Electroless Deposition Of Pd Research Articles

Carbon screen-printed electrodes for substrate-assisted electroless deposition of palladium

Five types of carbon-based screen-printed electrodes (SPE) – carbon (C110), mesoporous carbon (MC), single walled carbon nanotubes (SWCNT)-, carbon nanotubes (CNT)-, and carbon nanofibers (CNF)-modified electrodes – are characterized with respect to surface roughness, true surface area (TSA), electrochemical activity and electrochemical impedance (EIS) behavior and further used for electroless deposition of Pd. Structural characterization was performed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Investigation of the surfaces with AFM revealed an increasing root mean square (RMS) roughness in the order C110, SWCNT, CNT, CNF, and MC. EIS studies demonstrate significant difference in the resistance of the SPEs with largest value found for the carbon electrode (C110), followed by the carbon nanofiber (CNF)-modified electrode. MC, CNT- and SWCNT-modified electrodes exhibit close, significantly lower resistance values. The capacitance of the carbon-based SPEs is found to be rather high for all electrodes even if accounting for the TSA which has been determined with AFM. This implies a significant effect of nanoroughness and/or of a large internal porous structure especially for CNF and MC SPEs. Pd electroless deposition occurs at all carbon-based SPEs after reductive pre-treatment in supporting electrolytes (0.5 mol dm−3 H2SO4 or 0.1 mol dm−3 LiClO4) without using a solute chemical reductant in the metal plating solution. The amount and characteristics of the deposited Pd is estimated by anodic stripping voltammetry, EDX analysis, and SEM. It is established that the type and amount of Pd deposit depends on the structure of the carbon-based electrodes with nanostructured carbon coatings (consisting of CNT, SWCNT, or CNF) providing higher amounts of deposited Pd (in the range of 4.4 to 5.8 µg cm−2) and smaller size of the obtained metal particles.

Palladinized graphene oxide-MOF induced coupling of Volmer and Heyrovsky mechanisms, for the amplification of the electrocatalytic efficiency of hydrogen evolution reaction

In this study, a nanocomposite of palladium supported graphene oxide (GO)/metal–organic framework (MOF) was prepared using electroless deposition of Pd on GO followed by impregnation method of Pd@GO and MOF. The prepared materials were characterized with various analytical techniques and their applications as HER electrocatalysts were evaluated using cyclic voltammetry (CV), Tafel plots, and turn over frequencies (TOFs). The HER results showed a radical increment of H2 production in the nanocomposite through the Volmer reaction together with Heyrovsky or Tafel mechanism. This disclosed that the addition of Pd@GO/MOF in the electrolytic system possessed better catalytic characteristics with enhanced current density which may open a new way for hydrogen production and storage via HER.

PEDOT-supported Pd nanocatalysts – oxidation of formic acid

Palladium (Pd) nanocatalysts are obtained by electroless deposition of Pd on pre-reduced poly(3,4-ethylenedioxythiophene) (PEDOT) layers doped with either polystyrenesulfonate (PSS) or dodecylsulfate (SDS) ions. The PEDOT-supported Pd catalysts are investigated with respect to formic acid (FA) oxidation in slightly acidic solution under voltammetric and chronoamperometric conditions. Atomic force microscopy (AFM) and Scanning electron microscopy (SEM) studies are carried out before and after exposure to FA. It is established that the dopant used for the synthesis of PEDOT does affect not only the distribution of the Pd nanoparticles on the polymer surface but also the stability of the composites upon electrochemical treatment in the presence of FA. It is found that PEDOT-PSS undergoes structural rearrangement, and significant loss of the Pd catalyst is observed. In comparison, PEDOT-SDS is more resistant to FA exposure since aggregated Pd nanoparticles are providing additional stability of the polymer structure.

