context: To further probe the electrochemical performance of the UTCNF, a kinetic analysis was conducted. Fig. 4a shows the CV curves of the UTCNF at different scan rates. The redox electrochemical reactions occurring on the UTCNF may be described as the reversible reactions Ni(OH)2 + OH− ↔ NiOOH + H2O + e− and Co(OH)2 + OH− ↔ CoOOH + H2O + e−. According to the formula i = k1v + k2v1/2 (i and v are the current and scan rate), i at a given potential can be divided into capacitive limited effects (k1v) and diffusion-controlled effects (k2v1/2). As illustrated in Fig. 4b, the detailed capacitive fraction (blue region) was calculated to be 35.8% at 0.5 mV s−1. Moreover, the capacitive contributions at 0.1 and 1 mV s−1 were also determined (Fig. 4c) to be 20.6% and 40.4%, respectively, which indicates that the electrochemical process is controlled by both capacitive behavior and diffusion. Fig. 4d shows the Nyquist plots of the UTCNF//Zn battery and the CNF//Zn battery, and the fitting values are listed in Table S3.† The UTCNF//Zn battery shows a larger charge transfer resistance Rct (4.1 Ω) than that of the CNF//Zn battery (2.4 Ω), which may be due to the decreased conductivity due to in situ formation of cobalt/nickel composite hydroxides after ultrasonic treatment. Such a markedly enhanced performance of the UTCNF//Zn battery may be attributed to the formed surface-active materials and the unique porous structure of the UTCNF cathode.
answer: UTCNF 