Image of Carbon-Based Catalyst (IMAGE) Case Western Reserve University Caption Structure enables a carbon-based catalyst to perform comparably with metal catalysts in an acidic fuel cell. A: Carbon black agglomerates maintain a clear distance between graphene sheets imbedded with carbon nanotubes, allowing oxygen and electrolyte to flow through and speeding the oxygen-reduction reaction. B: Without the agglomerates, the sheets stack closely, stalling the reaction. Credit Liming Dai Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.