Electrochemical low-concentration CO₂ capture and conversion: from catalyst design to electrolyzer engineering

Electrochemical CO₂ reduction (CO₂RR) offers a promising route to convert CO₂ into value-added fuels and chemicals using renewable electricity. However, most studies rely on high-purity CO₂ feeds, whereas practical carbon sources such as flue gas and air contain dilute CO₂ together with diverse impurities. These conditions lead to sluggish CO₂ mass transport, enhanced hydrogen evolution reaction (HER), and impurity-induced catalyst deactivation, thereby limiting CO₂RR activity, selectivity, and durability. This review systematically summarizes recent advances in low-concentration CO₂ electrochemical capture and conversion, focusing on two main technical routes. The first is capture–conversion coupling, in which CO₂ is captured and subsequently converted in situ into value-added products within single- or dual-cell systems, thereby avoiding energy-intensive capture-medium regeneration, CO₂ compression, and transportation. The second is direct electrolysis of dilute CO₂ streams, which bypasses separate capture units through catalyst design. In both routes, catalyst design has evolved from solely optimizing intrinsic CO₂RR activity toward multifunctional regulation, including captured-CO₂ activation, local CO₂ enrichment, and impurity tolerance. Beyond catalyst development, electrolyzer design, such as gas diffusion layer design, flow-field configuration, and operating condition optimization, is also discussed as a key factor for improving mass transport and stability. Finally, remaining challenges and future opportunities are outlined for selective, durable, and scalable low-concentration CO₂ electrolysis.