One-step electrochemical strategy for in-situ synthesis of S,N-codoped graphene as metal-free catalyst for oxygen reduction reaction

© 2018 Elsevier Ltd A simple and economic method was developed for synthesizing efficient S,N-codoped graphene based catalyst for oxygen reduction reaction via a one-step electrochemical exfoliation of graphite rod in melamine and (NH 4 ) 2 SO 4 mixture solution. On one hand, melamine and (NH 4 ) 2 SO 4 co-worked as electrolyte to enhance the exfoliation efficiency of graphite into graphene nanosheets. On the other hand, they also provided nitrogen and sulphur sources for in-situ codoping of the as-prepared graphene. As evidenced, the N and S elements are distributed uniformly throughout the graphene nanosheets which possessed larger interlayer spacing, more lattice disorder and higher defect density. Accordingly, the obtained SNG shows efficient ORR catalytic activity with an onset potential of 0.88 V and a dominant four-electron transfer mechanism (n = 3.98 at 0.5 V), long-time durability and excellent methanol tolerance, which are comparable or superior to those of commercial Pt/C catalysts.