Boosting catalytic activity of Cu-Ce solid solution catalysts by flame spray pyrolysis with high Cu+ concentration and oxygen vacancies

[Display omitted] •The solubility of Cu is increased due to the extremely high temperature in the flame.•A controllable synthesis of a high-Cu content (30%) solid solution was achieved.•The highly active Cu+ enrichment on surface increases the catalytic reactive sites.•The Cu+ sites and oxygen vacancies promote CO catalytic oxidation performance.•Cu-30 has a reaction rate of 0.48 μmolCO g−1 s−1 at 60 °C, complete at 120 °C. Cu-Ce solid solution catalysts are remarkable in catalytic oxidation. However, the traditional synthesis methods struggle to prevent severe phase separation at high Cu concentration. In this study, a stable Cu-Ce solid solution with a Cu content>30% was synthesized by flame spray pyrolysis (FSP). Flame synthesis process with a high reaction temperature of 2000 K and rapid cooling characteristics of over 100 K cm−1 resulted in the enrichment of Cu elements on the catalyst's surface as Cu+. The high Cu content fostered abundant surface oxygen vacancies on the catalyst. The catalyst surface has more CO activation sites due to the high Cu+ concentration, and the abundant oxygen vacancies bring greater oxygen activation ability to the catalyst. It was found that Cu-30 had a reaction rate of 0.48 μmolCO g−1 s−1 at 60 °C, dozens of times higher than other catalysts, and achieved complete conversion of CO at 120 °C. The mechanism suggests that the active site of CO is the surface Cu+, and the oxygen vacancies provide active oxygen species, which facilitate the CO catalytic reaction's rapid progress.