Tan, Yeshu; (2023) Platinum-based Self-standing Electrocatalysts for Efficient Hydrogen Evolution Reaction. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The hydrogen evolution reaction (HER) requires stable and effective platinum (Pt)-based electrocatalysts. Traditional Pt powdery electrocatalysts face problems of dispersion and dissolution during the electrode preparation process and HER process. This leads to poor durability under high current density, especially if aiming for future industrial applications. Thus, platinum-based self-standing electrocatalysts were developed in this thesis for efficient and durable HER. Furthermore, traditional platinum-based electrocatalysts have limitations in HER activity in neutral and alkaline medium due to sluggish water dissociation, limited diffusion of H⁺ and slow desorption of H*. Therefore, based on selected substrates, Pt nanocrystals were grown directly on substrate as self-standing electrocatalyst, exploring the tuning of electronic structure in both experimental and theoretical results. First, Pt nanocrystals in the form of "blackberries" on copper (Cu) foams with minimal loading served as a self-standing electrode and the synthesis was accomplished by an easy, low-temperature strategy. The interaction between Pt and Cu foam was studied, leading to materials with ultra-stability under high current density. Second, based on the interaction between Pt and Cu, phosphorus was introduced to modify the surface environment, further increasing the HER performance in neutral medium. Third, Ni₂P/CoP nanosheet was grown directly on nickel (Ni) foam, which was considered as an efficient self-standing electrocatalyst. The synergistic effect was explored between Ni₂P and CoP. Furthermore, the as-prepared electrocatalyst was applied to domestic wastewater for HER, widening the feasibility of HER in complicated electrolytes. Fourth, Pt nanocrystals were grown on the edge of the Ni₂P/CoP nanosheet, forming a unique heterostructure, as a self-standing electrocatalyst. The local electric field effect and electronic structure were both explored, illustrating the remarkable HER activity in alkaline medium. This thesis described the modification of Pt nanocrystals on selected substrates as self-standing electrocatalyst for efficient and stable HER process.

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