In situ visualizing reveals potential drive of lattice expansion on defective support toward efficient removal of nitrogen oxides.

As a sustainable and promising approach of removing of nitrogen oxides (NO x ), catalytic reduction of NO x with H 2 is highly desirable with a precise understanding to the structure-activity relationship of supported catalysts. In particular, the dynamic evolution of support at microscopic scale may play a critical role in heterogeneous catalysis, however, identifying the in situ structural change of support under working condition with atomic precision and revealing its role in catalysis is still a grand challenge. Herein, we visually capture the surface lattice expansion of WO 3-x support in Pt-WO 3-x catalyst induced by NO in the exemplified reduction of NO with H 2 using in situ transmission electron microscopy and first reveal its important role in enhancing catalysis. We find that NO can adsorb on the oxygen vacancy sites of WO 3-x and favorably induce the reversible stretching of W-O-W bonds during the reaction, which can reduce the adsorption energy of NO on Pt 4 centers and the energy barrier of the rate-determining step. The comprehensive studies reveal that lattice expansion of WO 3-x support can tune the catalytic performance of Pt-WO 3-x catalyst, leading to 20% catalytic activity enhancement for the exemplified reduction of NO with H 2 . This work reveals that the lattice expansion of defective support can tune and optimize the catalytic performance at the atomic scale.