Figure 2 (IMAGE) Institute for Basic Science Caption Atomic-level tuning of Co-N4/graphene catalyst. Cobalt atoms are coordinated with four nitrogen atoms forming square planar Co-N4 structure on nitrogen-doped graphene (Co-N4/graphene). Researchers could control the charge state of cobalt atoms by introducing electron-rich (for example, oxygen) or electron-poor (for example, hydrogen) atoms near the Co-N4 structure. Specifically, when electron-rich oxygen atoms were near Co-N4 (Co-N4(O)), the charge state of cobalt atoms slightly decreased becoming electron-poor cobalt which exhibited significant enhancement on electrochemical H2O2 production. Conversely, when electron-rich hydrogen atoms were near the Co-N4 structure, Co-N4 (2H), cobalt atom became electron-rich making it less favorable for H2O2 production. Credit IBS Usage Restrictions Please indicate the credit. 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.