Green synthesis of a carbon-rich layer on the surface of SiC at room temperature by anodic etching in dilute hydrofluoric acid/ethylene glycol solution

Carbide-derived carbons (CDCs) are a growing class of nanostructured carbon materials with properties that are desirable for many applications, ranging from electrical energy to gas storage. However, the synthesis of CDCs often requires high temperatures and/or pressures, as well as toxic chemicals. In this report, we demonstrate environmentally friendly synthesis of a carbon-rich layer on the surface of SiC by anodic etching at room temperature in a highly diluted solution of hydrofluoric acid in ethylene glycol. In our opinion, the carbon-rich layer was formed thanks to the fact that we have used the etching conditions in which the rate of removal of carbon from SiC has become significantly lower compared with the silicon removal rate. More specifically, we have created an environment for SiC anodic etching where there is little water. In such conditions, silicon is still being removed from SiC, thanks to the direct dissolution, whereas the carbon removal rate is significantly reduced, due to the fact that carbon can be lost only by oxidation, but there is not enough water to oxidize carbon as in solutions with plenty of water. Thus, a carbon-rich layer is created on the etched SiC surface.