Polyvinylpyrrolidone-modified Bi2O3 and Bi2S3 nanocomposites for improved supercapacitive performance

In this work, Bi2O3 and Bi2S3 nanomaterials are modified with polyvinylpyrrolidone (PVP). The products are defined as Bi2O3@PVP and Bi2S3@PVP, respectively. SEM demonstrates that the addition of PVP helps to reduce the size of Bi2O3 and Bi2S3 nanomaterials. XRD exhibits that the structure of Bi2O3 changed from alpha-Bi2O3 to beta-Bi2O3@PVP due to the addition of PVP, while the Bi2S3 configuration remained unchanged. XPS demonstrates that excess PVP leads to a partial reduction of trivalent Bi3+ 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 Bi2O3 and Bi2S3. The specific capacitance of Bi2O3@1 g PVP is 1.4 times that of the pristine Bi2O3, and the specific capacitance of Bi2S3@1 g PVP is 1.8 times that of the pristine Bi2S3. Compared with 82.0% Bi2O3 and 79.6% Bi2S3, the cyclic retention is 94.7% and 95.2% for Bi2O3@1 g PVP and Bi2S3@1 g PVP after 10,000 cycles. The reason for enhancement is that PVP can support Bi2O3 and Bi2S3 materials, not only to support their structural stability but also to reduce their size and facilitate electron transfer and ion diffusion.

Automated summary

In this study, Bi2O3 and Bi2S3 nanomaterials were modified with polyvinylpyrrolidone (PVP) to form Bi2O3@PVP and Bi2S3@PVP. The addition of PVP reduced the size of Bi2O3 and Bi2S3 nanomaterials, changed the structure of Bi2O3, and induced reduction of trivalent Bi3+. PVP improved the capacitive performance and cyclic stability of both Bi2O3 and Bi2S3 through supporting their structural stability, reducing their size, and facilitating electron transfer and ion diffusion.