Mkhulu K. Mathe

Electrodeposition of Multilayered Bimetallic Nanoclusters of Ruthenium and Platinum via Surface-Limited Redox−Replacement Reactions for Electrocatalytic Applications

An electrochemical synthesis of multilayered bimetallic Ru|Pt nanoclusters, supported on glassy carbon, is reported for the first time. The novel nanoclusters were synthesized via surface-limited redox-replacement reactions involving sacrificial Cu, deposited prior to the formation of each individual noble metal layer, in a sequential fashion. It has been shown that the Cu adlayers control the morphology and electrochemical properties of the resultant nanostructures. Sequentially deposited Ru|Pt nanoclusters exhibited superior electrocatalytic activity (when compared to equivalent monometallic Pt and an alloy-type codeposited Pt-Ru nanostructures) with respect to methanol electrooxidation in an acidic medium. Moreover, it has been established that the electrochemical process taking place at the Ru|Pt nanoclusters followed the bifunctional mechanism. Electrokinetic studies of the oxygen reduction reaction (ORR) were also performed. Analysis of hydrodynamic linear sweep voltammetric experiments, performed at various flow rates on oxygen-saturated acidic medium, revealed that the Pt and Ru|Pt nanoclusters exhibited direct four- and two-electron ORR pathways, respectively. A specially designed electrochemical flow-cell was used for automated sequential electrodeposition of the multilayered nanoclusters of predefined composition and electrochemical and electrocatalytic investigations.

Formation of HgSe Thin Films Using Electrochemical Atomic Layer Epitaxy

The growth of HgSe using electrochemical atomic-layer epitaxy (EC-ALE) is reported. EC-ALE is the electrochemical analog of ALE, where electrochemical surface-limited reactions referred to as underpotential deposits, generally result in the formation of an atomic layer of an element, under controlled potential. HgSe thin films were formed on gold substrates using two reactant solutions: a solution of Hg 2 + complexed with ethylenediaminetetraacetic acid and a HSeO - 3 ion solution. X-ray diffraction analysis showed a zinc blende structure for the deposits, with a strong (111) preferred texture, and an average grain size of 425Δ. Electron probe microscope analysis showed near-stoichiometric deposits. Fourier transform infrared spectroscopy reflection absorption measurements suggest two bandgaps: 0.42 and 0.88 eV.

Automated electrodeposition of bimetallic noble-metal nanoclusters via redox-replacement reactions for electrocatalysis

Online content of final published article downlowadable at cost at following link (DOI)http://dx.doi.org/10.1149/1.3246602