Anthraquinone-Catalyzed TEMPO Reduction to Realize Two-Electron Energy Storage of Poly(TEMPO-methacrylate)

2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) functional polymers are a type of organic electroactive material featuring a two-electron redox process. However, the electrochemical reduction of TEMPO (TEMPO^•/-) is rarely adopted for energy storage due to its slow reaction kinetics. Here, we report using anthraquinone (AQ) as an organic redox mediator to promote TEMPO reduction kinetics. The catalytic effect of AQ is verified by electrochemical in situ FTIR spectroscopy in a model three-electrode system and further evidenced by cyclic voltammetry and chronoamperometry, providing a turnover frequency of 69 h^-1. To exemplify the AQ catalytic effect in energy storage performance, we incorporate AQ groups into a typical TEMPO polymer (i.e., poly(TEMPO-methacrylate), PTMA). The AQ-catalyzed TEMPO reduction and AQ/carbon π-πinteraction synergistically reduce the heterogeneous charge transfer resistance and accelerate the kinetics of the TEMPO^•/-process in the PTMA electrode. The half-cell tests of the AQ functional PTMA show two prominent discharge plateaus with an initial capacity of 174 mAh g^-1and a 0.18% capacity loss per cycle. Moreover, the discharge capacity based on the TEMPO^•/-couple is about 85 mAh g^-1, 30% higher than that of the pristine PTMA. This new strategy could be widely applied to various organic redox systems to enhance their electrochemical kinetics and particularly improve the energy storage performance of organic polymer redox materials.