An electrochemical investigation of oxygen adsorption on Pt single crystal electrodes in a non-aqueous Li+ electrolyte
An electrochemical investigation of oxygen adsorption on Pt single crystal electrodes in a non-aqueous Li+ electrolyte
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DOI：
10.1016/j.elecom.2020.106814
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发表时间：
2020-10
影响因子：
5.4
通讯作者：
Thomas A. Galloway;G. Attard;L. Hardwick
中科院分区：
文献类型：
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作者：
Thomas A. Galloway;G. Attard;L. Hardwick
循环伏安法已被用来探测含锂二甲亚砜中的氧还原和氧化的初始阶段，在定义良好的Pt单晶电极，以阐明任何催化作用归因于表面结构。与以前涉及钠-氧的工作相反，锂-氧研究在铂的三个基面上的反应没有产生任何显着差异。相反，所有三个平面产生类似的伏安响应。然而，通过明智地使用各种潜在的扫描限制，形成的超氧化物与“保形”或表面吸附层的过氧化锂（Li 2 O2）与“微晶”表面Li 2 O2相一起解决。伏安峰强度与扫描速率的测量结果证实，超氧化物电氧化扩散限制，而两个Li 2 O2相的电氧化显示的行为典型的表面限制的过程。在稳态条件下形成的超氧化物，有人发现，对于共形和微晶Li 2 O2相，电氧化遵循零级动力学，自由表面位点在促进这些反应的重要性。发现Li 2 O2形成速率的显著变化与0.25单层的覆盖率一致，如通过保形Li 2 O2电氧化峰的电荷密度所测量的。我们假设电子隧道穿过保形Li 2 O2层和沉积在该表面层上的微晶与这种覆盖范围一致，并解释了这种行为。通过单一的共形和混合共形/微晶结构的电子隧穿的这种现象应证明是至关重要的，在管理的整体电氧化速率。
Cyclic voltammetry has been used to probe the initial stages of oxygen reduction and oxidation in lithium-containing dimethyl sulfoxide at well-defined Pt single crystal electrodes in order to elucidate any catalytic effects ascribable to surface structure. In contrast to previous work involving sodium-oxygen, lithium-oxygen studies did not yield any significant differences for reaction on the three basal planes of platinum. Rather, all three planes generated a similar voltammetric response. However, by judicious use of various potential sweep limits, the formation of superoxide together with both a “conformal” or surface adlayer of lithium peroxide (Li2O2) together with a “microcrystallite” surface Li2O2phase was resolved. Voltammetric peak intensity versus sweep rate measurements confirmed that superoxide electrooxidation was diffusion limited whereas electrooxidation of the two Li2O2phases displayed behaviour typical of a surface-confined process. Under steady-state conditions for the formation of superoxide, it was found that for both the conformal and microcrystallite Li2O2phases, electrooxidation followed zero-order kinetics, pointing to the importance of free surface sites in facilitating these reactions. A marked change in the rate of Li2O2formation was found to coincide with a coverage of 0.25 monolayers, as measured by the charge density of the conformal Li2O2electrooxidation peak. We postulate that electron tunnelling through both the conformal Li2O2layer and microcrystallites deposited on this surface layer coincides with this coverage and accounts for such behaviour. This phenomenon of electron tunnelling through single conformal and mixed conformal/microcrystallite structures should prove vitally important in governing the overall electrooxidation rate.