Operando Local pH Measurement within Gas Diffusion Electrodes Performing Electrochemical Carbon Dioxide Reduction,The Journal of Physical Chemistry C

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Operando Local pH Measurement within Gas Diffusion Electrodes Performing Electrochemical Carbon Dioxide Reduction
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2021-09-17 , DOI: 10.1021/acs.jpcc.1c06265
Alex J. Welch _{1,

2} , Aidan Q. Fenwick _{2,

3} , Annette Böhme _{1,

2} , Hsiang-Yun Chen ₃ , Ian Sullivan ₂ , Xueqian Li _{1,

2} , Joseph S. DuChene ₄ , Chengxiang Xiang ₂ , Harry A. Atwater _{1,

2}

Affiliation

The local pH near the surface of a CO₂ reduction electrocatalyst strongly impacts catalytic selectivity and activity. Here, confocal fluorescence microscopy was used to map the electrolyte pH near a copper gas diffusion electrode during CO₂ reduction with micron spatial resolution in three dimensions. We observed that the local pH increased from pH 6.8 to greater than pH 10 as the current density was increased from 0 to 28 mA/cm² in a 100 mM KHCO₃ electrolyte. Variations in the pH across the surface indicate areas of locally increased activity. Within deep trenches of the active layer, the local pH increases as trench width decreases. Computational models confirm these experimental results and also showed that the catalyst found within narrow trenches is more active than that found at the surface of the electrode. This study suggests that the overpotential required to perform selective CO₂ reduction can be reduced by increasing the density of narrow trench regions in the microporous layer.

中文翻译：

在进行电化学二氧化碳还原的气体扩散电极中进行操作数局部 pH 测量

CO ₂还原电催化剂表面附近的局部pH强烈影响催化选择性和活性。在这里，共聚焦荧光显微镜用于在三个维度上以微米空间分辨率绘制 CO ₂还原过程中铜气体扩散电极附近的电解质 pH 值。我们观察到，在 100 mM KHCO _{3 中}，随着电流密度从 0 增加到 28 mA/cm ²，局部 pH 从 pH 6.8 增加到大于 pH 10电解质。整个表面 pH 值的变化表明局部活性增加的区域。在有源层的深沟槽内，局部 pH 值随着沟槽宽度的减小而增加。计算模型证实了这些实验结果，并且还表明在狭窄沟槽内发现的催化剂比在电极表面发现的催化剂更活跃。该研究表明，可以通过增加微孔层中窄沟槽区域的密度来降低执行选择性 CO ₂还原所需的过电位。

更新日期：2021-09-30

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