Fig 1.
Preparation of Bi/C-TCF.
Fig 2.
(a) SEM image and corresponding EDS mapping of Bi/C nanoparticles.
(b) HRTEM image of Bi/C nanoparticles. (c) SEM image of untreated TCF. (d) SEM image and EDS mapping of Bi/C-TCF. (e) Cross-sectional views of water droplet contact angles on CF, TCF, C-TCF, and Bi/C-TCF surfaces.
Fig 3.
(a) XRD patterns of C particles, Bi particles, Bi/C particles, TCF, Bi/C-TCF, and standard PDF card of Bi.
(b) XPS survey scan of Bi/C-TCF composite. High-resolution XPS spectra of (c) C 1s region, (d) O 1s region, and (e) Bi 4f region.
Fig 4.
(a) CV curves of TCF, C-TCF, Bi-TCF, and Bi/C-TCF recorded at a scan rate of 10 mV/s.
(b) Statistical table of peak currents ( and
) and peak potential separations (
) derived from the CV curves. (c) Nyquist plots of the EIS of TCF, C-TCF, Bi-TCF, and Bi/C-TCF. (d) The equivalent circuit of the EIS. (e)
and
values of TCF, C-TCF, Bi-TCF, and Bi/C-TCF. (f) Tafel polarization curves of TCF, C-TCF, Bi-TCF, and Bi/C-TCF. (g)-(h) Tafel slope curves.
Fig 5.
(a) Rate performance of VRFBs with TCF and Bi/C-TCF as anodes, respectively.
(b)-(c) The capacity-voltage curves for VRFBs with TCF and Bi/C-TCF anodes at different current densities. (d)-(e) The GITT profiles of the VRFBs with TCF and Bi/C-TCF anodes at 40 mA/cm2, respectively. (f) The power density and polarization curves of VRFBs with TCF and Bi/C-TCF anodes, respectively.
Fig 6.
(a) The EE and VE of VRFB stacks with TCF, C-TCF and Bi/C-TCF as negative electrodes.
(b) Photographs of the TCF electrode (left) and Bi/C-TCF electrode (right) before and after cycling. (c) SEM images of the TCF electrode after cycling. (d) SEM images of the Bi/C-TCF electrode after cycling. (e) CV curves of the electrodes after cycling. (f) Statistical table of ,
and
from the CV curves.