Li Peng, Jiang Ya-Ling, Men Yana, Jiao Yu-Zhou, Chen Shengli
Hubei Key Laboratory of Electrochemical Power Sources, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, China.
Nat Commun. 2025 Feb 21;16(1):1844. doi: 10.1038/s41467-025-56966-9.
Unveiling the so far ambiguous mechanism of the significant dependence on the identity of alkali metal cation would prompt opportunities to solve the more than two orders of magnitude slowdown of hydrogen electrocatalytic kinetics in base relative to acid, which has hampered the effort to reduce the precious metal usage in fuel cells by using the hydroxide exchange membrane. Herein, we present atomic-scale evidences from ab-initio molecular dynamics simulation and in-situ surface-enhanced infrared absorption spectroscopy which show that it is the apparent discrepancies in the electric double-layer structures induced by differently sized cations that lead to largely different interfacial proton transfer barriers and therefore hydrogen electrocatalytic kinetics in base. Concretely, severe accumulation of larger cation in electric double-layer causes more discontinuous interfacial water distribution and H-bond network, thus rendering the proton transfer from bulk to interface more obstructed. Such notion is strikingly different from the previously envisioned impact of cation-intermediate interactions on the energetics of surface steps, providing a unique interfacial perspective for understanding the ubiquitous cation specificity in electrocatalysis.
揭示到目前为止尚不明确的对碱金属阳离子身份有显著依赖性的机制，将为解决碱性条件下氢电催化动力学相对于酸性条件减慢两个多数量级的问题带来契机，这一问题一直阻碍着通过使用氢氧化物交换膜来减少燃料电池中贵金属用量的努力。在此，我们展示了来自从头算分子动力学模拟和原位表面增强红外吸收光谱的原子尺度证据，这些证据表明，不同大小阳离子引起的双电层结构的明显差异导致了截然不同的界面质子转移势垒，从而导致了碱性条件下的氢电催化动力学。具体而言，较大阳离子在双电层中的严重积累导致界面水分布和氢键网络更加不连续，从而使质子从本体转移到界面更加受阻。这种观点与之前所设想的阳离子-中间体相互作用对表面台阶能量的影响截然不同，为理解电催化中普遍存在的阳离子特异性提供了独特的界面视角。
