Analysis of the thermochemistry of NO_x decomposition over CuZSM-5 based on quantum chemical and statistical mechanical calculations

CuZSM-5 is the most active catalyst known for the direct decomposition of NO_x. We have performed first-principles quantum mechanical calculations to evaluate the electronic and structural properties of species adsorbed to Cu sites that might be involved in NO_x decomposition. Using statistical mechanics, we have calculated ΔU○, ΔH○, and ΔG○ of possible elementary reactions in order to evaluate the stability of adsorbates on Cu sites and the ease of their interconversion. On the basis of these calculations, we propose a reaction pathway for NO_x decomposition. This scheme involves only single, isolated copper sites, is internally consistent, and is consistent with experimental observations.