Oxygen plasma functionalization of hexacyanocobaltates for high-capacity supercapacitor electrodes

Supercapacitors have attracted much attention because of their unique advantages. Electrode materials, as one of the most important parts, have already been the focus of research. A great effort has been made to address the drawback of low capacity, for example, annealing, forming compound and doping. However, these methods have not brought significant improvement of capacity. Here, we develop a facile method for enhancing the specific capacity of cobalt hexacyanocobalte using oxygen plasma etching. The specific capacity of the engraved sample increased by 62.15% (from 214.0C g(-1) to 347.0C g(-1) at a current density of 1 A g(-1)). The excellent capacitive performance is attributed to the synergistic effect of increasing K+ diffusion velocity, exposing more active sites and promoting hydrophilicity. This method may be extended to dramatically improve the specific capacity of Prussian blue, its analogs and even other metal-organic frameworks materials.