Multi-Walled Carbon Nanotubes Supported Pd(II) Complexes: A Supramolecular Approach towards Single-Ion Oxygen Reduction Reaction Catalysts

Abstract

Lowering the platinum group metal content of oxygen reduction reaction catalysts is among the most prevalent research focuses in the field. This target is herein approached through supported Pd(II) complexes. Starting from a commercial macrocycle, a new ligand is synthesized, its solution behavior and binding properties briefly explored (potentiometry, UV-Vis) and then used to prepare a new catalyst. A supramolecular approach is used in order to obtain homogeneous decoration of carbon nanotubes surfaces, fostering novel possibilities to access single-ion active sites. The novel catalyst is characterized through X-ray photoelectron spectroscopy and scanning transmission electron microscopy and its promising oxygen reduction reaction performance is evaluated via rotating ring-disk electrode and rotating disk electrode in half-cell studies.

Predictive Removal of Interfacial Defect-Induced Trap States between Titanium Dioxide Nanoparticles via Sub-Monolayer Zirconium Coating

“…High-resolution transmission electron microscopy images were acquired using a double aberration-corrected 200 keV JEOL 2200FS (scanning)/transmission electron microscope ((S)TEM) with a field emission gun equipped with a Thermo Scientific Noran 7 energy-dispersive X-ray (EDX) detection system. Sample preparation for TEM analysis was done by dusting sample powder following a literature procedure 38 onto holey carbon films supported by 300 mesh TEM Cu grids (Agar Scientific, S147-3) thermally pre-treated. 39 XPS measurements were taken using a Kratos Axis Supra using a monochromated Al-ray anode (1486.69 eV) and fitted with a charge neutralizer.…”

Noncovalent Assembly and Catalytic Activity of Hybrid Materials Based on Pd Complexes Adsorbed on Multiwalled Carbon Nanotubes, Graphene, and Graphene Nanoplatelets

“…Then, the adsorption of PdCl 4 2– on these hybrids was carried out until a 1:1 ligand/Pd molar ratio was obtained, thus providing the catalysts G-L1-Pd and MWCNT-L2-Pd in which most of the Pd­(II) was adsorbed via complexation by the common macrocyclic polyamine function of the corresponding ligand. The adsorption of L1 and L2 on the carbon substrates was ensured by the π–π stacking interaction of the 6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxo-pyrimidine ligand moieties (two in L1, one in L2) with the graphene surfaces of MWCNTs and G. The use of this adhesive pyrimidine residue was initially introduced by some of us for the functionalization of activated carbon (AC) aimed at the removal of chromate anions from aqueous solutions and was later extended to the generation of new materials for further remediation purposes (cation and anion sequestration) − as well as for applications in fuel cells (oxygen reduction reactions), − hydrogenation processes, and the photochemical generation of hydrogen …”

cis-[6-(Pyridin-2-yl)-1,3,5-triazine-2,4-diamine](dichloride) Palladium(II)-Based Electrolyte Membrane Reactors for Partial Oxidation Methane to Methanol

“… 14 − 18 In this sense, electrocatalysts based on macrocyclic, linear, and multidentate ligands N-coordinated to transition metals have been explored in fuel cells. 19 − 24 …”

“…Recently, palladium has been reported as a promising metal for partial oxidation of methane due to the formation of a thin layer of PdO on the catalytic surface, which displays an affinity with methane and the oxy-hydroxide species at a low overpotential that can activate the water, an important step for hydrocarbon oxidation. − However, the price of Pd metal has increased over the last few years. Meanwhile, the metal–ligand complex has gained increasing attention as electrocatalysts due to the lower proportion of metals; these materials have a large specific surface area and high porosity and are readily available. − In this sense, electrocatalysts based on macrocyclic, linear, and multidentate ligands N-coordinated to transition metals have been explored in fuel cells. − …”