Hydrogen in Electrolessly Deposited Ni/Au and Ni/Pd/Au Films

For the surface finishing of copper layer on printed circuit boards, autocatalytic electroless deposition of nickel-phosphorus alloy and immersion deposition of gold (ENIG, Ni-P/Au) or autocatalytic electroless deposition of Ni-P, palladium and immersion deposition of Au (ENEPIG, Ni-P/Pd/Au) are widely used. The Ni-P/Pd/Au surface finish is suitable not only for lead-free soldering but also for wire bonding [1]. For soldering, it was reported that hydrogen plasma improved bonding behavior and realized a flux-free process [2]. Electrochemically deposited metal films include hydrogen atoms. The hydrogen adsorbed in metal films causes various phenomena such as atomic diffusion, alloying, crystal growth, void formation. We have been investigating the atomistic state and behavior of hydrogen in electrodeposited metals by thermal desorption spectroscopy [3, 4]. In this study we measured changes in hydrogen amounts in the Ni-P/Au and Ni-P/Pd/Au surface finishes [5]. We used two different electroless Pd baths using formic acid (Ni-P/Pd/Au) and sodium phosphinate (Ni-P/Pd-P/Au) as reducing agents. The Ni-P films contained large amounts of diffusible hydrogen that desorbs at room temperature. During autocatalytic electroless deposition of Pd and Pd-P on Ni-P films, the greater part of the hydrogen in the Ni-P films desorbed. Although no hydrogen evolution accompanied immersion Au deposition, the hydrogen amounts in Ni-P/Au, Ni-P/Pd/Au, and Ni-P/Pd-P/Au films were much greater than in films without a Au layer. Moreover, at room temperature, they remained almost unchanged for one month after deposition, indicating that the thin Au layer (< 0.1 μm) prevents hydrogen desorption from the metal films. The high hydrogen concentration in Ni-P/Au films improved solder wettability.[1] Y. Oda, M. Kiso, S. Kurosaka, A. Okada, K. Kitajima, and S. Hashimoto, Proc. Internal. Microelectronic and Packaging Soc., IMAPS (2008).[2] T. Hagihara, T. Takeuchi, and Y. Ohno, Proc. 10th Electronics Packaging Technology Conf. (IEEE), 595 (2008).[3] N. Fukumuro, S. Kojima, M. Fujino, Y. Mizuta, T. Maruo, S. Yae, and Y. Fukai, J. Alloy. Comp., 645, S404 (2015).[4] N. Fukumuro, K. Tohda, and S. Yae, this symposium.[5] Y. Oda, Y. Sagara, N. Fukumuro, and S. Yae, J. Surf. Finish. Soc. Jpn., 70, 163 (2019).

Pd-coated Ru nanocrystals supported on N-doped graphene as HER and ORR electrocatalysts.

Here, Pd-coated Ru nanocrystals supported on N-doped graphene (Pd-Ru@NG) are obtained via electroless deposition of Pd on Ru nanocrystals. We have demonstrated that Pd boosts the electrocatalytic performance of Pd-Ru@NG towards the hydrogen evolution reaction (HER) and alcohol tolerant oxygen reduction reaction (ORR) as compared to Pt/C.

Graphite electrode-assisted electroless deposition of palladium in the absence and presence of poly(3,4-ethylenedioxythiophene) coatings

Electroless deposition of Pd in the absence of solute reducing species is studied on pre-reduced non-coated and poly(3,4-ethylenedioxythiophene)(PEDOT)-coated graphite electrodes. PEDOT coatings doped with either dodecyl sulfate (SDS) or polysterene sulfonate (PSS) ions are used in the studies. Electrochemical reductive pre-treatment occurs at negative enough potential to initiate hydrogen reduction at the modified electrodes. Large amounts of deposited Pd significantly exceeding the quantity that is expected to be reduced at the expense of PEDOT re-oxidation alone are found to deposit irrespective of the polymer coating’s thickness. Pd particles are observed to deposit also at bare pre-reduced graphite electrode. It is suggested that molecular hydrogen entrapped during the reductive treatment plays the role of additional reductant for the electroless Pd deposition. SEM, UV–vis and Raman investigations are used to study possible structural changes of PEDOT provoked by the strong reductive treatment. The data give evidence for irreversible structural change in the PEDOT/SDS case resulting in a dense morphology that inhibits ionic transport and supports Pd electroless deposition.

Electroless deposition of palladium nanoparticles on poly(3,4-ethylene-dioxythiophene)—role of the electrode substrate

Electroless deposition of Pd is studied comparatively on glassy carbon (GCE) and spectral graphite (SGE) electrodes modified with electrodeposited poly(3,4-ethylene-dioxythiophene) (PEDOT) layers. Computed microtomography is used to explore the bulk structure of both types of carbon electrodes. It is found that SGE has high (27%) open porosity in contrast to GCE, the latter characterized by a dense and homogeneous structure with no porosity. Despite the structural difference of the electrodes, the intrinsic electrochemical activity of PEDOT is found to remain unaffected by the type of the underlying carbon substrate used for PEDOT electrochemical deposition. Electroless deposition of Pd is carried out on pre-reduced PEDOT-coated electrodes, in the absence of additional reductants in the electrolyte solution and expected to occur at the expense of PEDOT oxidation. It is found that at constant polymerization charge of PEDOT, the amount of metal deposited on PEDOT/SGE is several times higher in comparison to PEDOT/GCE. The high effectiveness for electroless metal deposition on PEDOT/SGE is explained by the involvement of pre-reduced hydrogen embedded in the highly porous structure of SGE that acts further as additional (apart from PEDOT) reductant contributing markedly to the amount of reduced Pd ions.

