Morphology engineering of Ni6MnO8/NiMn2O4 nanostructures through in-situ solvothermal synthesis controlling for electrochemical hydrogen storage inquiries

Abstract

Murdochite-type Ni6MnO8 based three-dimensional (3D) structures have been synthesized for electrochemical hydrogen storage. As a proof-of-concept experiment, a novel strategy is developed to fabricate the 3D hierarchical nano/microspheres Ni6MnO8/NiMn2O4 composite via a simplistic in-situ synthesis process in terms of solvothermal method. The synthesis of this type of materials was conducted in the presence of diverse of carboxylic acids such as trimesic acid, malonic acid, citric acid and succinic acid which affect on the morphology and phase structure. Different microspheres are provided by self-assembly of nano components including nanoparticles and nanorods to form microsphere, micro flower and hollow sphere. Correspondingly, changing the molar ratio of Ni:Mn led to formation of different products of Ni6MnO8 and Ni6MnO8/NiMn2O4. The resultant samples were characterized by several techniques such as XRD, EDS, FT-IR, FE-SEM, TEM, BET and VSM to better determination of purity, morphology and physical properties. The electrochemical behavior of resultant electrode materials was studied using cyclic voltammetry and chronopotentiometry technique to comparing the hydrogen storage ability. The presence of NiMn2O4 in the composite texture affects the physicochemical and electrochemical properties of Ni6MnO8 structures. The results show that hydrogen storage capacitance of hollow sphere Ni6MnO8/NiMn2O4 altered to 354 mAhg−1 after 16 cycles at 1 mA current density compared with pristine Ni6MnO8 microsphere (153 mAhg−1). Moreover, after optimizing the morphology and composition of synthesized products, the electrode materials based on Ni6MnO8/NiMn2O4 present optimistic potential for hydrogen storage application.