A lignin carbon/bismuth oxide electrode material prepared by electrostatic self-assembly with good stability in supercapacitors

In this paper, lignin carbon/bismuth oxide (LC/Bi2O3) composites were successfully synthesized. They were characterized by X-ray powder diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, etc. and their electrochemical properties were also tested. The results show that the morphology of LC/Bi2O3 composites is lignin pellets which are surrounded with Bi2O3 nanosheets. The lignin carbon in the composites mainly exists in an amorphous structure, and the presence of lignin carbon increases the specific surface area and pores of metal oxides. The electrochemical performance test shows that at the carbonization temperature of 450 °C, LC/Bi2O3 will obtain the highest specific capacitance, and after 1000 cycles of testing, the capacitance retention rate reaches 98.99%, which demonstrates that the composite material has good cycle stability. It is found that the specific capacitance of LC/Bi2O3–450 °C is 1.3 times and 1.2 times that of Bi2O3–450 °C and LC-450 °C, respectively when compared with the control group. This shows that lignin carbon and metal oxides promote and cooperate in electrochemical testing. Furthermore, the composites exhibited properties of pseudocapacitive capacitors, indicating that redox reactions occurred in electrochemical performance tests.