Easy synthesis of N-doped graphene by milling exfoliation with electrocatalytic activity towards the Oxygen Reduction Reaction (ORR) Juan C. Carrillo-Rodrı´guez a , Ivonne L. Alonso-Lemus b,* , A.A. Siller-Ceniceros c , E. Martı´nez G d , Pedro Piz  a-Ruiz e , Gregorio Vargas-Guti  errez a , F.J. Rodrı´guez-Varela a,c a Sustentabilidad de Los Recursos Naturales y Energı´a, Centro de Investigacion y de Estudios Avanzados Del IPN Unidad Saltillo, Av. Industria Metalu´ rgica, Parque Industrial Saltillo Ramos Arizpe, C.P. 25900, Ramos Arizpe, Coah, Mexico b CONACyT, Centro de Investigacion y de Estudios Avanzados Del IPN Unidad Saltillo, Mexico c Nanociencias y Nanotecnologı´a, Centro de Investigacion y de Estudios Avanzados Del IPN Unidad Saltillo, Mexico d Centro de Investigacion en Materiales Avanzados S.C., Alianza Norte 202, PIIT, Carretera Monterrey-Aeropuerto Km. 10, Apodaca, NL, C.P. 66628, Mexico e Centro de Investigacion en Materiales Avanzados S.C., Av. Miguel de Cervantes 120, Parque Industrial Chihuahua, C.P. 31109, Chihuahua, Chih, Mexico article info Article history: Received 5 April 2017 Received in revised form 9 August 2017 Accepted 11 August 2017 Available online xxx Keywords: N-doped graphene Metal-free electrocatalyst Mechanical milling Low temperature fuel cells abstract We report a novel process to synthesize graphene (G) catalyst by mechanical milling using graphite flakes as the precursor. G sample has been doped ex situ with hydrazine as ni- trogen source via solvothermal procedure to obtain the G D1 catalyst. In a second approach, the G D2 sample has been synthesized doping G with uric acid as nitrogen precursor in situ, i.e., during the milling step. Doping with nitrogen increases the I D /I G Raman spectra ratios of G D1 and G D2 to 1.52 and 1.12, respectively, higher than 1.02 of G. XPS analysis shows that Pyridinic, Amine, Pyrrolic, Graphitic and Oxidized nitrogen are formed at G D1 , while only Pyrrolic is present at G D2 . Evaluation of catalytic activity for the ORR in 0.5 mol L 1 KOH shows an increase in onset potential (E onset ) of the ORR at G D1 , compared to G and G D2 .G D1 also generated a higher current density (j) at 0.83 V than G and G D2 . The results show that mechanical milling is an efficient method to synthesize G. Even though, the doping can still be improved to form more Nitrogen that promotes the ORR, specifically Pyridinic N and Graphitic N. © 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Introduction The Oxygen Reduction Reaction (ORR) is the kinetically limiting part of low-temperature fuel cell devices [1]. Consequently, the use of materials with high catalytic activity is required in order to improve the kinetics at the fuel cell cathode. On this context, Pt is widely applied as cathode catalyst because of its high performance for the ORR. How- ever, it is a costly material with reduced abundance, * Corresponding author. E-mail addresses: ivalemus@gmail.com, ivonne.alonso@cinvestav.edu.mx (I.L. Alonso-Lemus). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2017) 1 e6 http://dx.doi.org/10.1016/j.ijhydene.2017.08.084 0360-3199/© 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Carrillo-Rodrı´guez JC, et al., Easy synthesis of N-doped graphene by milling exfoliation with elec- trocatalytic activity towards the Oxygen Reduction Reaction (ORR), International Journal of Hydrogen Energy (2017), http://dx.doi.org/ 10.1016/j.ijhydene.2017.08.084