Synthesis Of Nanocomposites Via Bacterial Template And Electrostatic Spray Deposition Method And Their Applications

Recently, given the increasing threats to the world’s collective energy security and environment security,more attention has been focused towards addressing these challenges and driving global research to develop new material and technology for energy storage and high performance sensors. The demand for high performance materials has led to increasing attention in advanced functional nanocomposites.Although nanocomposites have been demonstrated to behave excellent performance,their research is still limited at laboratory-level, preparing nanocomposites with low-cost and large-scale is still a big problem. Improving the preparation process and using cheap raw materials is of great importance to control the structure and cost of the product. In this paper, nanocomposites with unique structure and good performance were synthesized through low-cost bio-template method（bacteria template method） and scalable electrostatic spray deposition（ESD） technology, their potential applications in gas sensors and supercapacitors were also studied. The main contents are summarized in the following:（1）Co₃O₄ decorated ZnO hollow spheres were synthesized by a bacterial template method, the weight percentage of Co₃O₄ was about 4%. The Co₃O₄ decorated ZnO hollow spheres resembled the morphology of the bacterial templates with multilayered porous shells. The shell was piled up with ZnO nanograins of about 20 nm and the thickness of the shell was about 100 nm. Their sensing properties were tested, compared to pure ZnO hollow spheres, Co₃O₄ decorated ZnO nanocomposites behaved higher and faster response to acetone. Their excellent properties were contributed to the unique porous hollow structure as well as the formation of p-n junction.（2）We used an one-step electrostatic spray deposition strategy to fabricate the electrode, a mixed solution of nickel acetate and GO was directly deposited onto heated current collector. GO was reduced to rGO and nickel acetate was decomposed to NiO nanograins anchored on rGO sheets. The electrode showed excellent supercapacitor performance due to its novel structure. The binder-free nature of the electrode resulted in a direct contact of composite film with nickel foam substrate,most of the NiO nanograins in the macroscopic ensemble were electrochemically active through the layered graphene network.（3）A flexible electrode based on Mn₃O₄/rGO composites was fabricatedthrough a two-step strategy. Firstly, Mn₃O₄ nanoflower was synthesized through the reduction of KMn O4, then, a mixed solution of Mn₃O₄ and GO was electrostatic spray deposited onto heated carbon cloth, during the deposition process, GO was reduced to rGO. The flexible electrode prepared by electrostatic spray deposition（GM） showed better supercapacitor performance than the electrode prepared by traditional slurry coating method（CG）. GM maintained an intimate contact between active material and current collector, even at a fully bending state. On the contrary, the active material on CG may lose contact with current collector when bending and leading to capacity loss.（4）The Bacillus subtilis promoted porous nickel sulfide-reduced graphene oxide composites directly supported on nickel foam was realized by two-step electrostatic spray deposition approach. Ni₃S₂ nanoparticles（¹0 nm） are uniformly anchored onto reduced graphene oxide sheets with submillimeter pores, resulting in an intimate contact between the nanoparticles and reduced graphene oxide sheets,which afforded a facile electron transport in the composite. The structure promoted by bacteria severed as a robust reservoir for ions, which greatly improved the diffusion kinetics within the electrode. The binder-free nature of the electrode resulted in a direct contact of the conductive composites film with nickel foam substrate, most of the Ni₃S₂ nanoparticles in the macroscopic ensemble were electrochemically active through the network.