Ultrathin silica mesh protected Pt nanoparticles for hydrogen evolution reaction (HER)

• Main Author: Hung, Hsi Chien
• Other Authors: Liu Zheng
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Materials::Nanostructured materials
• Online Access: https://hdl.handle.net/10356/147790
• Institution: Nanyang Technological University

Hydrogen evolution reaction (HER) is the fundamental half-reaction involved in hydrogen gas production. HER is a cathodic reaction in electrolysis, where proton is converted into H2 gas with the help of a electrocatalyst. Platinum (Pt)-based catalysts are known to be the most effective catalysts for HER. In this study, Graphene-Pt-SiO2 electrocatalyst is fabricated by encapsulating graphene-supported Pt nanoparticles with ultrathin mesoporous silica mesh with thicknesses ranging from 0.1 to 10 nm. AFM images showed that the aggregation issue of Pt nanoparticles is greatly suppressed by the mesoporous silica layer. Tafel slopes corresponding to HER in 0.5 M H2SO4 solution are decreased from 86 to 58 mV dec−1 when the silica thickness is reduced from 2.0nm to 0.2nm, revealing that thinner silica coatings resulted in better catalytic activities. The remarkable catalytic stability and activity can be attributed to porous network of the SiO2 layers, which not only prevented Pt from sintering during HER, but also allowed reactant molecules to be transported through its pores easily to reach the active catalytic sites on encapsulated Pt nanoparticles. Importantly, 0.2nm and 0.6nm SiO2-encapsulated electrocatalysts were found to have the best HER activities, with a Tafel slope of 58 and 57 mV dec−1 respectively. Fundamental insights into HER reaction mechanism are discussed. The 2 main strategies commonly employed for the improvement of catalytic performance and stability based on (1) core-shell configuration and (2) encapsulation by mesoporous layer are also described in the literature review. The enhanced electrochemical properties for Pt-based nanoparticles opened doors to a more cost-efficient and stable electrocatalyst for the promotion of hydrogen economy in the future.