Pseudocapacitance and Excellent Cyclability of Quinones on 2D Graphene

Electrochemically active organic materials are attractive solution for the energy storage devices due to their natural abundance, relatively low cost, structural diversity and sustainability. 1,2 Conducting polymers are well studied organic systems for the supercapacitors and batteries. 3,4 Although, they exhibit high initial capacitance, their structural degradation due to ion doping/undoping leads to capacitance fade upon moderate cycling. Thus, it is needed to explore new organic materials which offer high redox capacitance, and longer cycling lifespan for the energy storage devices. Herein, we report 3D interconnected xerogel composed of redox-active 2,5-dimethoxy-1,4-benzoquinone (DMQ) decorated on reduced graphene oxide sheets (DMQ@rGO), via one-step hydrothermal method. The DMQ not only provided fast two-electron redox but also yielded an open-structured hierarchical architecture by acting as a spacer between the rGO sheets. When binder-free optimized composition of DMQ@rGO was tested as a pseudocapacitive electrode, it showed high capacitance (650 F/g, 780 F/cm 3 at 5 mV/s) and excellent capacitance retention of 99% after 25000 cycles at 50 mV/s in 1M H 2 SO 4 . Furthermore, density functional theory calculations are used to elucidate the charge storage mechanism, binding energies, adsorption orientation of DMQ, charge redistribution and density of the states. Our combined experimental and theoretical results determine that careful selection of the quinone structure, conductive substrate and electrode architecture altogether play a crucial role for high capacitance and long cycling performance. 1 B. Huskinson, M. P. Marshak, C. Suh, S. Er, M. R. Gerhardt, C. J. Galvin, X. Chen, A. Aspuru-Guzik, R. G. Gordon and M. J. Aziz, Nature , 2014, 505 , 195–8. 2 M. Boota, B. Anasori, C. Voigt, M.-Q. Zhao, M. W. Barsoum and Y. Gogotsi, Adv. Mater. , 2015, 28 , 1517–22. 3 D. Vonlanthen, P. Lazarev, K. a. See, F. Wudl and A. J. Heeger, Adv. Mater. , 2014, 26 , 5095–5100. 4 M. Boota, M. P. Paranthaman, A. K. Naskar, Y. Li, K. Akato and Y. Gogotsi, ChemSusChem , 2015, 8 , 3576–3581.