限制空間導引之氫氣生成反應

Abstract

氫氣是重要的乾淨能源，電解水為產生氫氣的方法之一，目前大多數研究集中在通過合成新材料或改變材料表面化學組成來尋找能取代貴金屬的高效氫氣生成反應 (Hydrogen Evolution Reaction, HER) 的電催化劑而我們則探索了通過改變材料的幾何結構來提高催化性能。我們利用表面力儀（Surface Force Apparatus, SFA）在金和雲母表面之間創建奈米至微米級的限制空間，觀察並分析在此條件下導引的HER催化現象。通過遷移、對流和擴散等機制來研究水合氫離子在限制空間中的質量傳輸過程，並使用Comsol多物理場建模和原位影像分析等方法來深入理解這些作用。研究顯示，限制空間會提高電極表面電位並促使水合氫離子遷移。氣泡的形成會撐開限制空間，提供水合氫離子運輸通道並引發微對流，加速電解質進入間隙。雲母表面的高水合氫離子濃度使水合氫離子從雙電層擴散到金表面，增強水合氫離子傳輸。但這些短程作用無法完全解釋催化能力，暗示存在長程相互作用。本研究證明，通過改變材料的幾何結構而非表面組成，可以有效提升HER催化性能，並以質量傳輸的角度為此現象提供了解釋。

Hydrogen is an important clean energy source, and water electrolysis is one of the methods for producing hydrogen. Currently, most research focuses on finding efficient electrocatalysts for the hydrogen evolution reaction (HER) that can replace precious metals by synthesizing new materials or altering the chemical composition of material surfaces. In our study, we explored enhancing catalytic performance by changing the geometric structure of the materials. We used a Surface Force Apparatus (SFA) to create nanometer to micrometer-scale confined spaces between gold and mica surfaces, observing and analyzing the HER catalytic phenomena under these conditions. We investigated the mass transport processes of hydronium ion in confined spaces through mechanisms such as migration, convection, and diffusion, and used Comsol multiphysics modeling and in-situ imaging analysis to gain a deeper understanding of these effects. Our research showed that confined spaces increase the electrode surface potential and promote the migration of hydronium ion. The formation of bubbles expands the confined spaces, providing channels for the transport of hydronium ion and inducing micro-convection, which accelerates the entry of electrolytes into the gaps. The high concentration of hydronium ion on the mica surface enhances the diffusion of these ions from the electric double layer of mica to the gold surface, improving ion transport. However, these short-range effects do not fully explain the catalytic capability, suggesting the presence of long-range interactions. This study demonstrates that altering the geometric structure of materials, rather than their surface composition, can effectively enhance HER catalytic performance, providing an explanation for this phenomenon from the perspective of mass transport.