武汉大学陈胜利团队报道了由普遍的氢氧化物吸附依赖拐点行为揭示氢电催化动力学pH效应的双电层起源。相关研究成果发表在2023年5月23日出版的国际学术期刊《美国化学会杂志》。

氢电催化中动力学pH效应的机制，即酸性和碱性电解质中氢氧化和析氢反应（HOR/HER）之间的数量级动力学间隙，已经得到了深入的探索，但仍难以达成共识，这严重限制了碱性氢能技术的催化剂进展。

该文中，在pH范围从1到13的电解质中评估了许多贵金属基电催化剂上的HOR/HER动力学。与通常认为的随pH单调下降不同，研究人员出人意料地发现，在这些催化剂上HOR/HER动力学的pH依赖性中存在普遍的拐点行为，拐点pH和酸碱活性间隙都取决于催化剂的氢氧化物结合能。

基于三路径微动力学模型，其中水合氢（H₃O⁺）和水（H₂O）在形成和不形成吸附的氢氧化物（OHad）的情况下分别作为氢供体参与不同pH下的HOR/HER，研究人员揭示了OHad的形成应主要通过改善双电层（EDL）中的氢键网络来促进HOR/HER的动力学，而不是仅仅通过调节表面反应步骤的能量学，例如水的离解/形成。目前的结果和结论表明，正是界面EDL主导了氢电催化的基本动力学pH效应。

附：英文原文

Title: Electric-Double-Layer Origin of the Kinetic pH Effect of Hydrogen Electrocatalysis Revealed by a Universal Hydroxide Adsorption-Dependent Inflection-Point Behavior

Author: Lixin Su, Junxiang Chen, Fulin Yang, Peng Li, Yiming Jin, Wei Luo, Shengli Chen

Issue&Volume: May 23, 2023

Abstract: The mechanism of the kinetic pH effect in hydrogen electrocatalysis, that is, the order-of-magnitude kinetic gap between the hydrogen oxidation and evolution reactions (HOR/HER) in acidic and alkaline electrolytes, has been drastically explored but still intractable to reach a consensus, which severely limits the catalyst advance for alkaline-based hydrogen energy technologies. Herein, the HOR/HER kinetics on a number of precious metal-based electrocatalysts are evaluated in electrolytes with pHs spanning a wide range from 1 to 13. Instead of a monotonous decrease with pH as generally believed, we surprisingly find a universal inflection-point behavior in the pH dependence of HOR/HER kinetics on these catalysts, with both the inflection-point pH and the acid-alkaline activity gap depending on the hydroxide binding energy of the catalyst. Based on a triple-path microkinetic model, in which hydronium (H3O+) and water (H2O) with and without formation of adsorbed hydroxide (OHad), respectively, act as hydrogen donors participating in HOR/HER in various pHs, we reveal that the formation of OHad should promote the HOR/HER kinetics mainly by improving the hydrogen-bond network in the electric double layer (EDL), rather than merely through modulating the energetics of surface reaction steps such as disassociation/formation of water. The present results and conclusions indicate that it is the interfacial EDL that dominates the substantial kinetic pH effects of hydrogen electrocatalysis.

DOI: 10.1021/jacs.3c01164

Source: https://pubs.acs.org/doi/10.1021/jacs.3c01164