Goyal Akansha, Louisia Sheena, Moerland Pricilla, Koper Marc T M
Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
J Am Chem Soc. 2024 Mar 20;146(11):7305-7312. doi: 10.1021/jacs.3c11866. Epub 2024 Mar 7.
The kinetics of hydrogen evolution reaction (HER) in alkaline media, a reaction central to alkaline water electrolyzers, is not accurately captured by traditional adsorption-based activity descriptors. As a result, the exact mechanism and the main driving force for the water reduction or HER rate remain hotly debated. Here, we perform extensive kinetic measurements on the pH- and cation-dependent HER rate on Pt single-crystal electrodes in alkaline conditions. We find that cations interacting with Pt step sites control the HER activity, while they interact only weakly with Pt(111) and Pt(100) terraces and, therefore, cations do not affect HER kinetics on terrace sites. This is reflected by divergent activity trends as a function of pH as well as cation concentration on stepped Pt surfaces vs Pt surfaces that do not feature steps, such as Pt(111). We show that HER activity can be optimized by rationally tuning these step-cation interactions via selective adatom deposition at the steps and by choosing an optimal electrolyte composition. Our work shows that the catalyst and the electrolyte must be tailored in conjunction to achieve the highest possible HER activity.
碱性介质中析氢反应（HER）的动力学是碱性水电解槽的核心反应，传统的基于吸附的活性描述符无法准确捕捉该反应的动力学。因此，析氢反应中析氢速率的具体机制和主要驱动力仍然存在激烈争议。在此，我们对碱性条件下铂单晶电极上pH值和阳离子依赖性析氢速率进行了广泛的动力学测量。我们发现，与铂台阶位点相互作用的阳离子控制着析氢活性，而它们与铂（111）和铂（100）平台的相互作用较弱，因此，阳离子不会影响平台位点上的析氢动力学。这表现为在有台阶的铂表面与没有台阶的铂表面（如铂（111））上，析氢活性随pH值和阳离子浓度的变化趋势不同。我们表明，通过在台阶处选择性地沉积吸附原子以及选择最佳的电解质组成，合理调节这些台阶 - 阳离子相互作用，可以优化析氢活性。我们的工作表明，必须同时对催化剂和电解质进行定制，以实现尽可能高的析氢活性。
