Nickel and Nickel Hydroxide synergism in Alkaline HER as the Non NobelMetal Nanoparticles Decorated on the Reduced Graphite Oxide

The development of clean electrochemical energy conversion technologies such as fuel cells andelectrolyzers is considered for both of high performance and cost effective properties. Therefore,many attempts have noticed to replace Pt group metals by non-noble ones such as nickel, cobaltand etcetera. For this purpose, it is necessary to improve non noble metals catalytic activity byvarious methods such as development of supports, hybridization and alloying.In this work, a novel catalyst was synthesized by hybridization of nickel and nickel hydroxide onthe reduced graphite oxide (Ni-3Ni(OH)2. 2H2O /rG) via a facile and cost effective glycerolmediated solvothermal procedure. The catalyst was evaluated toward the hydrogen evolutionreaction (HER) and compared with Ni-rG and 3Ni(OH)2, 2H2O/rG which had been synthesized withthe same method. The structure and morphology of the samples were characterized by X-raydiffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infraredspectroscopy (FT-IR) techniques. After that, the catalysts were investigated for HER activity byusing a conventional three-electrode electrochemical cell in alkaline media.Fig. 1 shows the XRD patterns of the samples at three furnace temperatures. Interpretation ofresults clearly showed that by increasing the furnace temperature, nickel characteristic peaksappears at 2θ= 44.3, 51.7 and 76.2 ○ which were corresponded to (111), (200) and (220) planes ofcubic Ni (JCPDS 04-0850) [1]. The HER activities of three catalysts were investigated in KOH (1M) solution. As shown in Fig. 2, Ni-3Ni(OH)2. 2H2O /rG shows the highest electrocatalytic activitycompared with others due to synergetic effect between nickel and nickel hydroxide. The edges ofNi(OH)2 participate in dissociative adsorption of water and the production of hydrogen andhydroxyl intermediates [2]. Then, hydrogen adsorption and recombination into H2 on the nearby Nisites would be take place. For this reason, lowest tafel slope (b), onset overpotential (ηonset), η10(overpotential at 10 mA cm-2) and η50 as well as highest exchange current density (j0) were obtainedfor Ni-3Ni(OH)2. 2H2O /rG.

Keywords:

Metal Nanoparticles , hydrogen evolution , alkaline media , synergetic effect