Gaire Madhu, Khatoon Najma, Chrisey Douglas
Department of Physics and Engineering Physics, School of Science and Engineering, Tulane University, New Orleans, LA 70118, USA.
Nanomaterials (Basel). 2021 Mar 12;11(3):717. doi: 10.3390/nano11030717.
We report a photonic technique to instantaneously synthesize cobalt oxide reduced graphitic oxide (CoO-rGO) supercapacitor electrodes. The electrode processing is achieved through rapidly heating the precursor material by irradiation of high-energy pulsed mostly visible light from a xenon lamp. Due to the short duration of the light pulse, we prepared the electrodes at room temperature instantaneously (ms), thus eliminating the several hours of processing times of the conventional techniques. The as-prepared electrodes exhibited a highly porous morphology, allowing for enhanced ionic transport during electrochemical interactions. The electrochemical properties of the CoO-rGO electrodes were studied in 1 M KOH aqueous electrolyte. The non-rectangular cyclic voltammetry (CV) curves with characteristic redox peaks indicated the pseudocapacitive charge storage mechanism of the electrodes. From the discharge curves at 0.4 mA/cm and 1.6 A/g constant current densities, the electrode showed areal specific capacitance of 17 mF/cm and specific capacitance of 69 F/g, respectively. Cyclic stability was tested by performing 30,000 galvanostatic charge-discharge (GCD) cycles and the electrode exhibited 65% capacitance retention, showing its excellent electrochemical performance and ultra-long cycle life. The excellent electrochemical electrode properties are attributed to the unique processing technique, optimum processing parameters, improved conductivity due to the presence of rGO, and highly porous morphology which offers a high specific surface area. The novel photonic processing we report allows for high-temperature heating of the precursor films achieved via non-radiative recombination of photogenerated electron holes pairs during irradiation. Such extremely quick (ms) heating followed by instantaneous cooling results in the formation of a dense and robust bottom layer of the electrode, resulting in a long cycle life.
我们报道了一种光子技术，可即时合成氧化钴还原氧化石墨烯（CoO-rGO）超级电容器电极。通过用氙灯发出的高能脉冲可见光照射前驱体材料来快速加热，从而实现电极制备。由于光脉冲持续时间短，我们在室温下瞬间（毫秒级）制备了电极，从而消除了传统技术所需的数小时处理时间。所制备的电极呈现出高度多孔的形态，有利于在电化学相互作用期间增强离子传输。在1 M KOH水性电解质中研究了CoO-rGO电极的电化学性能。具有特征性氧化还原峰的非矩形循环伏安（CV）曲线表明了电极的赝电容电荷存储机制。在0.4 mA/cm²和1.6 A/g的恒流密度下，从放电曲线可知，该电极的面积比电容分别为17 mF/cm²和比电容为69 F/g。通过进行30,000次恒电流充放电（GCD）循环测试了循环稳定性，该电极表现出65%的电容保持率，显示出其优异的电化学性能和超长的循环寿命。优异的电化学电极性能归因于独特的加工技术、最佳的加工参数、由于rGO的存在而提高的导电性以及提供高比表面积的高度多孔形态。我们报道的新型光子加工方法允许在前驱体薄膜照射期间通过光生电子空穴对的非辐射复合实现高温加热。这种极快（毫秒级）的加热随后立即冷却导致形成致密且坚固的电极底层，从而实现长循环寿命。
