Enhanced Electrochemical Performance by Strongly Anchoring Highly Crystalline Polyaniline on Multiwalled Carbon Nanotubes

Highly crystalline polyaniline (PANI) was strongly anchored on a multiwalled carbon nanotube (MWNT) surface, slowly grown from a controlled isothermal crystallization method utilizing π-π interactions. The crystalline PANI particles are approximately 10-38 nm thick, and the space between them varies from near 0 to 55 nm as reaction conditions vary. The highly crystalline nanohybrid (CNH) showed electrochemical performance enhancement compared with that of neat MWNTs, PANI, and the reference hybrid synthesized from chemical polymerization. The specific capacitance (SC) of CNHs was 726 F g^-1 coupled with an excellent rate capability. Moreover, the strong combination between PANI and MWNTs as well as the crystalline structure in PANI improved the bulk conductivity, the interfacial charge transportation, and the cycling stability of the CNHs. The SC value of the CNHs remained almost unchanged upon 1000 charge-discharge cycles, followed by just a slight decline of 2.6% after 10 000 cycle tests. X-ray diffraction data shows the SC decline mainly resulted from the structural variation of crystalline PANI. Furthermore, the resulting CNHs showed significant electrocatalytic behavior toward H₂O₂ and exhibited a low detection limit of 4.4 μM due to the enhanced electron transportation between MWNTs and PANI. The reported method opens a gateway to design high-performance MWNT/PANI hybrids for use in electrochemical sensors, fuel cells, and energy-storage related devices.