Efficient low-temperature NO reduction via constructing Cu⁺ -O-Co³⁺ sites to enhance lattice oxygen release and CO...

Transition metal oxide catalysts exhibit limited activity and N₂ selectivity for the reduction of NO by CO at low temperatures (<200 °C), due to insufficient oxygen mobility and competitive NO/CO adsorption. Herein, a series of copper-cobalt composite oxides (Cu_xCo_3-x,x = 0, 0.25, 0.5, 1, 1.5, 2, and 3) catalysts with varying molar ratios were systematically synthesized for constructing the Cu⁺-O-Co³⁺ sites to promote lattice oxygen release and CO adsorption. Specifically, the Cu_1.5Co_1.5 catalyst, which is abundant in Cu⁺-O-Co³⁺ sites, achieves a remarkable balance between activity and selectivity, with over 95 % NO conversion at 125 °C, over 90 % N₂ selectivity at 200 °C, and over 95 % CO conversion at 200 °C. X-ray absorption fine structure (XAFS) spectroscopy and complementary characterization results indicate that the expansion of the Co-O bond and contraction of the Cu-O bond within the Cu⁺-O-Co³⁺ sites promote the release of lattice oxygen and enhance CO adsorption. This structure promotes the formation and conversion of key intermediates, including *ONNO dimers and nitrites, steering the reaction pathway toward selective N₂ formation. This work highlights the importance of tailoring the local atomic structure over merely maximizing oxygen vacancies, providing a paradigm for designing efficient CO-SCR catalysts.