A mechanistic approach to the electrografting of carbon surfaces and electrochemical properties of the grafted films – A critical review

Modification of carbon surfaces by electrografting is a relevant topic due to its potential applications in different fields of science, which has motivated the publication of many works focused on different methodologies to get covalently attached films or to study their properties. Diverse organic molecules have been found to be able to produce grafted films on carbon-based electrodes and their reduction or oxidation involve free radicals that participate in complex reaction mechanisms, from the incipient radical attack of the electrode surface until the film growth. Once the grafted film is generated, electron conduction as well as mass transport through this film are processes that depend on many experimental factors, which are still susceptible of further studies. Hence, the knowledge of the grafting mechanisms is always useful for designing grafted films with more specific and controlled properties. Therefore, this critical review is focused to the main mechanistic aspects of different electrochemical methodologies to get grafted films on carbon surfaces. The use of cyclic voltammetry as tool of modification and characterization of electrochemically active films is summarized. Information about the use of reversible redox probes as indirect method to infer structural information of grafted films is also discussed. Structural reorganization, permeation processes, supporting electrolyte effects and rectification of voltametric responses of redox probes on grafted electrodes were also considered.