Acidic-alkaline tandem system for durable CO<sub>2</sub>-CO-C<sub>2</sub>.

Ma, Xianhui; Zhang, Juan; He, Dayin; Jiang, Wei; Sun, Yuanhua; Cui, Jiayi; Chen, Cai; Lin, Yue et al. · Sci Adv · 2026

basic_science · Level V

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Abstract

Tandem carbon dioxide reduction reaction (CO<sub>2</sub>RR) to multicarbon products (CO<sub>2</sub>-CO-C<sub>2+</sub>) such as ethylene represents a pivotal strategy for carbon valorization. However, conventional alkaline or neutral tandem systems limit the carbon dioxide utilization and stability due to severe (bi)carbonate formation. Here, we design a durable acidic-alkaline tandem system to efficiently synthesize C<sub>2+</sub> products, especially ethylene. In the acidic CO<sub>2</sub>RR step, a catalyst with precisely controlled metal site distance was used to regulate *COOH adsorption. Typically, a 99.7 ± 0.4% carbon monoxide Faradaic efficiency (FE) at 1.4 amperes per square centimeter can be achieved using a catalyst with 0.5-nanometer nickel sites, surpassing the previously reported metal catalysts. When this catalyst was integrated into the acidic-alkaline tandem system and coupled with the alkaline carbon monoxide electroreduction, the ethylene and C<sub>2+</sub> FE reached 75.3 ± 1.2 and 92.5 ± 1.3% at 10 amperes, respectively, and remained stable for 400 hours. Our work provides solutions for the durable conversion of carbon dioxide to C<sub>2+</sub> products from catalyst and electrolyzer design.