Graphite Felt Modified by Atomic Layer Deposition with TiO2 Nanocoating Exhibits Super-Hydrophilicity, Low Charge-Transform Resistance, and High Electrochemical Activity

Graphite felt (GF) is a multi-functional material and is widely used as electrodes of electrochemical devices for energy and environmental applications. However, due to the inherent hydrophobicity of graphite felt, it must be hydrophilically pretreated to obtain good electrochemical activity. Metal oxides coating is one of the feasible methods to modify the surface of GF, and in order to ensure that the metal oxides have a better conductivity for obtaining higher electrochemical activity, a subsequent H2 heat-treatment process is usually adopted. In this study, atomic layer deposition (ALD) is used to deposit TiO2 nanocoating on graphite felt (GF) for surface modification without any H2 thermal post-treatment. The results show that the ALD-TiO2-modified GF (ALD-TiO2/GF) owns excellent hydrophilicity. Moreover, the ALD-TiO2/GF exhibits excellent electrochemical properties of low equivalent series resistance (Rs), low charge-transfer resistance (Rct), and high electrochemical activity. It demonstrates that ALD is an applicable technique for modifying the GF surface. In addition, it can be reasonably imagined that not only TiO2 film can effectively modify the GF surface, but also other metal oxides grown by ALD with nanoscale-thickness can also obtain the same benefits. We anticipate this work to be a starting point for modifying GF surface by using ALD with metal oxides nanocoating.