Tailoring oxygen vacancies and active surface oxygen species in CrO_x hierarchical strawberry-type three-dimensional (3D) micro-spindle catalysts for total catalytic oxidation of VOCs

Developing efficient and stable non-noble metal catalysts for the catalytic oxidation of volatile organic compounds (VOCs) has always been key for controlling air pollution. Chromium oxide nanoparticle catalysts act as a potential material for this purpose, and their morphology has a significant impact on the catalyst performance. Herein, two types of chromium oxides with different morphologies were prepared using two different precursors in a hydrothermal route: one that was synthesized using chromic acid and exhibited a strawberry micro-spindle type morphology consisting of innumerable nanoparticles in the range of similar to 20-35 nm, and the other one that was synthesized using a nitrate precursor and consisted of thoroughly dispersed nanoparticles in the range of 30-40 nm. Both of them were successfully applied for the total oxidation of toluene. The former exhibited higher efficiency; for long-term stability of the catalyst, K+ ions were added during its synthesis. Importantly, the former catalyst was superior to the latter one because of the ease of activation and migration of lattice oxygen, which was comprehensively understood using H-2-TPR, O-2-TPD and XPS analyses.