Fig. 3From: Noble metal-free two dimensional carbon-based electrocatalysts for water splittinga Synthesis of N-doped graphene by using polymerization method followed by carbonization from 800 to 1000 °C. Reproduced with permissions from Ref. [81]. Copyright 2016, AAAS Science. b Illustration of the synthetic process of defective graphene. Reproduced with permission from Ref. [85]. Copyright 2016, Wiley-VCH. c Representation of the preparation of N, P-doped graphene. d, e OER polarization curves and Tafel plots of N, P-doped graphene. c–e Reproduced with permission from Ref. [87]. Copyright 2015, American Chemical SocietyBack to article page