Gas-Phase Photoelectrocatalysis for Breaking Down Nitric Oxide

Photoelectrocatalysis (PEC) produces high-efficiency electron-hole separation by applying a bias voltage between semiconductor-based electrodes to achieve high photocatalytic reaction rates. However, using PEC to treat polluted gas in a gas-phase reaction is difficult because of the lack of a conductive medium. Herein, we report an efficient PEC system to oxidize NO gas by using parallel photoactive composites (TiO₂ nanoribbons-carbon nanotubes) coated on stainless-steel mesh as photoanodes in a gas-phase chamber and Pt foil as the working electrode in a liquid-phase auxiliary cell. Carbon nanotubes (CNTs) were utilized as conductive scaffolds to enhance the interaction between TiO₂ and stainless-steel skeletons for accelerated photogenerated electron transfer. Such a PEC system exhibited super-high performance for the treatment of indoor NO gas (550 ppb) with high selectivity for nitrate under UV-light irradiation owing to the conductive, intertwined network structure of the photoanode, fast photocarrier separation, and longer photogenerated hole lifetime. The photogenerated holes were proven to be the most important active sites for directly driving PEC oxidation of indoor NO gas, even in the absence of water vapor. This work created an efficient PEC air-purification filter for treating indoor polluted air under ambient conditions.