Due to the significance of Ascorbic Acid (AA) fuel cells in biological systems and energy storage applications, the development of efficient electrochemical strategies is needed. In the present work, the electrochemical oxidation of AA is performed with Multiwalled Carbon Nanotubes (MWCNTs) anodes which have controlled oxygen content, modulated by acid reflux treatment. Furthermore, a total oxygen content increase of just 2% on MWCNTs surface was sufficient to achieve an enhanced AA electrocatalytic oxidation. The oxygen content was notoriously lower than other nanocarbon materials like unzipped carbon nanotubes and reduced graphene oxide which normally are considered as optimal materials. The surface chemical composition on MWCNTs was analyzed by XPS. The anodes were prepared as carbon film electrodes (CFE) by dropping cast procedure on GC surface (current collector). Cyclic voltammetry was used to evaluate the electrochemical responses of these electrode materials varying the concentration of AA (10, 50 and 100 mM). At a fixed concentration, the electrochemical responses show an increase in current and a shift of peak potential that facilitate oxidation as the acid treatment time increases. It was found that the COO- groups are responsible for the enhanced catalytic behavior of these modified MWCNTs. The simple change of functional groups by the same acid treatment procedure at different times has a notorious effect on AA oxidation. These findings provide straightforward selection criteria for anodes devoted to AA fuel cell design. Also, it is demonstrated that MWCNTs can still provide new alternatives for enhanced electrocatalytic processes. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.