Mechanistic study of low-temperature CO oxidation over CuO/Cu2O interfaces with oxygen vacancy modification

Abstract

Copper oxides have attracted great attention in the oxidation of CO due to their high activity at low temperatures. In this work, novel CuO/Cu2O heterojunction catalysts for low-temperature CO oxidation was prepared via hydrothermal in-situ oxidizing in H2O2. Based on studies of surface composition and the corresponding catalytic activities, the CuO/Cu2O catalysts contain rich oxygen vacancies (OVs), which improve the activation and migration ability of O2. The coupling effect between OVs and heterojunction reduces the activation energy of CO oxidation, leading the temperature of CO completed oxidation temperature from 250 °C to 140 °C. In addition, the in-situ Fourier transform infrared spectroscopy (in-situ FTIR) and Density functional theory (DFT) studies confirm two reaction paths under Langmuir-Hinshelwood (LH) mechanism: a low barrier path takes place at low temperature, and another new reaction path with a barrier of 1.8 eV can take place at a high temperature. The new reaction site formed at the CuO/Cu2O interface resulted in different activation modes of CO and O2. The modification of OVs significantly reduces the reaction temperature required. This work provides a method to improve the performance of co-catalytic oxidation via the coupling effect of OVs and heterojunctions.