The role of an interface in stabilizing reaction intermediates for hydrogen evolution in aprotic electrolytes,Chemical Science

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The role of an interface in stabilizing reaction intermediates for hydrogen evolution in aprotic electrolytes
Chemical Science ( IF 7.6 ) Pub Date : 2020-03-24 , DOI: 10.1039/c9sc05768d
Ivano E. Castelli _{1,

2,

3,

4,

5} , Milena Zorko _{6,

7,

8,

9} , Thomas M. Østergaard _{1,

2,

3,

4,

5} , Pedro F. B. D. Martins _{6,

7,

8,

9} , Pietro P. Lopes _{6,

7,

8,

9} , Byron K. Antonopoulos _{10,

11,

12,

13} , Filippo Maglia _{10,

11,

12,

13,

14} , Nenad M. Markovic _{6,

7,

8,

9} , Dusan Strmcnik _{6,

7,

8,

9} , Jan Rossmeisl _{1,

2,

3,

4,

5}

Affiliation

By combining idealized experiments with realistic quantum mechanical simulations of an interface, we investigate electro-reduction reactions of HF, water and methanesulfonic acid (MSA) on the single crystal (111) facets of Au, Pt, Ir and Cu in organic aprotic electrolytes, 1 M LiPF₆ in EC/EMC 3:7W (LP57), the aprotic electrolyte commonly used in Li-ion batteries, 1 M LiClO₄ in EC/EMC 3:7W and 0.2 M TBAPF₆ in 3 : 7 EC/EMC. In our previous work, we have established that LiF formation, accompanied by H₂ evolution, is caused by a reduction of HF impurities and requires the presence of Li at the interface, which catalyzes the HF dissociation. In the present paper, we find that the measured potential of the electrochemical response for these reduction reactions correlates with the work function of the electrode surfaces and that the work function determines the potential for Li⁺ adsorption. The reaction path is investigated further by electrochemical simulations suggesting that the overpotential of the reaction is related to stabilizing the active structure of the interface having adsorbed Li⁺. Li⁺ is needed to facilitate the dissociation of HF which is the source of protons. Further experiments on other proton sources, water and methanesulfonic acid, show that if the hydrogen evolution involves negatively charged intermediates, F⁻ or HO⁻, a cation at the interface can stabilize them and facilitate the reaction kinetics. When the proton source is already significantly dissociated (in the case of a strong acid), there is no negatively charged intermediate and thus the hydrogen evolution can proceed at much lower overpotentials. This reveals a situation where the overpotential for electrocatalysis is related to stabilizing the active structure of the interface, facilitating the reaction rather than providing the reaction energy.

中文翻译：

界面在非质子电解质中稳定氢生成反应中间体的作用

通过将理想化实验与界面的逼真的量子力学模拟相结合，我们研究了HF，水和甲磺酸（MSA）在有机质子惰性电解质中Au，Pt，Ir和Cu的单晶（111）晶面上的电还原反应，EC / EMC 3：7W（LP57）中的1 M LiPF ₆（锂离子电池中常用的非质子电解质），EC / EMC 3：7W中的1 M LiClO ₄和3：7 EC / EMC中的0.2 M TBAPF ₆。在我们之前的工作中，我们确定了LiF的形成以及H _2的伴随析出是由于HF杂质减少所致，并且需要在界面处存在Li，从而催化HF分解。在本文中，我们发现这些还原反应的电化学反应电势与电极表面的功函数相关，而功函数决定了Li ⁺吸附的电势。通过电化学模拟进一步研究了反应路径，表明反应的超电势与稳定已吸附Li ⁺的界面的活性结构有关。李⁺需要促进HF的解离，HF是质子的来源。其它质子源，水和甲磺酸，显示的是，如果氢生成包括带负电荷的中间体，F进一步的实验^-或HO ^-，在界面处的阳离子能稳定它们并促进反应动力学。当质子源已经显着分解（在强酸的情况下）时，不存在带负电荷的中间体，因此氢的释放可以在低得多的超电势下进行。这揭示了电催化的过电位与稳定界面的活性结构，促进反应而不是提供反应能量有关的情况。

更新日期：2020-04-24

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