Deep Oxidation of NO by a Hybrid System of Plasma–N-Type Semiconductors: High-Energy Electron-Activated “Pseudo Photocatalysis” Behavior

Abstract

A "pseudo photocatalysis" process, being initiated between plasma and N-type semiconductors in the absence of light, was investigated for NO removal for the first time via dynamic probing of reaction processes by FT-IR spectra. It was demonstrated that N-type semiconductor catalysts could be activated to produce electron-hole (e-h) pairs by the collision of high-energy electrons (e*) from plasma. Due to the synergy of plasma and N-type semiconductors, major changes were noted in the conversion pathways and products. NO can be directly converted to NO and NO instead of toxic NO, owing to the formation of O and ·OH present in catalysts. New species like O or ·O may be generated from the interaction between catalyst-induced species and radicals in plasma at a higher SIE, leading to deep oxidation of existing NO to NO. Experiments with added trapping agents confirmed the contribution of e and h from catalysts. A series of possible reactions were proposed to describe reaction pathways and the mechanism of this synergistic effect. We established a novel system and realized an e*-activated "pseudo photocatalysis" behavior, facilitating the deep degradation of NO. We expect that this new strategy would provide a new idea for in-depth analysis of plasma-activated catalysis phenomenon.

Synergistic effects of crystal structure and oxygen vacancy on Bi2O3 polymorphs: intermediates activation, photocatalytic reaction efficiency, and conversion pathway

“…In the past decade, photocatalysis as a green technology has received increased attention since its diverse applications in environmental remediation and solar energy conversion [1][2][3][4]. Generally, the photocatalytic efficiency involves three aspects: (1) the light absorption ability of photocatalyst [5]; (2) the separation and transportation efficiency of charge carriers [6,7]; (3) the redox reaction associating with photo-induced reactive radicals [8][9][10]. Therefore, comprehensive catalyst design in terms of visible-light utilization, charge carrier separation, and redox capacity of reactive radicals is essential and urgent for achieving highly efficient photocatalytic efficiency [11][12][13].…”

“…Linsebigler et al [13] reported that anatase TiO 2 exhibited much higher photocatalytic activities than that of rutile TiO 2 , resulting from the differences among optical properties, band gap, and the recombination rate of charge carriers of the polymorph [16]. Also, crystal structure has been demonstrated to have crucial effect on many kinds of photocatalysis (such as Ga 2 O 3 [11], WO 3 [17], Bi 2 O 3 [18], BiPO 4 [19], etc. ).…”

In-plasma-catalysis for NOx degradation by Ti3+ self-doped TiO2−x/γ-Al2O3 catalyst and nonthermal plasma

“…Previous researchers 47 have pointed out that the intensity of ultraviolet rays generated during the plasma discharge process is basically insufficient to excite the photocatalytic process. Meanwhile, Chen et al 23 believed that one of the key factors in the process of plasma-assisted N-type semiconductor catalysis was the forbidden band width of the catalyst. Thus, TiO 2− x has a lower forbidden band gap that positively accelerates the catalysis process of the plasma-assisted N-type semiconductor.…”

“…TiO 2 is regarded as a promising N-type semiconductor catalyst for industrial applications using photocatalysis due to its advantages of low-toxicity, chemical and thermal stability, and corrosion resistance. 21,22 Chen et al 23 revealed the relationship between the band gap of an N-type semiconductor and the NO x degradation efficiency in the process of DBD (Dielectric Barrier Discharge) synergistic catalytic oxidation to remove NO x , thus it is very important to nd a simple and effective modication method for TiO 2 . Recently, hydrogenated black titanium dioxide [24][25][26] has aroused widespread research interest due to its narrow band gap and high-efficiency full-spectrum response characteristics.…”

Synergetic effect between non-thermal plasma and photocatalytic oxidation on the degradation of gas-phase toluene: Role of ozone

“…Emissions of volatile organic compounds (VOCs) are an important cause of air pollution, not only harming the human health and the ecological environment directly, but also leading to the formation of PM2.5, ozone, and photochemical smog [1][2][3][4]. Advanced oxidation processes such as thermal catalytic oxidation [5][6][7], non-thermal plasma (NTP) [8][9][10][11][12][13], and photocatalytic oxidation (PCO) [14][15][16][17][18] have been deemed efficient technologies for air purification. Although NTP technology exhibits high efficiency with regard to the removal of VOCs with a short residence time and relatively low energy consumption, it also suffers from the disadvantages of low selectivity in the mineralization of VOCs and the generation of undesirable by-products such as ozone [8,14].…”