美国宾夕法尼亚大学Thomas E. Mallouk研究组开发出了一种可提高二氧化碳电解效率的含弱酸性阳离子交换层的双极膜。该项研究成果发表在2020年12月7日出版的《自然·化学》上。

在该文中，研究人员在膜电解池中成功实现了在数十纳米的尺度上测量和调节局部pH。在基于双极膜的通气CO₂电解池中，阳离子交换层的酸性环境会导致CO₂还原效率降低。通过比例指示剂和聚电解质的层层自组装，研究人员实现了对约50纳米厚的弱酸层的测量和控制。这一弱酸层抑制了竞争性的析氢反应，同时不影响CO₂还原。

这一探测和控制局部膜环境的方法可能在诸如电解池、燃料电池和液流电池等装置中得到应用，同时也为在聚合物电解质中实时原位研究离子分布提供了新方法。

据了解，将电力高效转化为化学物质对解决可再生能量来源的不连续问题至关重要。推动这些电化学反应以实用化的速率运行不仅需要较快的电极动力学，也需要较快的传质和离子传导。然而，人们对固体电解质中局部环境对离子传导的影响知之甚少。

附：英文原文

Title: Improving the efficiency of CO 2 electrolysis by using a bipolar membrane with a weak-acid cation exchange layer

Author: Zhifei Yan, Jeremy L. Hitt, Zichen Zeng, Michael A. Hickner, Thomas E. Mallouk

Issue&Volume: 2020-12-07

Abstract: The efficient conversion of electricity to chemicals is needed to mitigate the intermittency of renewable energy sources. Driving these electrochemical conversions at useful rates requires not only fast electrode kinetics, but also rapid mass and ion transport. However, little is known about the effect of local environments on ionic flows in solid polymer electrolytes. Here, we show that it is possible to measure and manipulate the local pH in membrane electrolysers with a resolution of tens of nanometres. In bipolar-membrane-based gas-fed CO2 electrolysers, the acidic environment of the cation exchange layer results in low CO2 reduction efficiency. By using ratiometric indicators and layer-by-layer polyelectrolyte assembly, the local pH was measured and controlled within an ~50-nm-thick weak-acid layer. The weak-acid layer suppressed the competing hydrogen evolution reaction without affecting CO2 reduction. This method of probing and controlling the local membrane environment may be useful in devices such as electrolysers, fuel cells and flow batteries, as well as in operando studies of ion distributions within polymer electrolytes.

DOI: 10.1038/s41557-020-00602-0

Source: https://www.nature.com/articles/s41557-020-00602-0