Yoshiyuki Teramoto

Activation of graphitic carbon nitride (g-C3N4) by alkaline hydrothermal treatment for photocatalytic NO oxidation in gas phase

Photocatalytic activity of graphitic carbon nitride (g-C3N4) was significantly improved by an alkaline hydrothermal treatment. The specific surface area of g-C3N4 obtained by heating melamine at 550 °C was only 7.7 m2 g−1, which was too small for it to be utilized as a catalyst for air purification. By the hydrothermal treatment with NaOH solution at 90–150 °C, the surface area was increased up to 65 m2 g−1, and the oxidation rate of nitrogen oxide (NO) under visible light (380 < λ < 480 nm) was increased by 8.6 times. XRD, ESR, elemental analysis and electron microscopy showed that unstable domains of not-well-ordered carbon nitride were removed by hydrolysis to form a mesoporous structure with a higher surface area. Deactivation of g-C3N4 was not observed during the experimental period, although a small part of carbon nitride was decomposed by self-oxidation.

Plasma Catalysis for Environmental Treatment and Energy Applications

The current status of plasma-catalysis research and the associated possible applications are outlined. A basic explanation of plasma chemistry is given, which is then used as a foundation to indicate the research vector for the ongoing development of various applications. As an example of an environmental application, volatile organic compound decomposition using plasma-catalysis is discussed in depth, from the fundamental concept to the current industrial application status. As a potential application of plasma-catalysis towards the realization of a future “hydrogen society”, ammonia synthesis is discussed in terms of current social attitudes and regulations, along with historical developments. Additionally, up-to-date information on the fundamentals of the nonthermal plasma interaction with a catalyst is provided.

Study of Plasma-Induced Surface Active Oxygen on Zeolite-Supported Silver Nanoparticles

Surface oxygen induced by non-thermal plasma at atmospheric pressure on silver nanoparticle-loaded zeolite was determined by a chemical probe based on the oxidation of NO. The amount of active oxygen fixed onto the catalyst surface by O2 plasma was approximately proportional to the square of the amount of supported silver. In dry air, its extraordinary long lifetime was confirmed for the first time.Graphical Abstract

Ozone-Assisted Catalysis of Toluene with Layered ZSM-5 and Ag/ZSM-5 Zeolites

This paper presents a new type of ozone-assisted catalysis for toluene decomposition. The different catalytic activities of ZSM-5 and Ag/ZSM-5 were incorporated into a layered catalyst with a tandem configuration. Instead of increasing the amount of metal catalyst, the layered catalyst was formed, which had an equal amount of bare ZSM-5 and Ag/ZSM-5 and could achieve both high toluene conversion and CO2 selectivity concurrently. The properties of each catalyst were evaluated with respect to toluene conversion, formation of intermediates, CO2 selectivity and ozone demand factor. The bare ZSM-5 exhibited higher toluene conversion than the Ag/ZSM-5, while its activity toward deep oxidation was limited. However, the Ag/ZSM-5 was found to be effective for the deep oxidation of reaction intermediates (HCOOH and CO). Separate oxidation tests with HCOOH and CO revealed that the ZSM-5-supported Ag nanoparticles could oxidize the HCOOH and CO in the absence of ozone, which was not possible with the bare ZSM-5. Plausible pathways for the oxidation of toluene with O3 over ZSM-5 and Ag/ZSM-5 were proposed based on the experimental evidence.

Effect of Catalyst Type on Optical Emission

The effect of catalyst types on optical emission was studied in N2 discharge under atmospheric pressure. In silver nanoparticle-loaded MS-13X and HY, purple emissions were observed. On the other hand, green emission was observed in silver nanoparticle-loaded HY. This spectrum had a broadband around 540 ± 60 nm. It may be firescence from excited silver on catalyst surface. When toluene adsorbed onto Ag/HY, emission color changed from green to purple in adsorption area only. After catalyst regeneration by O2 plasma treatment, the emission color returned to green. There, interesting phenomena were important to figure out the mechanism of plasma-catalyst hybrid technology.

Indirect Synthesis System for Ammonia from Nitrogen and Water Using Nonthermal Plasma Under Ambient Conditions

The indirect synthesis of NH3 from N2 and H2O through plasma processing is proposed and demonstrated. NH3 is a promising hydrogen storage material because of its high hydrogen storage density. Mg3N2 is a key material for indirect NH3 synthesis, because the reaction of Mg3N2 with water easily generates NH3 at room temperature. In this paper, therefore, we focus on generating Mg3N2 by nitridation of MgO with nonthermal atmospheric-pressure dielectric barrier discharge (DBD) plasma in a N2 atmosphere. By intermittent DBD nitridation treatment while the reaction device was cooled in a water bath, a maximum Mg3N2 generation efficiency of 93xa0mg/kWh was estimated. Because NH3 is generated through a simple chemical reaction, our scheme does not cause NH3 decomposition by plasma, which is one of the greatest concerns associated with plasma synthesis. Contrary to the conventional NH3 generation process, which emits CO2 and requires high temperature and pressure, our scheme enables NH3 synthesis from N2 and H2O without CO2 emissions. This allows for an onsite small-scale NH3 synthesis system to be realized under mild conditions, which is necessary for a future low-carbon society.