State of the Art Review on Photocatalytic Fog Seal for Asphalt Pavement: Material Composition, Performance Characterization, Catalytic Mechanism, and Efficacy Enhancement

Photocatalytic fog seal technology for asphalt pavement suffers from unclear photocatalyst selection criteria, incomplete testing and evaluation systems, and poorly understood efficacy enhancement mechanisms. This review systematically examines the material composition of photocatalytic fog seals, focusing on photocatalyst types and photoelectric properties. Oxide, nitride, and sulfide photocatalysts are compared in terms of band gap, absorption edge wavelength, photoresponse region, specific surface area, and solar light utilization. Characterization indicators are classified into efficiency, kinetic, and physicochemical categories: efficiency indicators reflect photocatalytic effectiveness, kinetic indicators describe reaction rates, and physicochemical indicators explain intrinsic performance differences. Current testing devices for efficiency indicators are summarized, existing challenges are identified, and essential design features are proposed. The photocatalytic mechanism, including photoexcitation, charge carrier separation, and interfacial catalysis, is elucidated. Performance enhancement strategies—element doping, heterostructure construction, morphology and structure regulation, support loading, and piezo-photocatalytic synergy—are reviewed. Under combined light and mechanical loading, the NO degradation efficiency was 139% and 48% higher than that under pure piezoelectric and pure photocatalytic conditions, respectively. Persistent issues include missing photocatalyst selection standards, neglected binder embedding effects, inconsistent testing methods, poor cross-comparability, laboratory-field discrepancies, and insufficient long-term validation. Accordingly, future research directions and priorities for photocatalytic fog seal technology are identified.