Electrodeposited 3D Nanomesh Electrodes: Combined High Surface Area, High Porosity and Structural Integrity and Regularity

Abstract

We present a nanomesh material that is widely applicable in a variety of sustainable-applications requiring high surface area electrodes such as batteries, electrocatalytic convertors, fuel cells and hydrogen production. The nanomesh material is a three-dimensional nanowire (metal) grid structure with highly regular internal dimensions. The hexagonally organized vertical nanowires are horizontally interconnected to its three neighboring nanowires. As a result, it combines high porosity with an unprecedented surface-to-volume ratio. For each micrometer thickness, there is a 26-fold increase of available surface area. To visualize this: when filling a volume of a small can of soda, it would remain 75% empty while containing a surface area equal to the size of a football field. On top of that, the internal and external dimensions can be tuned to almost any specification, making it potentially compatible with a multitude of application requirements. The material can be quite easily manufactured through cheap anodization and electroplating processes. First, a mold is formed by anodization of aluminum foil as for the well-known Anodic Aluminum Oxide (AAO) process. The secret for the regular horizontal perforation at the nanoscale lays in the controlled doping of the aluminum metal with copper. The resulting 3D nanoporous structure acts as a mold in which a large variety of metal (compounds) can be electrodeposited. After consecutive chemical dissolution of the alumina template, a mechanically rigid nanomesh structure remains. The nanomesh can be detached from the substrate as a free-standing flexible nanomesh foil. We will show that a 3 micron thick nanomesh easily outperforms a 400 micron thick foam in surface area and electrochemical performance for hydrogen evolution reaction.