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Keywords:

  • CO oxidation;
  • copper;
  • DFT;
  • selectivity;
  • titania;
  • water–gas shift

Abstract

As an early attempt to tune the selectivity of Cu catalysts through oxide deposition, we performed DFT calculations to study the water-gas shift (WGS) and CO oxidation reactions at the interface of Cu(1 1 1) modified by TiO2 clusters [TiO2/Cu(1 1 1)]. Pure Cu catalyzes both reactions, though the overall conversion is hindered by either H2O dissociation or O2 dissociation. Our results show that after depositing TiO2, TiO2/Cu(1 1 1) promotes the CO oxidation reaction and suppresses the WGS reaction. The active Ti3f[BOND]Cu site at the TiO2/Cu(1 1 1) interface plays an essential role in tuning the selectivity. During the CO oxidation reaction, the Ti3f[BOND]Cu site enables the facile O2 dissociation at the interface, which leads to the oxidation of the surface layer on Cu(1 1 1) and the formation of Cu2O. According to our calculations, the produced TiO2/Cu2O(1 1 1) interface is active toward CO oxidation, which not only binds O2 and CO well but also enables a facile O[BOND]O bond cleavage via the OO[BOND]CO intermediate. During the WGS reaction, the Ti3f[BOND]Cu site is poisoned by CO and the rate-limiting H2O dissociation and therefore the overall WGS is hindered. The results suggest that high selectivity, one of the focuses for next generation catalysts, can be achieved by modifying the chemical properties of the interface.