Makkar Priyanka, Chandel Madhurya, Patra Manoj Kumar, Ghosh Narendra Nath
Nano-materials Lab, Department of Chemistry, Birla Institute of Technology and Science, Pilani K K Birla Goa Campus, Zuarinagar, Goa 403726, India.
Defence Lab, Jodhpur 342011, India.
ACS Omega. 2019 Nov 25;4(24):20672-20689. doi: 10.1021/acsomega.9b02861. eCollection 2019 Dec 10.
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.
本文报道了一种简单的“一锅法”合成雪花状树枝状CoNi合金还原氧化石墨烯（RGO）纳米复合材料的方法。基于密度泛函理论（DFT）进行了第一性原理量子力学计算，以了解Co、Ni与石墨烯之间界面的电子结构和性质。针对两种不同类型的应用，对CoNi合金和CoNi-RGO纳米复合材料的性能进行了详细研究：（i）作为4-硝基苯酚还原反应和Knoevenagel缩合反应的催化剂；（ii）作为超级电容器应用中的活性电极材料。在此，展示了CoNi合金颗粒微观结构（球形与雪花状树枝状）的影响以及CoNi合金固定在RGO表面对CoNi-RGO纳米复合材料性能的影响。具有雪花状树枝状微观结构的CoNi合金表现出比球形CoNi合金更好的性能，并且CoNi-RGO纳米复合材料相比于CoNi合金表现出改进的性能。（CoNi）RGO催化4-硝基苯酚还原反应的值为20.55×10 s，与许多基于RGO的催化剂相当，在某些情况下甚至更优。（CoNi）RGO催化的Knoevenagel缩合反应产物的产率在80 - 93%范围内。（CoNi）RGO在6 A g时的比电容为501 F g，在功率密度为1650 W kg时的能量密度为21.08 Wh kg，在4000次循环后电容保持率约为85%。这些结果表明（CoNi）RGO可被视为一种有前景的高性能超级电容器电极材料。CoNi-RGO纳米复合材料的分级结构产生的协同效应是其优异性能的根源。简便的合成方法、高催化效率和优异的超级电容性能使（CoNi）RGO成为一种有吸引力的多功能材料。
