Catalytic ozonation for low-temperature NOX (x = 1, 2) removal with OH radicals over Cu doped Ce0.90Co0.10O2 − δ catalysts and mechanism analysis

•Nanocrystalline Ce0.90 Co0.10 O2-δ and Ce0.90-x Cux Co0.10 O2-δ (x = 0.03, 0.07, 0.10) catalysts were synthesized.•A novel catalyst-duct separation system for NOX removal by catalytic ozonation was developed.•The hydroxyl radical could be “transferred” from catalyst surface to the duct through its reproduction reaction.•Ce0.83 Cu0.07 Co0.10 O2-δ significantly enhanced catalytic performance for NOX removal.•The activation bridging O played an important role in promoting the generation of OH radicals.

A series of Ce0.90Co0.10O2 − δ and Ce0.90 − xCuxCo0.10O2 − δ (x = 0.03, 0.07 and 0.10) catalysts synthesized by an alkaline hydrothermal method were utilized as ozonation catalysts for the NOX (x = 1, 2) removal at low temperatures. A novel catalyst-duct separation apparatus for denitrification by catalytic ozonation was developed by our group. Ce0.83Cu0.07Co0.10O2 − δ exhibits the highest catalytic activity (91.5% removal at 120 °C), whereas Ce0.80Cu0.10Co0.10O2 − δ presents the lowest (74.1% removal at 120 °C). Only NO3− is detected in the tail solutions. The catalytic performance presents a positive relationship with the corresponding OH concentration. OH radical can be “transferred” from catalyst surface to the duct, prolonging activation time through its own reproduction reaction. The surface -OH activation, not the surface -OH density determines the OH concentration in the present method. Ce0.83Cu0.07Co0.10O2 − δ contains a large number of high-activation bridging -OH, whereas the bridging -OH is absent in Ce0.80Cu0.10Co0.10O2 − δ. Therefore, Ce0.83Cu0.07Co0.10O2 − δ shows much higher activation for promoting the formation of OH than Ce0.80Cu0.10Co0.10O2 − δ.

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