The role of alkali metal cations and platinum-surface hydroxyl in the alkaline hydrogen evolution reaction
The role of alkali metal cations and platinum-surface hydroxyl in the alkaline hydrogen evolution reaction
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DOI：
10.1038/s41929-022-00851-x
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发表时间：
2022-10-19
期刊：
影响因子：
37.8
通讯作者：
Duan, Xiangfeng
中科院分区：
文献类型：
--
作者：
Shah, Aamir Hassan;Zhang, Zisheng;Duan, Xiangfeng
铂催化的析氢反应（HER）通常在碱性电解质中显示较差的动力学，并且代表碱性水电解的关键挑战。在碱金属阳离子和羟基阴离子的存在下，碱性电解质中的电极-电解质（铂-水）界面远比酸性电解质中的复杂。在这里，我们结合联合收割机电化学阻抗谱和电传输光谱的方法来探测和理解不同的阳离子（Li+，Na+和K+）在HER动力学的基本作用。我们的综合研究表明，碱金属阳离子在修改HER动力学中起间接作用，较小的阳离子在HER电位窗口中对羟基吸附物（OHad）物种的不稳定性较小，这有利于OHad在铂表面上的更高覆盖率。表面OHad物种是高度极性的，并且充当电子上有利的质子受体和几何上有利的质子供体以促进碱性介质中的水解离，从而提高Volmer-步骤动力学和HER活性。
The platinum-catalysed hydrogen evolution reaction (HER) generally shows poorer kinetics in alkaline electrolyte and represents a key challenge for alkaline water electrolysis. In the presence of alkali metal cations and hydroxyl anions, the electrode-electrolyte (platinum-water) interface in an alkaline electrolyte is far more complex than that in an acidic electrolyte. Here we combine electrochemical impedance spectroscopy and an electrical transport spectroscopy approach to probe and understand the fundamental role of different cations (Li+, Na+ and K+) in HER kinetics. Our integrated studies suggest that the alkali metal cations play an indirect role in modifying the HER kinetics, with the smaller cations being less destabilizing to the hydroxyl adsorbate (OHad) species in the HER potential window, which favours a higher coverage of OHad on the platinum surface. The surface OHad species are highly polar and act as both electronically favoured proton acceptors and geometrically favoured proton donors to promote water dissociation in alkaline media, thus boosting the Volmer-step kinetics and the HER activity.