Au Clusters Supported on Defect-Rich Ni-Ti Oxides Derived from Ultrafine Layered Double Hydroxides (LDHs) for CO Oxidation at Ambient Temperature

Ultrafine layered double hydroxides (LDHs) have abundant hydroxy groups at their edge sites, serving as anchor sites for metal NPs. Furthermore, transformation of ultrafine LDHs into mixed metal oxides (MMOs) generates abundant oxygen vacancies, which are advantageous for O-2 activation during Au-catalyzed CO oxidation. We used ultrafine Ni-Ti LDHs with low crystallinity or Ni-Ti MMOs supported on SiO2 onto which Au NPs were deposited by deposition-precipitation (DP) and DP-urea (DPU). The catalytic activity of the Au catalysts was significantly affected by the preparation method, with the highest activity obtained by depositing Au onto LDH/SiO2 by DPU, followed by transformation of LDH to MMO (Au/Ni-Ti MMO/SiO2 (LDH-DPU)). The presence of Au on LDHs affected the transformation of LDHs into MMOs, resulting in LDH-DPU having the greatest number of oxygen vacancies in the TiO2 domain in MMOs. Consequently, the adsorbed or the lattice oxygen on the surface of LDH-DPU can be easily utilized for CO oxidation at low temperatures. Moreover, the catalytic activity of LDH-DPU increased with water vapor concentration up to 100% relative humidity at room temperature, suggesting the potential of Au/Ni-Ti MMO/SiO2 as an air purification catalyst.