Electrocatalytic and Photoelectrocatalytic Degradation of Gaseous Pollutants: Toward Spatially Separated Redox Reactions

Abstract Catalytic degradation of gaseous pollutants based on nanomaterials has long relied on oxidation-driven processes. However, these approaches share a fundamental structural limitation: oxidation and reduction sites are spatially co-located on the catalyst surface, resulting in rapid charge recombination, poor reaction selectivity, and limited tunability of the reaction driving force. Spatial separation of redox sites, achieved through electrocatalytic (EC) and photoelectrocatalytic (PEC) systems, offers a conceptually distinct solution. By decoupling anodic and cathodic reactions through an external bias, EC and PEC systems enable direct control over charge carrier lifetime, reactive oxygen species, and reaction selectivity that is structurally unachievable with conventional catalysts. This review systematically discusses the fundamentals of the gas-solid electrochemical interface, governed by distinct constraints, including the triple-phase boundary, trace-level mass transfer, and the dual role of water, followed by the reaction mechanisms and interfacial design principles of EC and PEC systems. Reactor configurations and state-of-the-art characterization techniques are also introduced. Framing these advances as a shift from material-centered catalysis toward reaction-centered design, the potential applicability of spatially separated redox reactions to emerging refractory pollutants, including halogenated VOCs and PFAS, is also discussed, establishing this approach as a selective and controllable framework for air purification.