Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
1] Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA [2] Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Sci Rep. 2014 Nov 14;4:7056. doi: 10.1038/srep07056.
Understanding over-limiting current (faster than diffusion) is a long-standing challenge in electrochemistry with applications in desalination and energy storage. Known mechanisms involve either chemical or hydrodynamic instabilities in unconfined electrolytes. Here, it is shown that over-limiting current can be sustained by surface conduction in nanopores, without any such instabilities, and used to control dendritic growth during electrodeposition. Copper electrodeposits are grown in anodized aluminum oxide membranes with polyelectrolyte coatings to modify the surface charge. At low currents, uniform electroplating occurs, unaffected by surface modification due to thin electric double layers, but the morphology changes dramatically above the limiting current. With negative surface charge, growth is enhanced along the nanopore surfaces, forming surface dendrites and nanotubes behind a deionization shock. With positive surface charge, dendrites avoid the surfaces and are either guided along the nanopore centers or blocked from penetrating the membrane.
理解超扩散电流（比扩散更快）是电化学中的一个长期挑战，在脱盐和储能方面有应用。已知的机制涉及无约束电解质中的化学或流体动力不稳定性。在这里，研究表明，超扩散电流可以通过纳米孔中的表面传导来维持，而不会产生任何这种不稳定性，并可用于控制电沉积过程中的枝晶生长。通过在带有聚电解质涂层的阳极氧化铝膜中生长铜沉积物来修饰表面电荷，从而实现铜的电沉积。在低电流下，由于双电层较薄，均匀电镀不受表面修饰的影响，但在极限电流以上，形态发生了显著变化。带负电荷时，生长沿纳米孔表面增强，在去离子冲击波后面形成表面枝晶和纳米管。带正电荷时，枝晶避开表面，要么沿纳米孔中心引导，要么阻止其穿透膜。
