Preparation and evaluation of a new hybrid support based on exfoliation of graphite by ball milling for Ni nanoparticles in hydrogen evolution reaction Fariba Jalili, Mohammad Zhiani * , Saeedeh Kamali Department of Chemistry, Isfahan University of Technology, Isfahan, 84156-83111, Iran article info Article history: Received 12 May 2018 Received in revised form 18 September 2018 Accepted 28 September 2018 Available online xxx Keywords: Ni nanoparticles Graphene- graphite hybrid support Hydrogen evolution reaction Ball milling abstract A mixture of graphene/graphite as new support was prepared by ball milling procedure and was used for Nickel nanoparticles supported that was employed as a cathode catalyst for hydrogen evolution reaction (HER) in the KOH solution. The structure and electrocatalytic activity of electrocatalyst were investigated by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, and electrochemical techniques. The results indicated that by raising the time of the ball milling from 0 to 270 min, the HER activity of electrocatalyst first increased, and then decreased according to the increase of active sites and then agglomeration of Ni nanoparticles. Ni nanoparticles supported on the mixture with 180 min ball milling exhibited the highest HER activity with a low overpotential (205 mV at 10 mA cm 2 ), Tafel slope of 84 mV dec 1 , and remarkable durability. © 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Introduction Hydrogen, as a large-scale energy carrier, is pollution-free and efficient fuel. Water Electrolysis is a way of hydrogen pro- duction through a simple, clean and renewable method [1]. However, providing low-cost and durable catalysts for hydrogen evolution reaction (HER) was always a challenge in electrolysis development. At present, many types of research have been devoted to the optimization of none-noble metals as the electrocatalysts for the HER. Therefore, transition metals are attractive, since transition metals possess the remarkable properties such as low-cost, low electrical Resis- tance, acceptable stability and selectivity in alkaline media and facile employment as the catalysts [2]. The most impor- tant challenges ahead of commercial applications of the transition metals are low electrocatalytic activity and poor chemical stability. Two approaches have been developed to solve the problems; (a) alloying of transition metals with a second metal element, (b) using of carbon substances such as carbon nanotube, graphene, and graphite as the catalyst supporter due to their stability in both acidic and alkaline media [2,3]. Graphite is built of many graphene sheets which are kept together weakly by van der Waals forces. Graphene is the initial unit, obtained by exfoliation of the natural graphite [4,5]. Graphene has been generally employed in various fields such as hydrogen storage [6], electrodes of capacitors [7], electrodes * Corresponding author. E-mail address: m_zhiani@cc.iut.ac.ir (M. Zhiani). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2018) 1 e9 https://doi.org/10.1016/j.ijhydene.2018.09.202 0360-3199/© 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Jalili F, et al., Preparation and evaluation of a new hybrid support based on exfoliation of graphite by ball milling for Ni nanoparticles in hydrogen evolution reaction, International Journal of Hydrogen Energy (2018), https://doi.org/ 10.1016/j.ijhydene.2018.09.202