A "One-Pot" Route for the Synthesis of Snowflake-like Dendritic CoNi Alloy-Reduced Graphene Oxide-Based Multifunctional Nanocomposites: An Efficient Magnetically Separable Versatile Catalyst and Electrode Material for High-Performance Supercapacitors.

In this paper, a simple "one pot" methodology to synthesize snowflake-like dendritic CoNi alloy-reduced graphene oxide (RGO) nanocomposites has been reported. First-principles quantum mechanical calculations based on density functional theory (DFT) have been conducted to understand the electronic structures and properties of the interface between Co, Ni, and graphene. Detailed investigations have been conducted to evaluate the performance of CoNi alloy and CoNi-RGO nanocomposites for two different types of applications: (i) as the catalyst for the reduction reaction of 4-nitrophenol and Knoevenagel condensation reaction and (ii) as the active electrode material in the supercapacitor applications. Here, the influence of microstructures of CoNi alloy particles (spherical vs snowflake-like dendritic) and the effect of immobilization of CoNi alloy on the surface of RGO on the performance of CoNi-RGO nanocomposites have been demonstrated. CoNi alloy having a snowflake-like dendritic microstructure exhibited better performance than that of spherical CoNi alloy, and CoNi-RGO nanocomposites showed improved properties compared to CoNi alloy. The value of the (CoNi)RGO-catalyzed reduction reaction of 4-nitrophenol is 20.55 × 10 s, which is comparable and, in some cases, superior to many RGO-based catalysts. The (CoNi)RGO-catalyzed Knoevenagel condensation reaction showed the % yield of the products in the range of 80-93%. (CoNi)RGO showed a specific capacitance of 501 F g (at 6 A g), 21.08 Wh kg energy density at a power density of 1650 W kg, and a retention of ∼85% of capacitance after 4000 cycles. These results indicate that (CoNi)RGO could be considered as a promising electrode material for high-performance supercapacitors. The synergistic effect, derived from the hierarchical structure of CoNi-RGO nanocomposites, is the origin for its superior performance. The easy synthetic methodology, high catalytic efficiency, and excellent supercapacitance performance make (CoNi)RGO an appealing multifunctional material.