Electronic and Atomistic Roles of Cordierite Substrate in Sintering of Washcoated Catalysts for Automotive Exhaust Gas Emissions Control: Multi-scale Computational Chemistry Approach based on Ultra-Accelerated Quantum Chemical Molecular Dynamics Method

Multi-scale computational chemistry methods based on the ultra-accelerated quantum chemical molecular dynamics (UA-QCMD) are applied to investigate electronic and atomistic roles of cordierite substrate in sintering of washcoated automotive catalysts. It is demonstrated that the UA-QCMD method is effective in performing quantum chemical molecular dynamics calculations of crystals of cordierite, Al₂O₃ and CeZrO₄ (hereafter denoted as CZ). It is around 10,000,000 times faster than a conventional first-principles molecular dynamics method based on density-functional theory (DFT). Also, the accuracy of the UA-QCMD method is demonstrated to be as high as that of DFT. On the basis of these confirmations and comparison, we performed extensive quantum chemical molecular dynamics calculations of surfaces of cordierite, Al₂O₃ and CZ, and interfaces of Al₂O₃ and CZ with cordierite at various temperatures. These calculations coupled with mesoscopic sintering simulations have demonstrated that the cordierite surface forms strong bonds with Al₂O₃ and CZ, which was seen to improve significantly the sintering property of washcoated catalysts under various conditions.