Single, double and triple cobalt atoms confined in 2D regular framework for oxygen electrocatalysis

Abstract Many natural metalloenzymes consist of multi-nuclear metal sites. The multiple metal centers trigger a cooperative catalytic effect that decreases the reaction energy barrier. However, it remains a grand challenge in mimicking the metalloenzymes in heterogeneous catalysts. C2N is an emerging 2D material with a predictive regular holey framework. Its large hole with a diameter of ~ 8.35 A contains three pairs of pyridinic nitrogen, allowing the capture of transition metals from single to triple atoms. Based on quantum chemistry calculations, we find that the introduction of double (Co2@C2N) and triple cobalt (Co3@C2N) atom clusters turns C2N nanosheet from semiconducting into a nearly metallic state. The confined double or triple atoms can work cooperatively toward oxygen reduction and evolution reaction (ORR and OER). Impressively, with the activation barrier of 0.57 eV, Co3@C2N is a competitive novel candidature that can substitute bulk Pt catalyst (~0.80 eV). In-depth analysis indicates that the formation of an oxo-doped field environment is the key to realize efficient oxygen electrocatalysis.