Abstract: The Co₃O₄ nanoparticles, dominated by a catalytically active (110) lattice plane, were synthesized as a low-temperature NO_x adsorbent to control the cold start emissions from vehicles. These nanoparticles boast a substantial quantity of active chemisorbed oxygen and lattice oxygen, which exhibited a NO_x uptake capacity commensurate with Pd/SSZ-13 at 100°C. The primary NO_x release temperature falls within a temperature range of 200–350°C, making it perfectly suitable for diesel engines. The characterization results demonstrate that chemisorbed oxygen facilitate nitro/nitrites intermediates formation, contributing to the NO_x storage at 100°C, while the nitrites begin to decompose within the 150–200°C range. Fortunately, lattice oxygen likely becomes involved in the activation of nitrites into more stable nitrate within this particular temperature range. The concurrent processes of nitrites decomposition and its conversion to nitrates results in a minimal NO_x release between the temperatures of 150–200°C. The nitrate formed via lattice oxygen mainly induces the NO_x to be released as NO₂ within a temperature range of 200–350°C, which is advantageous in enhancing the NO_x activity of downstream NH₃-SCR catalysts, by boosting the fast SCR reaction pathway. Thanks to its low cost, considerable NO_x absorption capacity, and optimal release temperature, Co₃O₄ demonstrates potential as an effective material for passive NO_x adsorber applications.

Key words: Emission control, Cold-start, Low-temperature adsorption, Co₃O₄, Nitrate formation

摘要： The Co₃O₄ nanoparticles, dominated by a catalytically active (110) lattice plane, were synthesized as a low-temperature NO_x adsorbent to control the cold start emissions from vehicles. These nanoparticles boast a substantial quantity of active chemisorbed oxygen and lattice oxygen, which exhibited a NO_x uptake capacity commensurate with Pd/SSZ-13 at 100°C. The primary NO_x release temperature falls within a temperature range of 200–350°C, making it perfectly suitable for diesel engines. The characterization results demonstrate that chemisorbed oxygen facilitate nitro/nitrites intermediates formation, contributing to the NO_x storage at 100°C, while the nitrites begin to decompose within the 150–200°C range. Fortunately, lattice oxygen likely becomes involved in the activation of nitrites into more stable nitrate within this particular temperature range. The concurrent processes of nitrites decomposition and its conversion to nitrates results in a minimal NO_x release between the temperatures of 150–200°C. The nitrate formed via lattice oxygen mainly induces the NO_x to be released as NO₂ within a temperature range of 200–350°C, which is advantageous in enhancing the NO_x activity of downstream NH₃-SCR catalysts, by boosting the fast SCR reaction pathway. Thanks to its low cost, considerable NO_x absorption capacity, and optimal release temperature, Co₃O₄ demonstrates potential as an effective material for passive NO_x adsorber applications.

关键词: Emission control, Cold-start, Low-temperature adsorption, Co₃O₄, Nitrate formation