The high surface area per unit volume and large mass-transfer rates offered by three-dimensional porous electrodes have resulted in their use in a wide variety of electrochemical processes, including organic electrosynthesis, water electrolysis, water treatment, fuel cells, and redox flow batteries.^1-4 Many types of porous electrodes are commercially available, including carbon paper, graphite felt, reticulated vitreous carbon (RVC), metal mesh, and metal foam. Metal foam offers relatively high conductivity (1.5x10^-5 ohm m) but low surface area (<4x10⁴ m^-1),⁵ whereas carbon paper has one of the highest surface areas (up to 1.6x10⁵ m^-1) but lower conductivity (4.7x10^-5 ohm m).⁶

This presentation will describe the characteristics of a copper nanowire electrode (Fig. 1) that has 15 times more surface area (2.4x10⁶ m^­-1) and is 33 times more conductive (1.6x10^-6ohm m) than carbon paper. The improvement in surface area is due to the small diameter of the nanowires relative to carbon fibers in carbon paper, whereas the high conductivity is due to intrinsically higher conductivity of Cu, and the fact that the metal nanowires can be sintered together, forming highly conductive inter-nanowire contacts. The porosity of the nanowire electrode is 0.94, and its permeability was only 4 times lower than carbon paper. This presentation will report the electrochemical performance of the Cu nanowire electrode relative to carbon paper for the reduction of Cu ions in a flow-through geometry. The high-conductivity, high surface area, and high porosity that can be achieved with Cu nanowire electrodes creates new opportunities for improving the performance of electrochemical systems for energy storage, hydrogen production, water treatment and the production of fine chemicals.

References:

1. J. Newman, and W. Tiedemann, AIche J., 21, 25 (1975).

2. R. Alkire, and P.K. Ng, J. Electrochem. Soc., 124, 1220 (1977).

3. J.M. Friedrich, C. Ponce-De-Leon, G.W. Reade, and F.C. Walsh, J. Electroanal. Chem., 561, 203 (2004).

4. S. Porada, L. Weinstein, R. Dash, A. van der Wal, M. Bryjak, Y. Gogotsi, and P. M. Biesheuvel, ACS Appl. Mater. Interfaces, 4, 1194 (2012).

5. S. Langlois, and F. Coeuret, J. Appl. Electrochem., 19, 43 (1989).

6. S.C. Barton, Y. Sun, B. Chandra, S. White, and J. Hone, Electrochem. Solid-State Lett., 10, B96 (2007).

Figure. 1.(A) Image of a porous Cu nanowire electrode. (B) SEM image of the nanowires in the electrode.