Ionic-State Cobalt and Iron Co-doped Carbon Dots with Superior Electrocatalytic Activity for the Oxygen Evolution Reaction

Carbon dots (CDs), with abundant functional groups and unique electrical properties, have been widely exploited as an assistant in the preparation of metal-based nanohybrids for electrocatalytic water splitting, but complicated synthetic procedures and high power consumption restricted their practical application. In this work, novel ionic cobalt and iron co-doped CDs (CoFe-CDs) were synthesized in a straightforward manner through the one-step hydrothermal treatment of cobalt gluconate and ferrous gluconate salts. The CoFe-CDs exhibited superior electrocatalytic oxygen evolution reaction activity with a small overpotential of 308 mV at a current density of 10 mA/cm(2), which is comparable and even lower than those of previously reported CDs/Co, Fe-based metal composites. The activity origin of Co-II sites and the synergistic effect of Fe-III within CoFe-CDs were fully understood by DFT calculations and XPS analysis, respectively. This work provides a strategy to construct active metal-ion-doped CDs with boosted electrocatalytic activities, and such new CDs might find potential in the field of energy storage.