Nanoarchitectonics for Pentagon Defects in Carbon: Properties and Catalytic Role in Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is a crucial process in electrochemical energy technologies, featuring fuel cells and metal-air batteries in the coming carbon-neutral society. Carbon materials have garnered significant attention as economical, sustainable alternatives to precious metal catalysts. In particular, there have been increasing reports recently that pentagons introduced into graphitic carbons promote catalytic activity for ORR. In addition, interesting studies are reported on carbon materials' synthesis, characterization, and spin polarization properties with pentagonal defects. This review comprehensively summarizes the formation mechanism, characterization, spin, oxygen (O₂) adsorption, and ORR catalytic activity of carbon catalysts with pentagonal defects. By connecting the dots between theoretical insights and experimental results, this review elucidates the fundamental principles governing pentagon-related activity and offers perspectives on future directions for designing efficient ORR catalysts based on carbon materials.