Grinding to produce polydopamine-modified polypyrrole nanotubes with enhanced performance for sodium-ion capacitor

Conductive polymers have a great potential for application in electrochemical energy-storage systems (EES). However, the structural instability due to the swelling/shrinking of polymer chains during charge/discharge cycles hampers the wide use of conductive polymers in EES. In this paper, polypyrrole nanotubes (PNTs) are first produced by a methyl orange-templated method. The influence of the feeding sequence of reactants on the size, morphology, specific surface area, and conductivity of PNTs is explored. Second, a composite of polydopamine (PDA)-modified PNTs (PNT/PDA) is produced by grinding PNTs with dopamine hydrochloride (DAH) in N -methyl pyrrolidone. Dopamine in situ transforms into PDA modifier while PNTs are in situ doped by the hy-drochloride. The effect of DAH/PNTs weight ratio on the electrode performance is investigated. The specific capacitance is doubled and the capacitance retention is increased by 26% for PNT/PDA after 1000 cycles at 1 A g-1, compared with pristine PNTs. Also, the asymmetric PNT/PDA||MnO2 sodium-ion capacitor presents a capacitance retention of 83.7% after 10,000 cycles with varying current densities in the range of 0.5-5 A g-1, higher than that of 70.5% for PNT-based counterpart. The enhanced electrochemical performance of PNT/PDA is attributed to the in situ acid doping and the electron transfer from PDA to PNTs due to the catecholic chemistry.

Automated summary

This study investigates the application of polypyrrole nanotubes (PNTs) in electrochemical energy-storage systems (EES). The researchers developed a composite of polydopamine (PDA)-modified PNTs and found that it exhibited enhanced electrochemical performance, with higher capacitance retention and specific capacitance compared to pristine PNTs.