Computational study of TiO₂ Brookite (100), (010) and (210) surface doped with Ruthenium for application in Dye Sensitised Solar Cells

Abstract

Abstract. Titanium dioxide (TiO2) polymorphs are widely used in many energy-related applications due to their peculiar electronic and physicochemical properties. The electronic structures of brookite TiO 2 surfaces doped with transition metal ruthenium have been investigated by ab initio band calculations based on the density functional theory with the planewave ultrasoft pseudopotential method. The generalized gradient approximation (GGA) was used in the scheme of Perdew-Burke-Ernzerhof (PBE) to describe the exchange-correlation functional. All calculations were carried out with CASTEP (Cambridge Sequential Total Energy Package) code in Materials Studio of Accelrys Inc. The surface structures of Ru doped TiO 2 were constructed by cleaving the 1 × 1 × 1 optimized bulk structure of brookite TiO2. The results indicate that Ru doping can narrow the band gap of TiO2, leading to the improvement in the photoreactivity of TiO2, and simultaneously maintain strong redox potential. The theoretical calculations could provide meaningful guide to develop more active photocatalysts with visible light response. IntroductionIn the last decades, properties for titanium dioxide (TiO 2 ) polymorphs have been the subject of many experimental and computational studies, the most common polymorphs being the minerals rutile, anatase, and brookite [1]. A large number of applications of TiO 2 in materials science is, almost without exception, ultimately a result of the facile electron-transfer processes that occur at the interface between the semiconductor and adsorbed molecules [1][2][3][4][5][6][7]. When photons are excited, TiO 2 is a good electron and hole donor and can, therefore promote photocatalytic processes at its interface [3]. Its photocatalytic properties, in addition to its abundance, low cost, stability, and low toxicity, are the basis for its use in solar cells [4]. However, brookite is the rarest of the natural occurring TiO 2 polymorphs, and it is the most difficult phase to prepare in the laboratory [1]. As a result, the properties of pure brookite are poorly known. TiO 2 can only show photocatalytic activity under ultraviolet (UV) light irradiation (λ < 387.5 nm) that accounts for only a small portion of solar energy (approximately 5%), in contrast to visible light for a major part of solar energy (approximately 45%), but can be photosensitized by the adsorption of chromophores that, when excited, inject electrons into the TiO 2 conduction band [8]. In spite of a large number of publications on pure and doped TiO 2 many aspects of

DFT study of TiO2 brookite (210) surface doped with silver and molybdenum

“…Gong and Selloni did a first principle study of different surfaces of brookite, reporting that while the structure of brookite TiO 2 (210) surface is close to that of the most stable anatase TiO 2 (101) surface, the former has high chemical reactivity [31]. Previous studies investigated the factors affecting the photocatalytic activity of TiO 2 when doped with transition metals [33][34][35][36][37][38][39][40][41][42]. Another study investigated the change in the activity of the photocatalytic properties of rutile and anatase polymorphs of nanocrystalline TiO 2 doped with transition metals; namely Cu, Fe, Co, and Cr [43].…”

Electronic, Structural, and Optical Properties of Mono-Doped and Co-Doped (210) TiO2 Brookite Surfaces for Application in Dye-Sensitized Solar Cells—A First Principles Study

“…In the DSCCs, the TiO 2 semiconductor is very important for the efficiency of the cell as the dye molecules adsorb on its surface. The dye molecules are used for the photonadsorption and they are the source of the photocurrent of the solar cells [ 3 , 4 , 5 , 6 ]. However, the electron band gap of TiO 2 is relatively large (3.2 eV for anatase, 3.0 eV for rutile and 3.4 eV for brookite) [ 7 , 8 , 9 , 10 ].…”

“…Improving the visible light response of oxide semiconductor materials by reducing the band gap energy has become a universal research focus in the photocatalytic field using both experimental and theoretical techniques. Although TiO 2 is an attractive semiconductor for DSCCs, it can only make use of less than 5% of the solar spectrum in its pristine state owing to its large band gap [ 1 , 6 , 7 , 8 , 10 ].…”