Research progress on electrocatalyst design for low-concentration CO₂ conversion

The achievement of carbon peak and carbon neutrality goals urgently demands efficient carbon emission reduction and resource utilization technologies. Electrocatalytic CO₂ reduction stands out as a key pathway due to numerous advantages, including mild reaction conditions, tunable parameters, and compatibility with renewable energy sources. However, current research predominantly focuses on converting high-purity CO₂, while the direct conversion of low-concentration CO₂ from major global emission sources （e.g., flue gas from coal-fired power plants containing only about 15% CO₂） and the atmospheric environment （about 0.04% CO₂） faces severe challenges, such as severe mass transfer limitations stemming from low reactant concentration, sluggish reaction kinetics, and low product selectivity. Addressing such bottlenecks necessitates breakthroughs in electrocatalyst design. Building upon an introduction to the mechanism of eCO₂RR, this paper specifically analyzes the limiting factors for electrocatalytic low-concentration CO₂ reduction. Subsequently, we systematically review design strategies for electrocatalysts targeting low-concentration CO₂ conversion, revealing the regulatory logic from microstructure to macroscopic performance. This review aims to provide a theoretical framework for constructing efficient catalytic systems. Size engineering enables the formation of nanomaterials or atomically dispersed active sites, significantly increasing the specific surface area of the catalyst and providing a higher density of active sites, while also influencing intrinsic activity. Morphology control allows precise tuning of catalyst microstructure, enhancing activity through various pathways such as increasing specific surface area and exposing highly active crystal facets. Defect engineering effectively modifies surface composition, charge distribution, electronic structure, and active sites, thereby influencing reaction pathways, activity, and selectivity. Molecular modification, which introduces molecules onto or within the catalyst, can promote CO₂ adsorption, stabilize intermediates, accelerate electron transfer, and suppress particle aggregation. Biomimetic Design simulates enzymatic microenvironments to rapidly interconvert \mathrmHCO_3^- and CO₂, overcoming mass transfer limitations under low CO₂ concentrations. Furthermore, the synergistic integration of multiple design strategies can overcome limitations of individual approaches and maximize their advantages, achieving superior catalytic performance. Alongside the systematic review of catalyst design strategies, relevant characterization techniques and theoretical calculation methods commonly employed are introduced, providing crucial experimental validation and mechanistic insights. Nevertheless, current research still faces challenges such as poor stability of catalysts in complex flue gas environments, low selectivity for C₂₊ products, and industrial-scale implementation. Future research focusing on the eCO₂RR mechanism and catalyst performance under simulated flue gas or atmospheric conditions is expected to promote the practical application of low-concentration CO₂ electrocatalytic technology, providing key scientific and technological support for achieving carbon peak and carbon neutrality goals.