Catalytic oxidation of formaldehyde on ultrathin Co3O4 nanosheets at room temperature: Effect of enhanced active sites exposure on reaction path

This research precisely controlled the thickness of Co 3 O 4 nanosheets to investigate the effect of active sites exposure on the reaction path of HCHO catalytic oxidation. X-ray absorption fine structure demonstrates that ultrathin Co 3 O 4 nanosheets (Co 3 O 4 -2) with atomic layer thickness (~2 nm) exhibit stronger lattice disorder than Co 3 O 4 nanosheets with a thickness of 20 nm (Co 3 O 4 -20). Aberration-corrected scanning transmission electron microscopy confirms that two-dimensional structure and disordered structure of Co 3 O 4 -2 enhances the surface exposure of active sites (Co 3+ and oxygen vacancies). Therefore, Co 3 O 4 -2 can produce more reactive oxygen species, avoiding the side reaction path dominated by undesired intermediates over Co 3 O 4 -20, where active sites are blocked and HCHO oxidation is inhibited. Consequently, the HCHO removal efficiency (＞90%) and CO 2 conversion efficiency (＞90%) of Co 3 O 4 -2 are substantially higher than thicker Co 3 O 4 nanosheets. This research provides an effective strategy to construct active sites and deep insights into the reaction path. • Ultra-thin Co 3 O 4 nanosheets achieved catalytic oxidation of HCHO at room temperature. • The thickness of Co 3 O 4 nanosheets is precisely controlled. • Enhanced active sites exposure was studied from the atomic scale. • Abundant active sites of ultra-thin Co 3 O 4 nanosheets eliminate side reaction paths.