Facile synthesis of petal-like NiCo/NiO-CoO/nanoporous carbon composite based on mixed-metallic MOFs and their application for electrocatalytic oxidation of methanol

Abstract

Porous carbon template decorated with mixed transition metals/metal oxides with tunable architecture is becoming increasingly important and attractive as a kind of novel electrode materials. In this way, mixed-metallic metal-organic frameworks (MOFs) provide an opportunity for fabrication of homogeneous mixed metals/metal oxides distribution in the porous carbon frame without any carbon precursor additive. Also, structures, dimensions and electrochemical performance of MOFs can be readily manipulated by simply tuning the metals molar ratio. In this study, we demonstrate the design and fabrication of petal-like NiCo/NiO-CoO metal/metal oxides with a rational composition embedded in 3D ultrathin nanoporous carbon composite)NiCo/NiO-CoO/NPCC(. This nanocomposite is synthesized by a two-steps procedure involving preparation of bimetallic MOFs by partially substituting Ni2+ in the Ni-MOF structure with Co2+ (Ni-Co/BDC [BDC = 1,4-Benzene dicarboxylic acid]) and direct carbonization process in the N2 atmosphere at 900 °C. The prepared nanocomposite was used directly as a non-precious electrocatalyst for methanol oxidation reaction. The results indicated that, in comparison to the monometallic metal/metal oxides distributed in nanoporous carbon composite (Ni/NiO/NPCC and Co/CoO/NPCC), the mixed metals/metal oxides NiCo/NiO-CoO/NPCC exhibits excellent electrochemical performance toward the anodic oxidation of methanol. The unique ultrathin porous petal-like structure with free pores and the enlarged specific surface area provides fast ion/electron transfer, leading to faster kinetics, lower over-potential, and higher electro-catalytic reactivity. Besides their intriguing structural features, the excellent conductivity of carbon frame, as well as a rational composition of two constituents and synergistic effects from cobalt, nickel and their oxides provides favorable catalytic activity for the electro-oxidation of methanol. Therefore, it is believed that this novel multi-component composites demonstrates good electrocatalytic activity and suitable stability towards the methanol oxidation.