Enhanced surface properties and electrochemical performance of carbon-based screen-printed electrodes via hydrogen peroxide activation

• Different screen-printed carbon surfaces were electrochemically activated with H 2 O 2 • Increase in edge-type defects and vacancy defects on the activated carbon surfaces. • The C sp 3 / sp 2 ratio increased for all the activated carbonaceous electrodes. • Sheet resistance and Rct decreased for all the activated carbon surfaces. • ORR and OER were inhibited in the presence of NH 3 (aq) for the activated surfaces. Electrochemical activation of carbon inks from screen-printed electrodes is a key step in the development of high-performance electrochemical (bio)sensors. In this work, several carbon-based screen-printed surfaces, including amorphous carbon, multi-walled carbon nanotubes, graphene, graphene oxide and mesoporous carbon inks have been electrochemically activated by cyclic voltammetry in the presence of H 2 O 2 and characterized by HRSEM, Raman spectroscopy, XPS, sheet resistance, cyclic voltammetry and EIS. The carbonaceous materials showed different surface chemistry and morphology after activation, arising from different features such as defects concentration, inter-defect distances, formation of holey material and changes in surface functionalization. The techniques used in this study showed that electroactivation altered the crystallinity and defect level of carbon surfaces, thereby leading to an improvement in the reversibility of several redox probes, as tested by cyclic voltammetry. Impedance measurements confirmed that all activated electrodes exhibited reduced charge transfer resistance. To explore possible applications of the activated carbonaceous surfaces, the reactivity of these electrodes (before and after activation) in the presence of NH 3 (aq) in alkaline medium was also studied. Activated surfaces exhibited a significant inhibition effect on both the ORR and OER in the presence of ammonia, characterized by a shift towards more positive potentials and a reduction in current intensity in both processes. In particular, activated MWCNTs showed linear dependences of the potential and maximum current intensity of the ORR peak in the ranges 50–300 mM and 0–200 mM, respectively. These results can be of interest since the activated surfaces could be applied as underlying materials for the development of highly sensitive ammonia carbon-based sensors.