Comparison of the Electrochemical Response of Carbon-Fiber-Reinforced Plastic (CFRP), Glassy Carbon, and Highly Ordered Pyrolytic Graphite (HOPG) in Near-Neutral Aqueous Chloride Media

resumo

Carbon-fiber-reinforced polymers (CFRP), being conductive, are capable of supporting cathodic oxygen reduction reactions (ORR) and thus promote galvanic corrosion when coupled to many metallic materials. Hence, understanding cathodic processes at carbon surfaces is critical to developing new strategies for the corrosion protection of multi-material assemblies. In the present work, the electrochemical responses of CFRP, glassy carbon, and HOPG (Highly Ordered Pyrolytic Graphite) have been evaluated in a quiescent 50 mM NaCl solution, and their respective activities towards ORR have been ranked. Employing the averages of the specific charges (CFRP, 129.52 mC cm(-2); glassy carbon, 89.95 mC cm(-2); HOPG, 60.77 mC cm(-2)) passed during 1 h polarization of each of the 3 carbon surfaces at -1000 mV(SCE) in the test media as a ranking criterion, the propensities of the 3 carbon surfaces (CFRP, GC, and HOPG) to support cathodic activities that can lead to anodic metal dissolution on galvanic coupling to metallic materials are ranked thusly; CFRP > GC > HOPG. This ranking is consistent with the trend of capacitance values obtained in this work: CFRP (19.5 to 34.5 mu F cm(-2)), glassy carbon (13.6 to 85.5 mu F cm(-2)), and HOPG (1.4 to 1.8 mu F cm(-2)). A comparison of electrochemical data at potentials relevant to galvanic coupling to metals indicated that at these cathodic potential(s) the CFRP surface is the most electrochemically active of the studied carbon surfaces. On the basis of the values and trends of the electrochemical parameters evaluated, it is postulated that the observed differences in the electrochemical responses of these 3 carbon-rich surfaces to ORR are significantly due to differences in the proportions of edge sites present on each carbon surface. These results could provide valuable insights on plausible strategies for designing carbon surfaces and carbon fiber composites with reduced activity toward ORR for corrosion protection applications or enhanced activity towards ORR for energy applications.

palavras-chave

OXYGEN REDUCTION REACTION; ELECTRON-TRANSFER KINETICS; SCANNING-TUNNELING-MICROSCOPY; BASAL-PLANE GRAPHITE; GRAPHENE OXIDE-FILMS; EDGE-PLANE; DIFFERENTIAL CAPACITANCE; DOUBLE-LAYER; ELECTROCATALYTIC ACTIVITY; COVALENT MODIFICATION

categoria

Materials Science

autores

Ofoegbu, SU; Ferreira, MGS; Nogueira, HIS; Zheludkevich, M

Grupos

G1 - Materiais Porosos e Nanossistemas
G3 - Materiais Eletroquímicos, Interfaces e Revestimentos

Projectos

Corrosion adn corrosion protection in multi-material systems (PTDC/CTM/108446/2008)

CICECO - Aveiro Institute of Materials (UID/CTM/50011/2013)

agradecimentos

S.U. Ofoegbu acknowledges Fundacao para a Ciencia e a Tecnologia (FCT) Portugal for the doctoral grant (SFRH/BD/75167/2010). Funding from FCT project: "Corrosion and Corrosion Protection in Multi-material Systems", (PTDC/CTM/108446/2008), and European FP7 project: "Active PROtection of multi-material assemblies for AIRcrafts" ["PROAIR" (PIAPP-GA-2013-612415)] are acknowledged. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and, when appropriate, co-financed by FEDER under the PT2020 Partnership Agreement.