During the synthesis of fullerenes by dc plasma arcs, it has been found that the anodic graphite rod consistently burns up, while the cathodic graphite rod grows slag at its end. Further investigations revealed that the anodic and cathodic graphite rods played different roles in forming fullerenes in plasma arcs. The anodic graphite rod contributed to the formation of all products in de plasma arcs, while the cathodic one played a role only as an electrode. These results suggest that an electrochemical mechanism occurs during fullerene formation in plasma arcs. Temperature measurements indicate that, in the stable plasma are in our experiment, the temperature of the graphite rods was lower than their sublimation point, thus confirming the involvement of an electrochemical mechanism in the fullerene formation process in de plasma arcs. The relationship of the fullerene formation rate to the cell voltage supports the point.