In this study, α-, β-, and δ-MnO₂ were prepared by a uniform hydrothermal method and then coupled with vacuum ultraviolet (VUV) for the degradation of gaseous unsymmetrical dimethylhydrazine (UDMH). The performance in the remove of UDMH, by-products distribution and mechanistic insights were systematically investigated. The catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption/desorption, Field Emission Scanning Electron Microscopy (FE-SEM), Raman, thermal gravimetric (TG), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) to investigate the factors affecting the catalytic activity. The results showed that O₂ and H₂O were essential for the remove of UDMH . The integrated process considerably improved the remove and mineralization of UDMH by ozone catalytic oxidation . There were more reactive oxygen species generated in the integrated process. The catalytic activity of the prepared catalysts following the order: δ-MnO₂ >α-MnO₂ >β-MnO₂. δ-MnO₂ displayed the highest remove rate of 100% and CO₂ concentration of 42 ppmv. The good performance of δ-MnO₂ was attributed to high specific surface area and surface oxygen vacancies.

XRD data
The raw data of XRD patterns belong to MnO₂ (Fig.2).

N₂ adsorption-desorption isotherms
N₂ adsorption−desorption isotherms of α-, β- and δ-MnO₂ (Fig.3).

Raman Spectroscopy
Raman spectra of α-, β- and δ-MnO₂ (Fig.5).

FTIR spectroscopy
FTIR spectra of α-, β-, δ-MnO₂ and α-MnO₂ after the reaction (Fig.6).

TG
TG analyses curves of α-, β-, and δ-MnO₂ (Fig.7).

XPS
Mn 2p_2/3, Mn 3s and O 1s XPS spectra of α-, β-, and δ-MnO₂ (Fig.8).

Degradation of UDMH
The data and calculations of the degradation of UDMH and the concentration of CO₂ in the continuous flow fixed-bed steel reactor.

GC-MS spectra
GC-MS spectra of organic products from (a) VUV photolysis and (b) VUV/MnO₂ process (Fig.12).