Electrocatalytic hydrogenation activity of palladium and rhodium microparticles dispersed in alkylammonium- and pyridinium- substituted polypyrrole films

Abstract

Zerovalent palladium and rhodium catalysts have been dispersed in conducting anion-exchange polymers coated on carbon-felt electrodes by oxidative electropolymerization of pyrrole monomers containing alkylammonium or pyridinium groups. Incorporation of metal catalysts in polymeric films was effected either by impregnation of PdCIz-or RhCIi-complexes followed by an electroreductive precipitation to PdO or Rho (method A), or by electroreduction of polymer-coated electrodes immersed in K,PdCI, or Na,RhCI, aqueous solutions (method B). A study of the electrocatalytic activity in hydrogenation of isophorone of various electrodes differing in loading level and incorporation method of metal catalysts was performed. Their activity increased with increasing amounts of metal in the polymer. The most efficient electrodes were obtained by incorporation (method A) of rhodium in poly(pyrro1e-alkylammonium) films. Scanning electron microscopy (SEM) showed a dispersion of metal particles from 100-200 nm (method A) up to 2000 nm (method B) on the polymer surface and a large accumulation of metal at the carbon substrate/polymer interface. These results were confirmed by Auger electron spectroscopy (AES) depth profile analysis, which also showed that metal catalyst is dispersed throughout the polymer overlayer. Differences in catalytic activities of method A and method B cathodes could be due to a difference in metal particle sizes.

Electrocatalytic Hydrogen Evolution from Molybdenum Sulfide–Polymer Composite Films on Carbon Electrodes

“…of 2.5 nm. After modification of the ITO surface with a poly(pyrrolealkylammonium) film, the topography appeared granular, typical of an electrodeposited poly-1 film, 28 and the r.m.s. value increased significantly to 10 nm (Figure 4B).…”

A Polyaniline-Based Selective Hydrogen Sensor

“…Generally, these efforts have been directed at the development of electrocatalytic electrodes for use in solution. Garnier has reported the incorporation of both platinum and silver microparticles into poly(3-methylthiophene) [5], while Moutet has described the incorporation of palladium and rhodium into N-substituted polypyrrole films [6]. Polyaniline has also been used as a matrix for the incorporation of palladium and platinum microparticles [7,8].…”

Metallic‐Based Nanocomposites of Conductive Polymers

“…Thus, starting with the early works of Tourillon and Garnier [88] and Chandler and Pletcher [89], interest in this area has continuously grown and has resulted in a large number of experimental studies. The electrodeposition of various metals of practical interest, such as Pt [51,79,, Au [20,[142][143][144][145][146][147], Pd [148][149][150][151][152][153][154][155][156][157][158], Ag [159][160][161][162][163], Cu , Ni [159,[190][191][192][193], Pb [89,138,159] etc. and also of Pt-based bimetallic systems [95,102,103,111,112,126,135] has been extensively studied (Table 7.3).…”

“…This has been found to occur for the deposition of Pt in PPY [129,132], PANI [109], and PTHI [88], of Pd in PPY [149] and PANI [10], and of Cu in PPY [168]. If, however, sulfonated PPY is involved in the metal reduction of cationic species (Cu 2þ ) (instead of pristine PPY), a more uniform distribution of the metal phase inside the PPY-PSS layer is found due to the doping role that the metal cations take in this situation [168].…”