultra-thin Pd overlayer on gold, suggested by scanning tunneling microscopy (STM), surface X-ray scattering (SXS) and electrochemical measurements at electrodeposited Pd thin layers on single crystalline gold surfaces.

Influence of humidity and hydrogen on the charge transport in p-InP diode structures with a palladium contact

The p-InP-n-In2O3-P2O5-Pd diode structure was fabricated using a two-stage technological procedure, which involved cold etching, polishing, and electrochemical deposition of palladium. The charge transport is investigated in the temperature range of 110–300 K, and the current-voltage characteristics are explained in terms of tunneling through a barrier, over deep trapping centers, and band-to-band tunneling. It is found that the open-circuit photovoltage increases in a water vapor atmosphere. It is demonstrated that this effect is defined by the variation of the recombination kinetics via bound states on the n-In2O3-P2O5 heteroboundary because of the absorption of H2O molecules in P2O5 oxide. The open-circuit photovoltage increases linearly with the water vapor concentration, and the relaxation of the photovoltage pulse takes ∼1–2 s. Photovoltage relaxation for the forward and reverse currents after the action of H2 is investigated. The data obtained revealed the possibility of devising a detector of threefold application, namely, for detecting near-infrared radiation, humidity, and hydrogen.

Initial stages of Pd deposition on Au(hkl) Part I: Pd on Au(111)

The electrochemical deposition of palladium onto Au(111) from chloride-containing solutions was investigated by in-situ STM and cyclic voltammetry. These methods are complementary by yielding structural and thermodynamic information. For [PdCl 4] 2− adsorbed on Au(111), a distorted hexagonal structure was imaged, and a phase transition within this adsorbed layer was observed. This palladate anion was found to play a crucial role in Pd deposition and dissolution. Pd deposition starts by forming a pseudomorphic layer in the underpotential region, followed by the formation of a second Pd monolayer at overpotentials. By using stepped Au(111) surfaces, an assignment of voltammetric peaks to nucleation of Pd at steps and on terraces was achieved. It is generally observed that Pd nucleates at monoatomic high steps and grows two-dimensionally. The morphology of the overlayers changes with increasing Pd coverage from flat and well-ordered for the first two monolayers to increasingly rough and defect-rich, but retaining Pd(111) characteristics in cyclic voltammetry up to at least 10 monolayers.

Flow injection analysis-amperometric determination of ascorbic and uric acids in urine using arrays of gold microelectrodes modified by electrodeposition of palladium

Uric acid (UA) and ascorbic acid (AA) present in urine were rapidly determined by the amperometric method in association with flow injection analysis. An array of gold microelectrodes modified by electrochemical deposition of palladium was employed as the working electrode. Uric and ascorbic acids were quantified in urine using amperometric differential measurements at +0.75 and +0.55 V, respectively. This method is based on three steps involving the flow injection of: (1) the sample spiked with a standard solution, (2) the pure sample, and (3) the enzymatically treated sample. The enzymatic treatment was carried out with ascorbate oxidase, uricase, and peroxidase at pH 7. The calibration curves for freshly prepared ascorbic and uric acid standards were very linear in the concentration ranges of 0.44–2.64 mg l −1 (AA) and of 0.34–1.68 mg l −1 (UA) with a relative standard deviation (RSD) <1 %. For uric acid, the real sample analyses where compared with the classical spectrophotometric method, showing deviations between 3.1 and 8.6% ( n = 9).

Epitaxial growth of a palladium layer on an Au(100) electrode

Abstract The electrochemical deposition process of palladium from a PdCl42− complex on an Au(100) substrate was investigated using in situ scanning tunneling microscopy (STM). The reactant, i.e. the PdCl42− complex, was found to adsorb on the Au(100) surface with an ordered structure in the potential region where neither a cathodic nor an anodic current flowed. The electrochemical deposition of palladium on the Au(100) proceeded at potentials more negative than 1.0 V. The electrodeposition of the first palladium layer started not only on the terrace but also on gold islands which were formed as a result of the lifting process of the reconstructed Au(100) surface and then proceeded two-dimensionally. The following palladium layer was found to grow mainly from the deposited palladium region on top of the gold islands. The shape of the gold island could be identified even after four palladium layers were deposited. The bulk and surface structures of the deposited palladium layer were characterized by X-ray diffraction (XRD) and the copper underpotential deposition (upd) reaction, respectively, and the formation of the Pd(100) phase with a (1×1) surface structure was confirmed.

