Microwave-Hydrogen-Plasma-Assisted Synthesis of Black Titania as Photocatalyst in Photodegradation of Rhodamine B
Muhamad Nur Siddik(a,b), Ilham(a), Muhammad Fadhil Rizki(a), Didi P. Benu(a,c), Fry V. Steky (a), Kemal L.H. Putra (a), Fairuz G. Nugroho(d,e), Veinardi Suendo(a,e*).

(a) Inorganic and Physical Chemistry Research Division, Departement of Chemistry, Institut Teknologi Bandung, Bandung 40132, Indonesia.

(b) Science Faculty, Universitas Islam Negeri Sultan Maulana Hasanuddin, Banten 42118, Indonesia.

(c) Departement of Chemistry, Universitas Timor, Kefamenanu 85613, Indonesia.

(d) Master^s Program in Nanotechnology, Graduate School, Institut Teknologi Bandung, Bandung 40132, Indonesia.

(e) Research Center of Nanoscience and Nanotechnology, Institut Teknologi Bandung, Bandung 40132, Indonesia.

*)E-mail address: vsuendo[at]chem.itb.ac.id

Abstract

The application of titania as a photocatalyst under sunlight is well-known to be an inefficient process. TiO2 large band gap makes it less sensitive to light in the visible-NIR region. Black TiO2 receives much attention from researchers due to its narrower band gap and higher sensitivity to light in the visible-NIR region than that of TiO2. Synthesis of black TiO2 using microwave-assisted hydrogen plasma is an effective and efficient method due to its simple and rapid preparation. Our goals are to fabricate a microwave-assisted hydrogen plasma reactor, to study the relation between black TiO2 synthesis time and its physicochemical properties, and to study the photocatalytic activity of prepared black TiO2. The capability of the plasma reactor to generate reactive hydrogen species is measured using OES (optical emission spectroscopy) technique. TiO2 pellets press with 2.5 metric-ton for 5 minutes and then treated in the plasma reactor. Raman Spectroscopy is used to study the chemical structure and polymorphism of the plasma-treated TiO2. Band gap, sensitivity towards UV-Visible region, and relative amount of defects of plasma-treated TiO2 are characterized using UV-Vis DRS. Photoluminescence spectroscopy was carried out to reveal the relative amount of the radiative-recombined defect, a kind of defect related to the photocatalytic activity of plasma-treated TiO2. Microwave-assisted hydrogen plasma reactor was successfully fabricated and able to generate three kinds of hydrogen radiative transitions: H&#945- (21%), H&#946- (8.4%), and H2Fulcher-&#945- (70.6%). Black TiO2 was successfully synthesized with the darkest TiO2 prepared in 3 h of plasma treatment. Hydrogen plasma treatment can create new electronic states, initiate phase transition from anatase to rutile, create defects, narrow the band gap, and enhance sensitivity towards visible light. Here, 1h of plasma treatment provides the leading photocatalytic activity in the photodegradation of rhodamine B at &#955- = 405 nm with k = 3.17x10-3 s-1 and Ea = 11.62 kJ/mol.

Keywords: Black TiO2, Microwave-Assited Hydrogen Plasma, Photocatalyst, Photodegradation Kinetics, Reactive Hydrogen Species, Titania

Topic: CHEMISTRY AND MATERIAL SCIENCES