Electrochemical atomic layer deposition (E-ALD) of Pt and PtRu nanofilms
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Electrochemical atomic layer deposition (E-ALD) has been developed in this research group to grow monometallic and bimetallic nanofilms. E-ALD is an electrochemical analog of atomic layer epitaxy (ALE) and atomic layer deposition (ALD), all of which are based on growth of material an atomic layer at a time. Under potential deposition (UPD) is a thermodynamic process, where one element forms an atomic layer on to the other. A less noble metal (Sacrificial metal) is deposited at UPD and is then exchanged with more noble metal at open circuit potential (OCP). This process is referred to as surface limited redox replacement reaction (SLRR). E-ALD promotes two-dimensional growth, resulting in better control of composition and structure than conventional electrodeposition method. The present study investigates E-ALD using UPD and SLRR cycles to form metal nanofilms on Au on glass substrates. Pb and Cu were explored as the sacrificial metal. Pt, Ru, PtRu and Ru modified Pt nanofilms were deposited using a labview program. Pt and Pt based alloys are of interest as a electrode materials in fuel cells. Electrodeposits were formed in an automated flow cell system consisting of pumps, valve, electrochemical cell and a potentiostat; all controlled using a labview program. The nanofilms were deposited and characterized by cyclic voltammetry in sulfuric acid. The catalytic activity of the nanofilms was studied by CO adsorption and electrooxidation. Current and open circuit potentials were monitored simultaneously as a function of time. The atomic proportions were determined from electron probe microanalysis (EPMA).