Indirect (hydrogen-driven) electrodeposition of porous silver onto a palladium membrane
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ORIGINAL PAPER
Indirect (hydrogen-driven) electrodeposition of porous silver onto a palladium membrane Tinakorn Kanyanee 1,2,3 & Philip J. Fletcher 4 & Elena Madrid 1 & Frank Marken 1 Received: 5 March 2020 / Revised: 2 April 2020 / Accepted: 2 April 2020 # The Author(s) 2020
Abstract Hydrogen permeation through a pure palladium film (25 μm thickness, optically dense) is employed to trigger electron transfer (hydrogen-driven) reactions at the external palladium | aqueous electrolyte interface of a two-compartment electrochemical cell. Two systems are investigated to demonstrate feasibility for (i) indirect hydrogen-mediated silver electrodeposition with externally applied potential and (ii) indirect hydrogen-mediated silver electrodeposition driven by external formic acid decomposition. In both cases, porous metal deposits form as observed by optical and electron microscopies. Processes are self-limited as metal deposition blocks the palladium surface and thereby slows down further hydrogen permeation. The proposed methods could be employed for a wider range of metals, and they could provide an alternative (non-electrochemical or indirect) procedure for metal removal or metal recovery processes or for indirect metal sensing. Keywords Indirect electrodeposition . Reduction by hydrogen . Palladium membrane . Dendritic silver . Porous silver . Metal recovery
Introduction Metal electrodeposition processes are used primarily in metal and metal alloy coating [1, 2] and in metal recovery from wastes [3, 4]. Metal electrodeposition and stripping processes are also an integral part of electroanalytical procedures to determine trace metal in water or in the environment [5]. Electrodeposition is dependent on the applied potential, on the substrate, and on the type of metal that is formed. Electrodeposition is also a key technology in the fabrication of many microelectronic, optoelectronic, and microsystem
* Tinakorn Kanyanee [email protected] * Frank Marken [email protected] 1
Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
2
Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
3
Center of Excellence in Materials Science and Technology, Chiang Mai University, Chiang Mai 50200, Thailand
4
Materials and Chemical Characterisation Facility (MC2), University of Bath, Claverton Down, Bath BA2 7AY, UK
devices [6, 7]. Electrodeposition can be cost-effective and useful for conformal coating of complex shapes and objects [8]. An interesting recent development is electrodeposition of metals from non-aqueous or non-traditional solution environments [9]. Electroless plating can be performed by adding chemical-reducing agents directly into the metal ion solution to be deposited, for example, to prepare palladium-metal and alloy films [10, 11]. Complex geometries can be electrolessly metal-coated [12]. Here, rather than directly adding a reducing agent, hydrogen permeating through a palladium film is used to indirectly drive metal deposition proc
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