Wu Bo, Wang Bingqing, Cai Beijing, Wu Chao, Tjiu Weng Weei, Zhang Mingsheng, Aabdin Zainul, Xi Shibo, Lum Yanwei
Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117585, Republic of Singapore.
Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore.
J Am Chem Soc. 2024 Oct 30;146(43):29801-29809. doi: 10.1021/jacs.4c11564. Epub 2024 Sep 12.
Electrochemical CO reduction (COR) in acidic media provides a pathway to curtail CO losses by suppressing the formation of (bi)carbonates. In such systems, a high concentration of alkali metal cations is necessary for mitigating the proton-rich environment and suppressing the competing hydrogen evolution reaction. However, a high cation concentration also promotes salt precipitation within the gas diffusion layer, resulting in poor system durability. Here, we resolve this conundrum by replacing the liquid catholyte with a solid-state proton conductor to regulate H transport. This is postulated to allow for a locally alkaline environment at the cathode, enabling selective COR even without alkali metal cations. We show that this strategy is effective over a broad range of catalyst systems. For instance, we achieve an 87% CO faradaic efficiency (FE) at 300 mA/cm using a composite nanoporous Au and single-atom Ni catalyst, with 0.25 M HSO as the anolyte. Stable operation over 110 h and a high single-pass carbon efficiency of 82.8% were also successfully demonstrated. Importantly, we find that this solid-state system is also particularly effective at converting dilute feedstock (5% CO) with a CO FE of 47.7%, a factor of 16.4 times higher than a conventional system. Our results introduce a simple yet effective design approach for developing efficient acidic COR electrolyzers.
酸性介质中的电化学CO还原（COR）提供了一条通过抑制（双）碳酸盐的形成来减少CO损失的途径。在这样的系统中，高浓度的碱金属阳离子对于缓解富质子环境和抑制竞争性析氢反应是必要的。然而，高阳离子浓度也会促进气体扩散层内的盐沉淀，导致系统耐久性较差。在这里，我们通过用固态质子导体代替液体阴极电解液来调节H传输，从而解决了这个难题。据推测，这可以在阴极形成局部碱性环境，即使没有碱金属阳离子也能实现选择性COR。我们表明，这种策略在广泛的催化剂体系中都是有效的。例如，使用复合纳米多孔Au和单原子Ni催化剂，以0.25 M HSO作为阳极电解液，在300 mA/cm下我们实现了87%的CO法拉第效率（FE）。还成功证明了在110 h内的稳定运行以及82.8%的高单程碳效率。重要的是，我们发现这种固态系统在转化稀释原料（5% CO）方面也特别有效，CO FE为47.7%，比传统系统高16.4倍。我们的结果为开发高效的酸性COR电解槽引入了一种简单而有效的设计方法。
