Dynamic valence engineering of CuOx catalysts for selective and stable CO2 electroreduction to ethylene and ethanol

Cu-based oxide (CuO_x) catalysts have emerged as promising candidates for electrochemical CO₂ reduction to C₂ products such as ethylene (C₂H₄) and ethanol (C₂H₅OH). However, the simultaneous realization of high selectivity and long-term stability remains a critical challenge. This review systematically summarizes the fundamental mechanisms governing C–C coupling on CuO_x catalysts, emphasizing the role of dynamic valence states, facet effects, coordination environments and local reaction microenvironments. The divergent formation pathways of C₂H₄ and C₂H₅OH are discussed in detail, focusing on intermediate evolution, competitive adsorption (*CO, *H, *OH) and electronic structure modulation. Key structure-activity relationships are revealed, offering insights into how oxidation state engineering can steer product selectivity. In parallel, degradation pathways such as Cu⁺ reduction, particle aggregation, and morphological collapse are analyzed, and advanced stability-by-design strategies including pulse electrolysis, heterostructure construction, doping, and surface coating are critically reviewed. Looking ahead, operando characterization, valence-interface precision engineering, and scalable catalyst architectures are expected to play critical roles in enabling the industrial implementation of CO₂-to-C₂ conversion. By bridging mechanistic understanding with design strategies, this work provides a comprehensive framework for the rational development of efficient and durable CuO_x catalysts.