High-density Pd nanoparticles distribution on PEDOT obtained through electroless metal deposition on pre-reduced polymer layers

Pd electroless deposition is carried out at the expense of oxidation of pre-reduced poly(3,4-ethylene dioxythiophene) (PEDOT)-coated electrodes. Two largely differing potentials for deep and mild pre-reduction of PEDOT are chosen and correspond to initial low (deep pre-reduction) and, correspondingly, high (mild pre-reduction) conductive states of the polymer material. The role of organic doping ions (polysterene sulfonate, PSS or dodecyl sulfate, SDS) used in the course of PEDOT synthesis for the electroless deposition of Pd is also investigated. PEDOT-supported Pd catalysts with high-density homogeneous distribution of Pd nanoparticles (NPs) with sizes ranging between 4 and 12nm are obtained. The amount of deposited metal depends significantly on the pre-reduction potential of PEDOT whereas the surface density of the metal NPs is largely influenced by the doping ions used to obtain the PEDOT material. Evidence for irreversible structural transformation obtained upon deep pre-reduction of PEDOT:SDS is obtained.

Size-Controlled Pd Nanoparticle Catalysts Prepared by Galvanic Displacement into a Porous Si-Iron Oxide Nanoparticle Host.

Porous silicon nanoparticles containing both Pd and iron oxide nanoparticles are prepared and studied as magnetically recoverable catalysts for organic reductions. The Pd nanoparticles are generated in situ by electroless deposition of Pd(NH3)42+, where the porous Si skeleton acts as both a template and as a reducing agent and the released ammonia ligands raise the local pH to exert control over the size of the Pd nanoparticles. The nanocomposites are characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, nitrogen adsorption, X-ray diffraction, superconducting quantum interference device magnetization, and dynamic light scattering. The nanocomposite consists of a porous Si nanoparticle (150 nm mean diameter) containing ∼20 nm pores, uniformly decorated with a high loading of surfactant-free Pd nanoparticles (12 nm mean diameter) and superparamagnetic γ-Fe2O3 nanoparticles (∼7 nm mean diameter). The reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride is catalyzed by the nanocomposite, which is stable through the course of the reaction. Catalytic reduction of the organic dyes methylene blue and rhodamine B is also demonstrated. The conversion efficiency and catalytic activity are found to be superior to a commercial Pd/C catalyst compared under comparable reaction conditions. The composite catalyst can be recovered from the reaction mixture by applying an external magnetic field due to the existence of the superparamagnetic iron oxide nanoparticles in the construct. The recovered particles retain their catalytic activity.

Electroless Pd deposition on a planar porous stainless steel substrate using newly developed plating rig and agitating water bath

A new plating bath was developed to prevent palladium plating in the pores of the porous stainless steel support when using plate-type porous substrate. The plating bath, composed of a holder, a rubber O-ring and a bottom, provides very simple assembly and is very effective in preventing palladium plating in the pores of porous stainless steel. The agitation of the plating solution increases plating rate significantly because the agitation improves the external mass transfer of Pd ion and reducing agent to the membrane surface facilitating ~99.7% plating yield of palladium ion. This new plating method carried out at a temperature range of 293 to 298 K provides a very simple and economic membrane manufacturing process. Using a newly developed plating rig, an 88.9-mm diameter membrane was fabricated, and gas permeation tests showed that the hydrogen permeation flux reached ~0.9 mol s−1 m−2 at 873 K and a pressure difference of 300 kPa and selectivity (H2/N2) was ~1,850 at 873 K with a pressure difference of 100 kPa.

Communication—Reaction Processes in Electroless Pd Deposition on Ni-P Surfaces Utilizing Formic Acid as Reducing Agent

Herein, electroless Pd deposited on Ni-P surfaces using formic acid (FA) as a reducing agent was investigated. Open circuit potential with time (OCPT) and cyclic voltammetry (CV) results suggest that electroless Pd deposited on Ni-P surfaces occurs by a two stage reaction. First, Pd plating proceeds via a galvanic displacement reaction between Ni and Pd2+. Subsequently, Pd deposited via autocatalytic reaction takes place on Pd surfaces. When the displacement reaction was prevented, the autocatalytic deposition of palladium was incapable of proceeding; therefore, it is confirmed that the displacement reaction is a necessary prerequisite for occurrence of the autocatalytic reaction.

