Oxygen vacancy promoted H2O activation over K⁺-doped -MnO₂ for low-temperature HCHO oxidation

H2O activation plays a crucial role in the oxidation process of HCHO, which can create active hydroxyl to attack HCHO molecules and enhance the catalytic activity. Therefore, the construction of highly active sites for H2O activation to accelerate the reaction rate is required. Herein, we constructed and regulated the surface oxygen vacancies over epsilon-MnO2 with the aid of K doping to activate H2O through a simple hydrothermal method. The role of oxygen vacancy produced by K+ doping for H2O activation in HCHO removal was investigated by various technologies, including XPS, TPD, TPSR, and in-situ DRIFTS. It was found that the addition of K+ not only increased the adsorption sites for negatively charged oxygen atoms of HCHO but also provided oxygen vacancies to induce more active hydroxyl species from water activation. The optimal K+-doped epsilon-MnO2 significantly removed 90% of HCHO at 74 degrees C (GHSV = 120 L/g.h, HCHO = 70 ppm). After the stability test at 65 and 80 degrees C for 100 h respectively, the conversion did not show a downward trend. This work innovatively developed a K-doped epsilon-MnO2 catalyst with surface oxygen vacancy to activate H2O and revealed the role of K+ and oxygen vacancy for efficient HCHO oxidation.