Synthesis of ternary CoZnAl layered double hydroxide and Co-embedded N-doped carbon nanotube hollow polyhedron nanocomposite as a bifunctional material for ORR electrocatalyst and supercapacitor electrode

Abstract

The construction of non-precious and high-performance nanomaterial is the current hotspot in oxygen reduction reaction and supercapacitor applications. Herein, a novel composite consisting of a three-metal layered double hydroxide (CoZnAl-LDH) and a ZIF-derived carbon base (Co/NCNHP) is proposed, which is fabricated by the hydrothermal synthesis of CoZnAl-LDH and the in situ loading of Co/NCNHP in different ratios of 10, 20, and 30 %. The synthesized nanomaterials were evaluated by various physical and electrochemical tests. The results manifest that the addition of Co/NCNHP with a carbon nanotube hollow polyhedron morphology to the flower-like CoZnAl-LDH had a remarkable impact on its morphology and properties, such that it elevates the surface area, enhances mass and electron transfer, and improves electrical conductivity of the final product. Based on the results, the CoZnAl-LDH@Co/NCNHP 20 % indicated better electrochemical performance than other synthesized samples. This composite offered excellent ORR catalytic activity with an onset potential of −0.043 V vs. Ag/AgCl in alkaline electrolyte, 4-electrons path selectivity (average electron transfer number = 3.69), and high durability. Furthermore, it exhibited a superior capacitance performance of 869.6 F.g−1 at a current density of 1 A.g−1 and superior cycling stability (92.7 % capacitance retention at 2 A.g−1 after 1000 cycles). Therefore, according to the test results, the final as-prepared nanocomposite possesses a desirable electrochemical performance in both ORR and supercapacitor applications.