Electrochemically activated-iron oxide nanosheet arrays on carbon fiber cloth as a three-dimensional self-supported electrode for efficient water oxidation

The development of non-precious, earth-abundant and efficient water oxidation catalysts is very important for water splitting systems associated with the conversion and storage of renewable energy. Here, we report a facile method to fabricate amorphous iron oxide nanosheet arrays on carbon fiber cloth (CFC) as a three-dimensional (3D) self-supported electrode for efficient water oxidation. FeSOy nanosheets with a lateral size of 400 nm and a thickness of 20 nm were first grown on a CFC substrate by a hydrothermal method, and were then converted to FeOx nanosheets without an obvious change in the morphology and size through a rapid and in situ electrochemical oxidation desulfurization process. After the electrochemical activation process, the 3D self-supported electrodes exhibited superior OER activity to previously reported iron oxide films, and were even comparable to some state-of-the-art OER catalysts such as cobalt oxides. Furthermore, the 3D self-supported electrodes showed excellent stability toward the OER process even at a high current density. Surprisingly, the activity of the 3D self-supported electrode was enhanced significantly after the long-term OER process. In addition, the direct growth of the active catalysts on the CFC substrate can avoid the use of other conductive agents and binders, which ensures good electrical connection and improves the electrical conductivity of the electrode. The superior activity and long-term stability as well as the facile fabrication process demonstrated that the 3D self-supported electrode has promising application in large-scale water splitting.