Studies on the electrocatalytic reduction of aliphatic aldehydes on palladium‐modified carbon paste electrodes

Abstract

Carbon paste electrodes modified either by mixing palladium powder to the electrode material or by electrodepositing Pd via cycling the potential between 0.4 and -0.7 V (versus SCE) exhibited stable electrocatalytic response for aliphatic aldehydes and aliphatic alcohols. The aldehydes ( e g , formaldehyde) could be reduced to the corresponding alcohols (e.g., methanol), and the alcohols ( e g , methanol) could be oxidized to the corresponding aldehydes (e.g., formaldehyde) by direct current voltammetry (DCV). The electrocatalytic effect was attributed to the electrogenerated metallic palladium at the electrode surface. The cathodic current peak, the height of which was proportional to the aldehyde concentration, had negative values; it was ascribed to a desorption of the product of the electrode reaction from the surface of the electrode. This peak was used for quantitative analytical purposes.

Electrocatalytic amperometric detection of hydroxylamine with a palladium‐modified carbon paste electrode

“…The increase of the FIA response with slow flow rate is easily understood. However, the decrease with faster rates indicates that probably the chemical reaction step in the whole electrocatalytic process is rate-determining, i.e., it is so slow that there is not enough time to produce sufficient electroactive reactant, which is probably some complex between hydroxylamine and Pd(O)& at the electrode surface [12]. A similar phenomenon was also observed with electrodes modified with Cu or RuOz for the oxidation of aliphatic alcohols and carbohydrates .…”

“…3). Therefore, P depends on Po, which means that the product of the reduction causing Po (i.e., Pd(O)&,) must be involved in the electrochemical reaction which produces P, just as was found for the oxidation of aliphatic alcohols at the Pd-CPEs [12].…”

“…The scan rate (5 to 200mV -s-l) is of no importance for the electrocatalytic activity of Pd(0))tu, on the electrode surface, because after several cyclic scans a stable current response Po can be observed. Po was thoroughly studied in our previous work [12] and was assigned to the reduction of Pd(I1) which had been formed at positive potentials. The product was found to be electrogenerated palladium(O), Pd(O)&,, which was responsible for the electrocatalytic activity of the electrode.…”

“…To our knowledge, however, no report concerning electrocatalytic and amperometric detection ad hydroxylamine has been made until now. In this laboratory, an extensive study concerning the electrocatalytic behavior of the palladiummodified carbon paste electrodes (Pd-CPESs) towards the reduction of aliphatic aldehydes and the oxidation of aliphatic alcohols was made [12]. Further studies showed that these electrodes can also respond to hydroxylamine.…”

Generation of OH radicals at palladium oxide nanoparticle modified electrodes, and scavenging by fluorescent probes and antioxidants

“…Palladium and other platinum-group metal islands at the nanometer to micrometer range have been produced on different substrates and used as catalysts for oxygen reduction reaction, which is one of the most extensively investigated processes in electrochemistry mainly for fuel cell research [4][5][6]. Palladium nanoparticles have also been used in electroanalysis as electrocatalyst in modified electrodes for the detection of H 2 O 2 , O 2 , NO, glucose and hydrazines [7][8][9][10][11][12][13][14].…”