Feeding silkworms with HPMC dispersed MoO2 NPs: An efficient strategy to enhance the supercapacitance performance of carbonized silk

Abstract It was found in our previous study that feeding silkworms with MoO2 nanoparticles (NPs) as a food additive enabled the incorporation of MoO2 NPs into the as-spun silk, which, in turn, can be used to build electrodes for energy storage. However, aggregation of the MoO2 NPs was observed at high fractional feeding dosages. In order to disperse the MoO2 NPs in fibrous silk and enhance the specific capacitance of the carbonized silk more effectively, a 0.5% (w/v) hydroxypropyl methyl cellulose (HPMC) solution was utilized as the dispersant in this work. Transmission electron microscopy (TEM) results confirmed that HPMC increased the separation of MoO2 nanoparticles incorporated within the silk matrix. Furthermore, the electrochemical performance was characterized, revealing that the specific capacitance of carbonized silk from this HPMC-MoO2 NP feeding group reached 456 F/g, compared to the value of 245 F/g from the previous study, at a current density of 0.2 A/g, demonstrating a significant improvement. The feasibility of utilizing HPMC to maintain the segregated state of MoO2 NPs throughout all stages of silk encapsulation, with negligible impact of this feeding regimen on the growth of silkworms, is demonstrated in this work.