Controlling Interfacial Ion-Transport Kinetics Using Polyelectrolyte Membranes for Additive- and Effluent-free, High-Performance Electrodeposition

Abstract

The development of high-performance, environmentally friendly electrodeposition processes is critical for emerging coating technologies because current technologies use highly complex baths containing metal salts, supporting electrolytes, and various kinds of organic additives, which are problematic from both environmental and cost perspectives. Here, we show that a 200 μm-thin polyelectrolyte membrane sandwiched between electrodes effectively concentrates metal ions through interfacial penetration, which increases the conductance between the electrodes to 0.30 S and realizes solid-state electrodeposition that produces no mist, sludge, or even waste effluent. Both, experimental results and theoretical calculations, reveal that electrodeposition is controlled by ion penetration at the solution/polyelectrolyte interface, providing an intrinsically different ion-transport mechanism to that of conventional diffusion-controlled electrodeposition. The setup, which includes 0.50 mol L −1 copper sulfate and no additives, delivers a maximum current density of 300 mA cm −2 , which is nearly fivefold higher than that of a current commercial plating bath containing organic additives.

Interfacial analysis of the ion-transport process controlling the steady-state current in a two-phase electrodeposition system using polyelectrolyte membranes

“…Our previous study on setup A demonstrated that at constant voltage electrodeposition, the copper ions penetrated the solid, waterswollen polyelectrolyte membrane from the electrolyte solution, diffused through the membrane via an ion exchange reaction, and were finally reduced on the cathode surface. 26 Theoretical modelling and our experimental results revealed that ion penetration from the electrolyte solution into the polyelectrolyte membrane is the rate-determining step at the applied voltage up to 1.0 V using a 200 μm-thick membrane. 26 During constantvoltage electrodeposition, the current density decreases in the early stage of electrodeposition because of the decrease in the concentration of copper ions in the polyelectrolyte membrane, after which the current density stabilizes when the system reaches the steady state because of the balance between the deposition and penetration rates (Fig.…”

“…26 Theoretical modelling and our experimental results revealed that ion penetration from the electrolyte solution into the polyelectrolyte membrane is the rate-determining step at the applied voltage up to 1.0 V using a 200 μm-thick membrane. 26 During constantvoltage electrodeposition, the current density decreases in the early stage of electrodeposition because of the decrease in the concentration of copper ions in the polyelectrolyte membrane, after which the current density stabilizes when the system reaches the steady state because of the balance between the deposition and penetration rates (Fig. 2).…”

“…variable in eqn (4). 26 Therefore, the value of C PE can be estimated from the initial current (the current observed at t = 0 for constant-voltage electrodeposition, where t is the deposition time) using eqn (4). In fact, C PE is almost constant at 0.032-0.038 cm −1 for the range of distances (d soln ) of 0-1000 μm between the anode and polyelectrolyte membrane (Table 1).…”

“…[22][23][24][25] Recently, we reported a novel method for metal electrodeposition using polyelectrolyte membranes attached to a cathode substrate (solid electrodeposition, SED). 26 SED, which enables the deposition of metals directly on the cathode surface from metal ions in solid polyelectrolyte membranes, has desirable advantages, including a higher deposition rate, site selectivity, and deposition using an electrolyte solution with a lower concentration without additives. Owing to the utilization of solid polyelectrolyte membranes as ion transport media during the electrodeposition process, the system produces no mist, sludge, or waste effluent.…”

“…In addition, the steady-state current density of the system was determined by maintaining a strict balance between the voltage-dependent deposition rate and concentration-dependent penetration rate of the copper ions. 26 Herein, we describe a related system based on polyelectrolyte membranes that are sandwiched between the cathode and electrolyte solution. In this system, ion penetration is more efficient than that in the previous system in which the copper mesh anode came into contact with the membrane (Fig.…”