Electrochemical approaches to design materials for potential sensing and energy related applications

Extended conference abstrac

Electrochemical approaches in synthesis of high surface area materials

It is the aim of our work to carry out fundamental studies on designing and synthesizing high surface area functionalized foam and ordered structures for their potential sensing and energy related applications. We combine electrochemical synthesis with structural studies on different length scales including transmission electron microscopy. Templates are directly grown by electrodeposition, either by hydrogen bubble formation or by utilizing of ordered structures formed by anodic electrochemical oxidation. [1-3] We employed an elegant approach to obtain open, foam deposits of Ni and Ni alloys, by using electrodeposition at high current densities, to promote hydrogen evolution and bubble templating (cf. Fig.1). [1] In the next step, the high surface area of such materials was funtionalized by Pd utilizing galvanic displacement reaction. Electrochemical testing of the obtained open foam deposits shows promissing catalytical activity for hydrogen evolution in alkaline environments, as well as methanol and ethanol oxidation. In the case of fabrication of nanodendritic Ag simultaneously grown with porous anodic aluminium oxide we accomplished well anchored dendritic Ag nanostructures [2] of long-term stability [3]. 1. L. D. Rafailović, C. Gammer, C. Rentenberger, T. Trišović, C. Kleber, H. P. Karnthaler, Nano Energy, 2 (2012) 523 https://doi.org/10.1016/j.nanoen.2012.12.004 2. L.D. Rafailovic, C. Gammer, C. Rentenberger, T. Trisovic, C. Kleber, H.P. Karnthaler, Adv. Mater. 27 (2015) 6438 https://doi.org/10.1002/adma.201502451 3. L.D. Rafailovic, C. Gammer, J. Srajer, T. Trisovic, J. Rahel, H.P. Karnthaler; RSC Adv., 6 (2016) 33348, https://doi.org/10.1039/c5ra26632

Surface enhanced Raman scattering of dendritic Ag nanostructures grown with anodic aluminium oxide

We present the application of newly developed Ag nanodendrites (Ag-ND) grown together with anodic aluminium oxide for surface-enhanced Raman scattering (SERS). The Ag-ND yield very pronounced SERS using a self-assembled monolayer (SAM). This is confirmed by simulations showing hot spots in the electromagnetic field at the surfaces of the Ag-ND. SERS measurements reusing Ag-ND demonstrate its long-term stability even after one year

Enhanced oxygen evolution and reduction reactions of porous ternary NiCoFe foam electrodes prepared by dynamic hydrogen template deposition

Electrodeposition at high current densities provides excellent means for the production of deposits with a high surface area. Porous deposits attract great interest due to their wide range of possible applications in electrocatalysis. In addition, an advanced porous electrode should have both, micro and nanoscaled features. We report the synthesis of a multiscale open porous foam of NiCoFe and its excellent electrocatalytic performance. At a current density of 1 A cm−2 a 3D dendritic structure with open pores is obtained with pore walls having a morphology that consists of ‘cauliflower-like’ particles containing open multiscaled dendritic structures. Cyclic voltammograms of a smooth NiCoFe electrode are compared with those of the achieved nanodendritic NiCoFe foam electrode. The catalytic activity of the NiCoFe foam is strongly enhanced for both, the cathodic reduction of oxygen and the anodic evolution of oxygen and shows a good reversibility. Therefore the presented new material is promising as bifunctional catalyst in electrochemical energy conversion and storage devices

Microstructure and mechanical properties of disperse Ni-Co alloys electrodeposited on Cu substrates

The nickel and cobalt disperse alloy deposits of five different compositions were obtained by electrodeposition on Cu substrates in the galvanostatic regime from an ammonium sulfate-chloride solution. The effect of cathodic current density and Ni2+/Co2+ ions concentration ratio in the electrolyte on the composition, microstructure, morphology and mechanical properties of Ni-Co alloys were investigated. Conditions for formation of nanostrustured disperse deposits and surface roughness was determined by 3D SEM reconstruction of the specimen surface. It was established that formation of the disperse deposits with highly developed structures is favored from bath with equal Ni2+/Co2+ ions concentration ratio in the electrolyte. Cathodic polarization diagrams determined for all investigated alloys have shown shift of the cathodic potential for alloy deposition to the more negative values with increasing Ni2+/Co2+ ions concentration ratio in the electrolyte. An increase of in the cobalt content in the alloy was observed with decreasing the current density and increasing of the Co2+ ions concentration ratio in the bath. X-ray analyses of nanocrystalline Ni-Co deposits show formation of a single phase face-centered cubic (FCC), a single phase hexagonal-close packed (HCP) and mixture of FCC solid solutions and HCP phase depending on the current density applied and electrolyte composition. The increase of HCP phase content in the nanocrystalline deposits appears as a result of both, the increase in Co2+ ions concentration in the bath and decrease of deposition current density. The mechanical properties of nanocrystalline deposits have shown increase of the hardness with increasing Ni content in the alloy. The cross-section of the samples electrodeposited on Cu substrates from electrolytes with equal ion metal concentration at lower current density values revealed the beginning of a dendrite structure formation. © 2009 Elsevier B.V. All rights reserved

Atomic layer deposition by reaction of molecular oxygen with tetrakisdimethylamido-metal precursors

Tetrakisdimethylamido (TDMA) based precursors are commonly used to deposit metal oxides such as TiO2, ZrO2, and HfO2 by means of chemical vapor deposition and atomic layer deposition (ALD). Both thermal and plasma enhanced ALD (PEALD) have been demonstrated with TDMA-metal precursors. While the reactions of TDMA-type precursors with water and oxygen plasma have been studied in the past, their reactivity with pure O2 has been overlooked. This paper reports on experimental evaluation of the reaction of molecular oxygen (O2) and several metal organic precursors based on TDMA ligands. The effect of O2 exposure duration and substrate temperature on deposition and film morphology is evaluated and compared to thermal reactions with H2O and PEALD with O2 plasma

Functionalizing Aluminum Oxide by Ag Dendrite Deposition at the Anode during Simultaneous Electrochemical Oxidation of Al

A novel synthesis strategy is presented for depositing metallic Ag at the anode during simultaneous electrochemical oxidation of Al. This unexpected result is achieved based on galvanic coupling. Metallic dendritic nanostructures well-anchored in a high surface area supporting matrix are envisioned to open up a new avenue of applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Study of the dendritic growth of Ni-Co alloys electrodeposited on Cu substrates

Ni-Co alloy deposits and their parent metals were formed on Cu substrates by electrolysis under different current densities applied in the galvanostatic regime. A quantitative scanning electron microscopy technique was employed to study the morphology and surface roughness of the obtained deposits. The structure of the deposits is governed by the nature of depositing ions and quantity of evolved hydrogen. The cauliflower morphology and the highest mean surface roughness values are the results of electrodeposition from the Ni containing bath. The structure of the Co deposits formed under the same conditions and determined by the formation of the hexagonal close-packed phase results in a more uniform grain size distribution and formation of smoother platelet deposits. The mean surface values of the parent metals are independent of the current density. The dendritic growth is a special case of a structure formed only in the Ni-Co alloy deposition at selected, high current densities of 220 and 400 mA cm-2. The dendrites obtained at a higher current density of 400 mA cm-2 have shown more developed structures with smaller dendrites that have more pronounced secondary branch and high order branches. © 2010 The Electrochemical Society