There is a great interest in electrochemical water splitting for the efficient utilization of sustainable energy. As an alternative to high-priced materials, carbon offers a considerable potential. However, carbon is limited as an electrode material for oxygen evolution reaction (OER) due to its thermodynamic instability against electrochemical oxidation. In this study, we investigated the electrochemical degradation of multiwall carbon nanotubes (MWCNTs) under the acidic OER environment. Electrochemical oxidation of MWCNTs induces structural changes and the formation of oxygen-containing functional groups on the carbon surface. We carried out electrochemical, microstructural and spectroscopic analysis in order to investigate the degradation of MWCNTs. By changing of the electrochemical properties of MWCNTs during the oxidation process, carbon is initially activated and then can be kinetically stabilized in the OER condition.