Three-dimensional hollow urchin α-MnO2 for enhanced catalytic activity towards toluene decomposition in post-plasma catalysis

Abstract

Complete oxidation of volatile organic compounds (VOCs) with high energy efficiency remains a challenge in post-plasma catalysis (PPC) due to insufficient adsorption towards gas and relatively low catalytic activity at room temperature. Three-dimensional (3D) hollow urchin α-MnO2 for post-plasma catalytic decomposition of toluene is demonstrated in this study. Hollow urchin catalyst assembled by well-defined one-dimensional (1D) α-MnO2 nanorods is prepared by a simple one-step hydrothermal method without any template. The toluene decomposition, CO2 selectivity and carbon balance over hollow urchin α-MnO2 reach up to ~100%, ~59% and ~81% at an SIE of 240 J L−1, which are 43%, 96% and 44% superior to that of non-thermal plasma (NTP) process, respectively. The combination of NTP with hollow urchin α-MnO2 also significantly promotes the energy efficiency by 64%, reaching 13.1 g kWh−1 at an SIE of 119 J L−1. Moreover, hollow urchin α-MnO2 exhibits higher catalytic activity for toluene decomposition and ozone conversion compared with solid urchin α-MnO2. The hollow structure with an enlarged contact surface area is expected to enhance adsorption towards gas and prolong the retention of gas on the catalyst surface. Furthermore, the fully exposed non-agglomerated 1D α-MnO2 nanorods can promote oxygen vacancy density and low-temperature reducibility, facilitating the adsorption and conversion of ozone into active oxygen species (~100% ozone conversion), which leads to the deep decomposition of toluene in PPC. This work explores a new concept in designing 3D hollow urchin nanoarchitecture as a novel catalyst for efficient plasma-catalytic gas purification.