Accurate prediction of redox potential and the rational design of organic molecular electrode with multi-electron active centers for supercapacitor

P-benzoquinone (BQ) and derivatives represent a novel class of supercapacitor electrode materials due to their environmental friendliness, design flexibility and significant potential for rapid multi-electron faradaic reactions. But at present, the progress in guiding the structure design of electrochemical organic molecules and understanding their redox properties is still limited in explaining certain experimental phenomena related to supercapacitors. In this study, we propose an effective strategy for accurately predicting the redox potential of the organic molecular electrode (OME) through first-principles density functional theory (DFT). Additionally, we systematically investigated the impact of different functional groups and quantities on the reduction potential of 14 type BQ derivatives. We have identified a key factor that significantly affects the redox potential of OME: the electron cloud density surrounding the quinone active site (C=O). The electron-donating group (-CH 3 ) and benzene ring structure can further increase the electron cloud density around the quinone group, reducing reactivity with protons (H + ), thereby leading to a decrease in redox potential. Conversely, electron-withdrawing groups (-NO 2 ) lead to decreased electron cloud density around C O resulting in an increase in electrode potential. Furthermore, calculation results using Pearson correlation coefficients show that electron affinity (EA) has best linear correlation with reduction potential. Finally, we employed four methyl-p-benzoquinone derivatives (MBQ) as the composite organic electrode materials and achieve rapid and continuous reactions among multi-electron active centers within the designated potential window. Due to the synergistic effect from multiple molecules, MBQ-4 demonstrates an impressive specific capacitance of 681 F g −1 in 1 M H 2 SO 4 electrolyte, which is comparable to the pseudocapacitive material RuO 2 but at one-twentieth cost only.