Highly controlled synthesis of nanoprickly nickel@nickel oxide formed on carbon black/reduced graphene oxide nanosheets: Charge-storage performance and electrocatalytic activity for methanol oxidation

Abstract

Supercapacitive performance and electrocatalytic activity of the nickel@nickel oxide core@shells (Ni@NiO), formed with different composition, structure, and morphology via electroless deposition on the surface of carbon black/reduced graphene oxide nanosheets (CB/RGONs) in the presence of citrate ion are reported here. The conditions are controlled and the synthesis is carried out systematically via three different routes: (a) in the absence of CB and citrate ion, (b) just in the presence of CB, and (c) in the presence of both CB and citrate ion. Then, the synthesized composites were transferred onto the GC electrodes, leading to (a) GC-RGONs-PNi@NiO(Particles), (b) GC-RGONs-HENi@NiO(Hedgehog), and (c) GC-CB/RGONs-NPNi@NiO(Nanoprickly) systems, respectively. The synthesis process is followed by several surfaces and electrochemical techniques, from which the physicochemical behaviors of the prepared composites and electrode systems were determined, and the systems were characterized. Then, their activities for capacitive charge storage and electrooxidation of methanol were quantitatively studied. The composite fabricated under optimized conditions, Nanoprickly system, exhibited (i) the most efficient charge storage behavior with specific capacitance (Cs) of 2398 F g−1; and (ii) a large electrocatalytic activity for electrooxidation of methanol with peak current density of 154 A g−1 at 10 mV s−1, compared with values of 1451 & 1049 F g−1 and 72 & 58 A g−1 obtained for the composite ancestors, Hedgehog and Particle systems, respectively. The increase in the Cs and improvement in the electrocatalytic activity of the nanocomposite are attributed to the (i) crucial role of CB nanospacer, preventing graphene layers from restacking, (ii) role of RGONs, dispersing and stabilizing of Ni@NiO nanoprickly particles, and (iii) synergetic chemical coupling effect between NPNi@NiO and CB/RGONs.