One-step electrochemical synthesis of metallic cobalt-intercalated graphene intercalation compounds in aqueous electrolyte as high-efficiency oxygen reduction reaction catalysts

Developing highly active, stable, and cost-effective electrocatalysts is crucial for advancing electrochemical energy conversion technologies. Herein, a one-step simultaneous electrochemical exfoliation and intercalation strategy was employed to in-situ synthesize metallic cobalt-intercalated graphene intercalation compounds (Co-GIC) in an aqueous sodium hexanitrocobaltate solution. [Co(NO 2 ) 6 ] 3− anions played a dual role in promoting graphite exfoliation into graphene and serving as a cobalt source. During the process, Co ligands were first intercalated into the graphite anode, subsequently oxidized to Co 2+ , and finally reduced to metallic Co at the cathode. After nitrogen doping, the resulting metallic Co-intercalated N-doped graphene intercalation compounds (Co-N-GIC) formed a unique sandwiched electrocatalytic structure. The Co-N-GIC catalyst demonstrated excellent oxygen reduction reaction (ORR) performance in alkaline media, achieving a half-wave potential of 0.834 V vs. RHE and an electron transfer number of approximately 3.91, indicating a favorable four-electron pathway. In addition, it exhibited superior methanol tolerance and long-term durability compared to commercial Pt/C catalysts. Moreover, the Co-N-GIC catalyst delivered outstanding rechargeable Zn–air battery performance, achieving a peak power density of 248.2 mW·cm −2 and excellent cycling stability over 333 h, both of which surpassed those of commercial Pt/C. This novel one-step electrochemical synthesis strategy offers new possibilities for the preparation of graphene intercalation compound-based Co-N-C catalyst in aqueous electrolyte, presenting significant potential for energy conversion applications.