Alkali metal cations enhance CO₂ reduction by a Co molecular complex in a bipolar membrane electrolyzer

Siritanaratkul, Bhavin ORCID: 0000-0003-0604-7670, Khan, Mohammad Danish, Yu, Eileen H and Cowan, Alexander J ORCID: 0000-0001-9032-3548 (2024) Alkali metal cations enhance CO₂ reduction by a Co molecular complex in a bipolar membrane electrolyzer PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, 382 (2282). 20230268-. ISSN 1364-503X, 1471-2962

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Abstract

The electrochemical reduction of CO 2 is a promising pathway for converting CO 2 into valuable fuels and chemicals. The local environment at the cathode of CO 2 electrolyzers plays a key role in determining activity and selectivity, but currently some mechanisms are still under debate. In particular, alkali metal cations have been shown to enhance the selectivity of metal catalysts, but their role remains less explored for molecular catalysts especially in high-current electrolyzers. Here, we investigated the enhancement effects of cations (Na +, K +, Cs +) on Co phthalocyanine (CoPc) in a state-of-the-art reverse-biased bipolar membrane electrolyzer. When added to the anolyte, these cations increased the Faradaic efficiency for CO, except in the case of Na + in which the effect was transient, but the effects are convoluted with the transport process through the membrane. Alternatively, these cations can also be added directly to the cathode as chloride salts, allowing the use of a pure H 2 O anolyte feed, leading to sustained improved CO selectivity (61% at 100 mA cm -2 after 24 h). Our results show that cation addition is a simple yet effective strategy for improving the product selectivity of molecular electrocatalysts, opening up new avenues for tuning their local environment for CO 2 reduction. This article is part of the discussion meeting issue 'Green carbon for the chemical industry of the future'.

Item Type:	Article
Uncontrolled Keywords:	carbon dioxide reduction, bipolar membrane, zero-gap electrolyzer, molecular catalyst, cation
Divisions:	Faculty of Science & Engineering > School of Physical Sciences
Depositing User:	Symplectic Admin
Date Deposited:	13 May 2024 08:04
Last Modified:	16 Jun 2026 20:05
DOI:	10.1098/rsta.2023.0268
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3180878
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