Thermal Reduction of Pd Molecular Cluster Precursors at Highly Ordered Pyrolytic Graphite Surfaces

Abstract

Highly ordered pyrolytic graphite (HOPG) surfaces were modified by the adsorption of Pd molecular precursors from solution. Two palladium-containing molecular precursors were studied, a mononuclear one and a trinuclear one, to compare their affinities and distributions at substrate surfaces. To obtain Pd nanoparticles, these neutral molecular precursors were reduced under a hydrogen atmosphere. Thermogravimetric analysis was carried out to establish the behavior of these precursors at various temperatures. Understanding the thermal stability of these compounds is very important to establish the appropriate conditions to form metallic Pd. The modified surface has been characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy; also, the reductive process was monitored by XPS. Remarkable differences were observed between the mononuclear and trinuclear compounds in terms of dispersion, particle size, and homogeneity. The preference of the trinuclear compound was to deposit at HOPG defects, in contrast to that of the mononuclear one, which was agglomeration on all surfaces. After the application of this technique, not only Pd nanoparticles but also Pd nanowires were obtained.

Nanostructural Formation of Pd-Co Bimetallic Complex on HOPG Surfaces: XPS and AFM Studies

“…Other samples examined by AFM and scanning electron microscopy (SEM) showed diameters ranging from 150 nm to 8.1 μm and the heights between 10 and 400 nm with a maximum frequency at 60 nm. Similar results were observed with palladium precursors [7,8]. The interaction between precursor-solvent-substrate and the evaporation process play an important role in the rings structure formation [8,9].…”

Surface analysis and electrochemical characterization of palladium–cobalt nanoring formation from molecular precursor, [Et3NH]2[CoPd2(μ‐4‐I‐3,5‐Me2pz)4Cl4], on highly ordered pyrolytic graphite

“…Díaz‐Ayala et al . presented similar nanostructures formation for the deposition of Pd‐pyrazolate complex on HOPG surfaces . These nanostructures on HOPG exhibited a tube‐like shape in microsize to nanosize regime of diameter and height.…”

“…Díaz‐Ayala et al . presented the self‐formation of Pd nanoparticles, nanowires, nanorings and bonfire‐like structures from the deposition of the molecular precursor in dichloromethane solution on HOPG surface . They found the Pd nanowires on the HOPG edge steps and the rings at the basal plane.…”

Synthesis of Pd Nanoparticles in La-doped Mesoporous Titania with Polycrystalline Framework

“…Palladium only has one chemical state in Pd(P)/LaMT (figure 4a), which indicates the reduction was complete. The dispersion and the particles size of Pd 0 will affect the Pd 3d 5/2 binding energy values greatly [20]. The Pd 0 3d 5/2 binding energy of Pd(P)/LaMT is 335.8 eV, 0.2 eV higher than that of Pd(H)/LaMT, which may be due to higher dispersion and smaller size of Pd nanoparticles.…”