Polyvinylpyrrolidone-modified Bi2O3 and Bi2S3 nanocomposites for improved supercapacitive performance

In this work, Bi 2 O 3 and Bi 2 S 3 nanomaterials are modified with polyvinylpyrrolidone (PVP). The products are defined as Bi 2 O 3 @PVP and Bi 2 S 3 @PVP, respectively. SEM demonstrates that the addition of PVP helps to reduce the size of Bi 2 O 3 and Bi 2 S 3 nanomaterials. XRD exhibits that the structure of Bi 2 O 3 changed from α-Bi 2 O 3 to β-Bi 2 O 3 @PVP due to the addition of PVP, while the Bi 2 S 3 configuration remained unchanged. XPS demonstrates that excess PVP leads to a partial reduction of trivalent Bi 3+ to metallic Bi 0 . Their supercapacitive performances are tested and it is found that appropriate PVP can improve the capacitive performance and cyclic stability of both Bi 2 O 3 and Bi 2 S 3 . The specific capacitance of Bi 2 O 3 @1 g PVP is 1.4 times that of the pristine Bi 2 O 3 , and the specific capacitance of Bi 2 S 3 @1 g PVP is 1.8 times that of the pristine Bi 2 S 3 . Compared with 82.0% Bi 2 O 3 and 79.6% Bi 2 S 3 , the cyclic retention is 94.7% and 95.2% for Bi 2 O 3 @1 g PVP and Bi 2 S 3 @1 g PVP after 10,000 cycles. The reason for enhancement is that PVP can support Bi 2 O 3 and Bi 2 S 3 materials, not only to support their structural stability but also to reduce their size and facilitate electron transfer and ion diffusion.