N-doped graphene as an efficient electrocatalyst for lithium-thionyl chloride batteries

• Graphene and 900 °C-treated graphene have nonsignificant catalytic activity for Li/SOCl2 batteries.
• The N-doped graphene, synthesized easily at high-temperature pyrolysis of graphene and urea mixture, showed efficient catalytic activity to SOCl2 reduction.
• The catalytic effect on N-G is attributed to a macrocyclic substructure comprising mainly pyridinic-N, which N is incorporated into the molecular structure of graphene to change the charge distribution.
• Pyridinic-N and the adjacent C atoms form catalytic active sites in the graphene.

Nitrogen-doped graphene (N-G) catalysts, synthesized by mixing nitrogen from urea with graphene and subsequent high temperature pyrolysis, have significantly increased the discharge voltage and capacity of Li/SOCl2 batteries. The cyclic voltammetry (CV) curves and the battery discharge profiles demonstrated that the synthesis temperature of the N-G catalysts had a significant effect on the catalytic performance. A comparison of the catalytic performance of the N-G catalysts at various synthesis temperatures (600 °C, 800 °C, 900 °C) exhibited the following results: N-G-900 > N-G-800 > N-G-600. However, the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, thermogravimetric analysis (TGA) and cyclic voltammetry results suggest that the N elements incorporated in the molecular structure of graphene in the form of a “pyridinic-N” cyclic substructure at high synthesis temperatures is the critical factor in enhancing the catalytic performance of graphene, rather than “high synthesis temperatures” alone.

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