Tailored ozone activation on geometrical-site-dependent cobalt with selective coordination

Area of Science:

• Materials Science
• Catalysis
• Surface Chemistry

Background:

• Cobalt-containing spinel oxides offer tunable catalytic properties by modifying geometric sites.
• The precise role of different cobalt species (Co2+Td and Co3+Oh) in catalytic activity is debated.

Purpose of the Study:

• To investigate the distinct catalytic roles of tetrahedrally coordinated Co2+ (Co2+Td) and octahedrally coordinated Co3+ (Co3+Oh) in ozone activation.
• To elucidate the mechanism of geometrical-site-dependent ozone decomposition on spinel oxide surfaces.

Main Methods:

• Engineered cobalt spinel oxide catalysts with controlled [111] crystal facet exposure by substituting inactive cations.
• Investigated ozone activation mechanisms on isolated Co2+Td and Co3+Oh sites.

Main Results:

• Highly spin-polarized Co2+Td sites demonstrated superior activity for ozone activation compared to Co3+Oh sites.
• Co2+Td sites facilitated strong orbital interactions and electron transfer with ozone, selectively generating hydroxyl radicals (•OH) and suppressing singlet oxygen (1O2).
• Achieved a 17.6-fold increase in turnover frequency (TOF) attributed to the Co2+Td sites.

Conclusions:

• Spin-polarized electronic states of Co2+Td sites are crucial for regulating reaction thermodynamics in transition metal oxide catalysis.
• Geometric site engineering of spinel oxides provides a pathway for designing highly active and selective catalysts for ozone decomposition.