Highly active nanostick-assembled TiO2@MnOx hollow-sphere structure for photothermocatalysis of ethyl acetate and NO with free-ammonia at low temperature: Resistence, key reaction steps and mechanisms

Abstract

In this work, a series of self-assembled nanosticks into hollow-sphere structure of TiO2-MnOx (H1 sample), TiO2@MnOx (H2 sample) and MnOx@TiO2 (H3 sample) catalysts were successfully established. These samples were used to investigate the resistance to SO2 and H2O, key reaction steps, and the possible catalytic mechanisms for the photothermocatalytic removal of ethyl acetate and NO with free-ammonia at low temperature. Among all the samples, sample H2 exhibited the best catalytic activity, which exhibited 70% NO conversion and 56% ethyl acetate degradation at 240 ℃ under SO2 and H2O. The catalyst was resistant to SO2 and H2O and potentially benefited from the hollow structure’s protection of active components. Moreover, the sample H2 loaded first with manganese and then with titanium, was favorable for the oxidation of ethyl acetate into small-molecule intermediates, thereby improving NO conversion. This indicated that the partial oxidation of ethyl acetate as the reductant for NO conversion was a key step of the simultaneous degradation of VOCs and NO. In addition, organic by-products of ethyl acetate and NO degradation, such as ethane and ethanol, were found. Finally, the theoretical results of Density Functional Theory (DFT) calculations revealed that ethyl acetate was more easily converted into CH3CH2· and CH3COO· groups in our system.