Proton-Independent CO₂-to-CO Photoreduction Coupled with NO Oxidation in a Controlled Coexisting System

¹ School of Resources and Environment, University of Electronic Science and Technology of China, Chengdu 611731, China.
² Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 611731, China.

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

CO₂ and NO commonly coexist in flue gas, yet they are typically treated as independent targets in photocatalysis. Here we demonstrate that introducing NO can strongly promote photocatalytic CO₂-to- CO conversion over TiO₂ P25 in a batch gas-phase system. And larger NO inputs yield higher CO output per dosing event. Product analysis shows that NO is predominantly oxidized to NO₂ and surface nitrate, as evidenced by flue-gas analysis and ion chromatography of catalyst eluates, whereas CO is essentially the only detectable CO₂ reduction product. In situ DRIFTS further identifies the growth of nitrate/nitrite-like bands (1650–1250 cm⁻¹) during illumination under CO₂ + NO. Importantly, the NO-triggered CO formation persists under anhydrous conditions, indicating that CO₂-to-CO conversion can proceed without an external proton source and is inconsistent with a purely PCET-driven pathway. These results suggest an OCET-like coupling scenario in which NO oxidation provides an efficient oxidative channel, suppresses charge recombination, and enhances electron utilization for selective CO production.