Chemiresistive hydrogen gas sensors from gold-palladium nanopeapods

Gold-palladium (Au-Pd) nanopeapod-based H2 chemiresistors were fabricated using a gold binding M13 viral template. Peptides displayed along the length of this biological template served as affinity binding sites to direct gold nanoparticle assembly under ambient conditions in an aqueous environment. In addition, the geometry of this filamentous biomolecule readily facilitated the formation of the highly anisotropic nanopeapod structure. Pd electroless deposition controlled peapod diameter, as well as electrical resistance. Sensor performance was determined by overall peapod morphology. Thicker nanopeapods (i.e., ∼15 nm Pd layer) with fully encapsulated Au nanoparticle seeds showed strong evidence of oxygen inclusion during or after Pd deposition, and a modest response (i.e., 0.04%–2.6%) at 2000 ppmv H2 after device conditioning through extended H2 exposure. Thinner nanopeapods (i.e., ∼5 nm Pd layer) with discontinuous Au nanoparticle coverage showed superior performance with a response of 117% at 2000 ppmv H2 in air, a 70% response time (t70%) within 1 min, and a low detection limit of 25 ppmv. The bio-directed formation of these unique thin-shelled, Au-Pd peapod nanostructures and the development of a highly sensitive H2 detector advance both the fields of nanoassembly and gas sensing.

Surface functionalized TiO2 supported Pd catalysts for solvent-free selective oxidation of benzyl alcohol

Pd catalysts supported on TiO2 functionalized with various amounts of 3-aminopropyltriethoxysilane (APTES) were prepared using a post-synthesis grafting method combined with electroless deposition of Pd. As revealed by the Fourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) results, monolayer APTES grafting was obtained using 0.005mmol APTES on 1.5g TiO2 support. Excess amounts of APTES resulted in both multilayer and reversed attachment, which NH2 attached to the TiO2 surface rather than giving free NH2 termination. The catalytic activity in the solvent-free selective oxidation of benzyl alcohol was correlated well with the highest amount of Pd deposited as well as the formation of small and uniform Pd nanoclusters with narrow particle size distribution (average diameter 3.4nm) on the 1%Pd/TiO2-0.005APTES. Increasing of surface basicity via the hydrolysis of amino groups (NH2) is suggested to enhance the dehydrogenation of benzyl alcohol, and as a consequence the selectivity toward benzaldehyde increased for all the APTES-modified TiO2 supported Pd catalysts. In addition, the combination of metallic Pd0 and PdOx (Pd2+/Pd4+) species gave high catalytic activity in the benzyl alcohol oxidation, emphasizing that the reduction of PdOx species by the adsorbed benzyl alcohol is an essential step to form highly active metallic Pd0 sites.

Synthesis and Properties of “Black Silicon” Formed by Pd-Catalyst Etching in NH4HF2/H2O2 Solution

An etching system NH4HF2/H2O2 was developed to fabricate porous columnar structure on Si surfaces. The Pd catalyst was electroless-deposited on Si wafers in aqueous HF (5%) solution containing PdCl2. The PdCl2 concentration was varied from 0.001 to 0.04 mol/L and various etching conditions were optimized. The structural and optical properties of the catalytic-etched samples were investigated by scanning electron microscopy, wettability observation, Fourier-transform infrared spectroscopy analysis, near-IR−visible transmittance, photoluminescence (PL), and Raman scattering measurements. Vertically well-aligned columnar structure was formed in the limited conditions of electroless Pd deposition and subsequent catalytic etching. Such columns also formed a “macroporous” structure, in direct contrast to the case of the HF/AgNO3 etching (i.e., “dense” nanowires). No strong PL emission was observed from the present samples. The Raman scattering intensities were much stronger with more asymmetric and broader spectral features than that for the bulk Si wafer. Such Raman spectra were well interpreted by a modified Lorentzian line-shape model. Passive HF etching of the catalytic-etched surface changed wettability from superhydrophilic (∼0°) to highly hydrophobic (∼140°). The catalytic-etched Si samples were also found to exhibit “black silicon” in nature.

