Graphitized carbon as an efficient mesoporous layer for unitized regenerative fuel cells

To enhance the electrochemical performance of membrane electrode assemblies (MEAs) for unitized regenerative fuel cells (URFCs), we prepared and introduced graphitized-carbon (Gr-carbon) of high crystallinity as a mesoporous layer (MPL) in MEAs. The round-trip energy conversion efficiencies (εRT (%)) of non-MPL, typical amorphous-carbon (Am-carbon) MPL and Gr-carbon MPL containing MEAs at the current density of 1 A cm−2 were 36.6, 41.8, and 43.8, respectively. The overall round trip energy efficiency was considerably higher for the graphitized form of mesoporous carbon. For Gr-carbon, a high stability of the round-trip energy conversion efficiency was achieved even after 20th cycles (42.3%) owing to the enhanced electrical conductivity and high crystallinity of Gr-carbon after thermal treatment. Therefore, Gr-carbon considerably enhances the ORR and OER performances and prevents carbon corrosion and surface oxidation during the fuel cell and water electrolyzer modes in the URFC system.