In situ construction of nitrogen-doped graphene with surface-grown carbon nanotubes as a multifactorial synergistic catalyst for oxygen reduction

Abstract Two-dimensional graphene-based materials attract much attention in catalysis due to their high specific surface area and continuous electron transport pathways. However, this material is suffering layer stacking, resulting the masked of most surface active sites, and also being detrimental to mass transfer. Based on the amine-aldehyde resin polymerization method, we constructed a multifactorial synergistic catalyst of nitrogen-doped graphene with surface in situ grown carbon nanotubes (CNTs, Co@NGC). This construction involving two to three-dimensional structural transformation not only avoids layer stacking, but further facilitates the formation of more well-dispersed Co and N species embedded into carbon networks of graphene and CNTs (to form Co N and C N active sites) and increases the accessibility of active sites. After evaluating the test results of comparative experiments, we elucidated the formation process and the activity source of the catalyst. The prepared optimal Co@NGC-800 realized praiseworthy oxygen reduction activity in alkaline media, showing an onset potential of 1.00 V (vs RHE) and a half-wave potential of 0.86 V (vs RHE). Enhanced stability attained comparing with NG (nitrogen doped graphene without the growth of CNTs), the half-wave potential of Co@NGC-800 lost only 8 mV after 40 000 s chronoamperometry.