Charge polarization as an electronic descriptor for C–C coupling in photocatalytic CO₂ reduction

The selective photocatalytic conversion of CO₂ into high-value multicarbon (C₂₊) products remains fundamentally constrained by the intrinsic mismatch between ultrafast photogenerated charge carriers’ recombination and the kinetically demanding C–C coupling process. While extensive efforts have focused on material development, a unifying electronic principle governing C₂₊ formation is still lacking. Here, we propose charge polarization as a quantitative electronic descriptor that dictates both the energetic asymmetry of adsorbed intermediates and the stabilization of C–C coupling transition states. By deliberately constructing asymmetric charge distributions at catalytic interfaces, polarization simultaneously establishes built-in electric fields that prolong carrier lifetimes and generates differentiated adsorption sites capable of decoupling scaling relationships between key C₁ intermediates. This dual functionality, conceptualized as a charge pump-molecular recognition synergy, bridges excited-state photophysics with ground-state surface chemistry. We systematically analyze how atomic coordination, defect structures, interfacial heterojunctions, metal–semiconductor contacts, and intrinsically polar materials modulate polarization strength and spatial configuration to regulate C–C bond formation pathways. Furthermore, we discuss how polarization-driven electronic asymmetry enables the selective stabilization of high-energy intermediates and suppresses competing hydrogen evolution. By reframing charge polarization as a fundamental electronic design descriptor rather than a structural feature, this review provides mechanistic insights and actionable principles for the rational design of next-generation photocatalysts for CO₂-to-C₂₊ conversion.