Synthesis of multi-component electrocatalysts and electrode materials via chemical vapor deposition and their applications

Abstract

For high performance of proton exchange membrane fuel cells (PEMFCs) and efficient hydrogen generation by water electrolysis, Pt based multi-metallic nanoparticles and carbon-metal hybrid nanoparticles have been suggested as promising candidate cathode catalysts for the oxygen reduction reaction (ORR) and the hydrogen evolution reaction (HER), respectively. Unfortunately, the difficulty in controlling the nanoscale particle size and the precise composition, as well as the multistep labor-intensive synthetic processes, have been significant limiting factors for the practical employment of multi-component nanoparticles in electrocatlysts and electrode materials fields. In this dissertation, A facile synthetic process for multi-component electrocatalysts and electrode materials via one-pot sequential and simultaneous chemical vapor deposition (CVD) is demonstrated. In the chapter 2, the deposition mechanisms of Pt and Co were investigated and the highly monodisperse Pt-Co alloy nanoparticles with precise control of metallic compositions within 1 at% were successfully developed. Furthermore, perfectly alloyed single crystal structure was obtained at as low as 500 °C, which is much lower than conventional alloying temperatures (700-900 °C). In the chapter 3, the graphene encapsulated CoP, CoS$_2$ and Co$_3$O$_4$ nanoparticles were successfully synthesized with facile and simple CVD and following post treatments. Furthermore, the graphene encapsulated CoP shows high activity and stability for HER and graphene encapsulated Co$_3$O$_4$ shows excellent long-term stability for Li-ion battery anode materials. I would like to emphasize that our sequential or simultaneous, one-pot CVD synthetic method is a general technique, and readily transferable to the synthesis of further custom mutli-component nanocatalysts systems for inorganic-inorganic hybrids and organic-inorganic hybrids. Our new technique therefore opens up the possibility of generalized synthesis for a diverse range of multi-component nanocatalysts and electrode materials.