Fig. 4. Effect of (a-b) pyrolysis temperature, (c-d) urea dosage and
(e-f) Fe/Co ratio on the OER electrocatalytic activity of
CoFe-CoxN@NC by LSV measurement and its corresponding
Tafel slop
The stability of electrocatalyst was another key feature in practical
applications. The stability of CoFe-CoxN@NC for OER was
evaluated by the chronopotentiometri measurement recorded at a constant
current density of 10 mA·cm−2, as show in Fig. 5.
After the continuous test for 80000 s, the overpotential of
CoFe-CoxN@NC kept well-maintained, of which just
increased by about 20 mV. The TEM images, TEM-mapping images and XRD
pattern (Fig. S11-12) of CoFe-Co5.47N@NC catalyst after
stability test indicated that the structure and morphology of the
catalyst remains unchanged. From the electrocatalytic performance above,
the catalytic activity and stability of CoFe-CoxN@NC for
OER was mainly attributed to the active sites of
CoFe-Co5.47N heterogeneous structure encapsulated by the
graphic carbon layers and embedded in the nitrogen-doped lignin-derived
shell-core carbon material.