Glycerol oxidation at Pd nanocatalysts obtained through spontaneous metal deposition on carbon substrates
Roman Ivanov, A. Nakova, V. Tsakova
Abstract
Spontaneous deposition of Pd is carried out on five different carbon-based screen-printed electrodes (SPEs) in the absence of solute reductant species in the Pd ions solution. Pd nanoparticles (NPs) with mean sizes ranging between 11.2 and 17.9 nm and homogeneous distribution are obtained on the carbon supports. The NPs mean size and amount of available metal are found to depend on the type of the carbon SPE, i.e. carbon (C110), mesoporous carbon (MC), carbon nanofibers (CNF), single- or multi-walled carbon nanotubes (SWCNT or CNT). Overlapping and agglomerating particles are found only in the SWCNT case whereas for all other electrodes the individual NPs are well isolated. Glycerol oxidation is studied at the five types of Pd nanocatalysts and data for the mass activity are obtained for glycerol and KOH concentrations used in fuel cells applications. The data for the mass activity correlate with the electroactive surface area (EASA) of the metallic particles for three of the electrodes (C110, MC and CNF) whereas Pd NPs supported by multi walled CNTs show a very high mass activity not to be associated with increased EASA alone. In separate experiments the applicability of the Pd-carbon-based SPEs is studied in view of electroanalytical detection of glycerol. A stable electroanalytical response is found for the MC, CNT and CNF SPEs. The concentration dependence of the glycerol oxidation peak current is modeled by a Langmuir type function that allows for detection of glycerol in the 0.2 to 15 mmol/l concentration range. The ease of preparation of the Pd nanocatalysts and the use of disposable SPEs present a good prospect for practical applications.