Hydrothermally synthesized CuxO as a catalyst for CO oxidation

Abstract

Hydrothermally synthesized Cu_xO exhibited improved performance for CO oxidation compared to the hydrothermally synthesized Cu₂O, as well as commercial CuO nanoparticles. Hydrothermally synthesized Cu_xO predominantly consists of CuO, but it also contains a small contribution from Cu₂O, as well as Cu₂(OH)₃(NO₃) (before annealing). After annealing, only CuO and Cu₂O phases are present, and the T₅₀ value is significantly improved from 179 °C to 149 °C, and the T₅₀ value of annealed hydrothermal Cu_xO remains practically unchanged for 3 catalytic cycles. The improved performance of hydrothermal Cu_xO can be attributed to its composition and surface properties. The ratio of lattice oxygen to surface oxygen (oxygen in surface adsorbates, surface states, and defects) increases after the first CO oxidation reaction for all samples except commercial CuO nanoparticles, which exhibit steady decrease with increased cycling. In addition, pure Cu₂O irreversibly changes to CuO after CO oxidation reaction, but its catalytic performance after the first cycle is significantly improved compared to commercial CuO nanoparticles.