Combining Electroless Filling with Metal-Assisted Chemical Etching to Fabricate 3D Metallic Structures with Nanoscale Resolutions

Thisworkintroducesasimpleprocesstofabricate3Dmetallicstructureswithmicrotonano-sizedfeatures.Star-shapedgoldcatalysts were fabricated using electron beam lithography and used as catalysts in MaCE to form spiraling 3D structures. High fidelity was verified by adding 30 nm wide holes in some catalysts for form 30 nm wide spiraling silicon pillars. The gold catalyst remaining at the bottom of the 3D MaCE template was used as a seed for electroless deposition of Pd and the resulting structure extracted using

Application of surface-modified metal hydrides for hydrogen separation from gas mixtures containing carbon dioxide and monoxide

Abstract Application of surface-modified MH material for H 2 separation using temperature/pressure swing absorption–desorption was studied. The substrate alloy had the following composition LaNi 3.55 Co 0.75 Al 0.4 Mn 0.3 , and the surface modification was carried out through fluorination followed by aminosilane functionalization and electroless deposition of Pd. The material was found to have good poisoning tolerance towards surface adsorbates, even for the large (∼1.5 kg) batches. Feasibility of its application for H 2 separation from gas mixtures (up to 30% CO 2 and 100 ppm CO) was demonstrated by testing of a prototype H 2 separation system (∼280 g of MH in two reactors), and H 2 separation reactor (0.75 kg of MH). The H 2 separation was characterized by stable performances in the duration of 250 absorption/desorption cycles. However, the total process productivity was found to be limited by the sluggish H 2 absorption (partial H 2 pressure ⩽2.5 bar, temperature below 100 °C). In the presence of CO 2 and CO, additional deceleration of H 2 absorption was observed at space velocities of the feed gas below 5000 h −1 .

Electroless plated SnO2–Pd–Au composite thin film for room temperature H2 detection

Extremely thin SnO2 nanosheets with high surface area were fabricated through a one-pot hydrothermal method. In this work, gas sensing property of the SnO2 nanosheets was studied. SnO2–Pd–Au mixed thin films were prepared by electroless deposition of Pd, Au, and nanostructured SnO2 onto the surface of a high resistance alumina substrate. The whole fabrication process was carried out at room temperature without any thermal treatment required. The films deposited on the alumina substrate were characterized by SEM and EDS. The co-deposited Au improved the electric conductance of the sensing film. A relatively large amount of Pd (Pd/Sn ratio around 1:1) was obtained for the film instead of the usually low doping value of Pd (∼0.1% level) for SnO2 hydrogen sensor. It has been found that the SnO2–Pd–Au composite film sensor has fast response in the range of 134–1469ppm toward hydrogen gas at room temperature. The sensor also shows good stability and repeatability. Effects of annealing condition of the sensing film on H2 gas sensing performance was investigated as well. A possible machnism for SnO2–Pd room temperature hydrogen sensing is proposed.

Ultrathin palladium membranes prepared by a novel electric field assisted activation

Ultra-thin Pd composite membranes with a thickness of 1 μm were prepared by a novel electric-field assisted activation technique followed by electroless deposition of Pd on a hollow-fiber α-alumina support. The novel activation method places Pd precursors and a reducing agent on opposite sides of a porous substrate and uses an electric field to cause migration of Pd ions to the outer surface where they are reduced to form seeds in high density in a narrow spatial region. The resulting membranes showed a high hydrogen permeance in the range of 4.0–5.0 × 10 −6 mol m −2 s −1 Pa −1 and stable H 2/N 2 selectivity of 3000–9000 during stability tests for 150 h at 733 K with H 2 flow. The formation of the thin, defect-less and robust Pd layer can be ascribed to the evenly distributed Pd seeds on the support layer and the enhanced bonding between the Pd layer and the support layer resulting from the strong anchoring of the Pd seeds onto the support in the new activation step.

Influence of palladium particles impregnation on hydrogen behavior in meso-porous silicon

The composite materials based on porous silicon (PS) with palladium particles incorporated inside the pores were prepared by means of Pd electroless deposition and characterized by optical microscopy, scanning electron microscopy and FTIR spectroscopy. Adsorption and desorption of molecular hydrogen at 50 kPa and ambient temperature as well as chemical extraction of H2 during the reaction of initial PS and PS + Pd composites with water and base were studied. Reversible uptake of molecular H2, probably due to the formation of palladium hydride, was detected for PS + Pd composites, otherwise the initial PS was found to be inactive to the H2 under ambient conditions. The composites PS + Pd react with water much slower and release less H2 in compare with initial PS, probably due to partial pore blockage by Pd. However, the pretreatment of the composites in gaseous H2 increases the volume of H2 evolving in the reaction with H2O at ambient temperature.

Characterization of Electroless Deposition of Pd on HOPG Surface by AFM and SEM

not Available.