Electrochemical deposition of palladium on an Au(111) electrode: effects of adsorbed hydrogen for a growth mode

Electrochemical deposition of palladium on an Au(111) electrode was investigated using in situ scanning tunneling microscopy (STM) and electrochemical quartz crystal microbalance (EQCM). STM images clearly showed that palladium deposition was proceeded two-dimensionally even in the relatively large overpotential region up to ∼+0.3 V (vs. RHE). Many nuclei were created, however, in the potential region where hydrogen adsorption took place, i.e. more negative than +0.3 V. EQCM measurement showed that the surface mass was steadily increased during the potential scan as far as the cathodic current flowed even in the potential region where hydrogen adsorption took place. The abrupt surface mass decrease and increase were observed, however, when the potential was stepped from +0.4 V (hydrogen desorbed state) to +0.1 V (hydrogen adsorbed state) and from +0.1 to +0.4 V, respectively, showing the desorption and adsorption of PdC1 4 2− complex from the electrode surface upon hydrogen adsorption and desorption, respectively. These results support the model that the PdCl 4 2− complex plays an important role to inhibit the three-dimensional growth and facilitate the two-dimensional growth.

Flow-injection analysis of glucose at an amperometric glucose sensor based on electrochemical deposition of palladium and glucose oxidase on a glassy carbon electrode

A glassy carbon electrode (GCE) modified with palladium provides excellent electrocatalytic oxidation of hydrogen peroxide. When the electrolyte contains palladium chloride and glucose oxidase, the GCE can be modified by electrochemical codeposition at a given potential. The resulting modified surface was coated with a thin film of Nafion to form a glucose sensor. Such a glucose sensor was successfully used in the flow-injection analysis of glucose with high stability and anti-poisoning ability. It gave a detection limit of 1 × 10 −7 M injected glucose, with a linear concentration range of 0.001–8 mM. There is no obvious interference from substances such as ascorbate and saccharides.

The absorption of hydrogen and deuterium in thin palladium electrodes: Part II: Basic solutions

A comparative study of hydrogen and deuterium sorption in Pd from basic solutions (0.1 M NaOH, NaOD, LiOH and LiOD) has been performed, using electrodes obtained by electrochemical deposition of palladium on gold. The amount of absorbed hydrogen or deuterium has been found to depend on the electrode potential. The shape of H(D)/Pd vs. E plots and the rate of hydrogen (or deuterium) absorption are strongly influenced by the composition of the solution. Lithium appears to have a marked influence on the α to β phase transition. The maximum H(D)/Pd ratios were about 0.8 for all studied solutions. The greater isotopic effect has been found during absorption and desorption in lithium solutions. 1. 1. The amount of absorbed hydrogen-deuterium in the bulk of palladium depends on the electrode potential. 2. 2. The shape of the plots of absorbed hydrogen amount from basic solutions vs. absorption potential strongly depends on composition of solution and significantly differs from the shape of the same plots in acidic solution (2). The results show that alkali metal cations markedly influence hydrogen and deuterium sorption processes. 3. 3. Lithium ions seem to affect the α-β transition more than sodium ions. 4. 4. The isotopic effect is much stronger during oxidation of absorbed hydrogen than during absorption. This effect is greater in lithium solutions. 5. 5. No significant influence of solution composition on the maximum values of the H(D)/Pd ratios has been found. 6. 6. The charging curves in all the solutions studied are not reversible, as was the case in acidic solutions. This means that the sorption or desorption causes irreversible changes in the Pd lattice.

Electrochemical in‐situ investigations on polycrystalline gold electrodes with oscillating quartz crystals: Deposition and bulk diffusion of palladium

AbstractThe electrochemical deposition of palladium on polycrystalline gold substrates was followed in the UPD range and under conditions where massive metal deposition occurs. These processes were studied by means of in‐situ microweighing, cyclic voltammetry and the registration of frequency and current with time. In addition, the diffusion kinetics of palladium into the gold substrate was studied under UPD conditions. The latter process leads to alloy formation. The electrosorption valency γ for palladium adsorbates was determined to be γ = 1.8. The apparent diffusion coefficient D of palladium into the gold electrode yields D ≈ 10−17 cm2/s for the conditions applied here.