Since the water splitting reaction using semiconductor electrode reported by Fujishima et al. in 1972 [1], there is increasing interest in the development of metal oxide photocatalysts for environmentally friendly applications such as air purification [2], hydrogen production via water splitting [3] and the removal of organic molecules from water [4]. Recently, photocatalyst thin film has aroused growing interests instead of a powder type of photocatalyst. Photocatalyst film can be deposited on various substrate such as alumina [5], metal foil [6], silicon wafer [7,8], and glass [9,10]. Among these substrates, the glass can be advantageous in various fields owing its high transmittance and chemical stability. The glass coated with photocatalyst
…show more content…
However, TiO2 is only sensitive to UV light region, because of its large band gap (~3.2 eV) [13], and fast recombination of electron/hole pair limits its photocatalytic reaction process [14]. Many attempts have been devoted to develop high-performance TiO2 photocatalysts for practical applications such as core–shell structure [15] nonmetal or metal doping [16–19], phase mixing [20,21], generation of oxygen vacancy [22], and coupling with other semiconductors [23–28]. In particular, coupling with another semiconductor has been widely used to improve the photoelectrochemical and photocatalytic performance of TiO2 materials. WO3 is a suitable species, because of its relative small band gap and acidic surface, and therefore it can serve as a sensitizer and electron-accepting agent in TiO2/WO3 heterostructured form …show more content…
Hydrochloric acid (HCl, 37%, Sigma-Aldrich®) and nitric acid (HNO3, 70%, Sigma Aldrich®) were added to the solution to inhibit the precipitation of the solution by controlling the hydrolysis and condensation reactions. Based on the TTIP content, HCl was added in the molar ratio of 0.09 (TWCl), and HNO3 was in the molar ratio of 0.09 (TWN1) and 0.15 (TWN2), respectively. These solutions were aged for 24 h before spin coating treatment to improve film quality. The SiO2 solution was also prepared by mixing ethanol, deionized water, tetraethyl orthosilicate (TEOS, 99%, Sigma-Aldrich®), and HCl in the molar ratio of 10:4:1:0.03 for introducing SiO2 barrier layers onto soda-lime glass substrates. The TiO2/WO3 and SiO2 solutions were stable and transparent for two weeks without precipitation at room
However, TiO2 is only sensitive to UV light region, because of its large band gap (~3.2 eV) [13], and fast recombination of electron/hole pair limits its photocatalytic reaction process [14]. Many attempts have been devoted to develop high-performance TiO2 photocatalysts for practical applications such as core–shell structure [15] nonmetal or metal doping [16–19], phase mixing [20,21], generation of oxygen vacancy [22], and coupling with other semiconductors [23–28]. In particular, coupling with another semiconductor has been widely used to improve the photoelectrochemical and photocatalytic performance of TiO2 materials. WO3 is a suitable species, because of its relative small band gap and acidic surface, and therefore it can serve as a sensitizer and electron-accepting agent in TiO2/WO3 heterostructured form …show more content…
Hydrochloric acid (HCl, 37%, Sigma-Aldrich®) and nitric acid (HNO3, 70%, Sigma Aldrich®) were added to the solution to inhibit the precipitation of the solution by controlling the hydrolysis and condensation reactions. Based on the TTIP content, HCl was added in the molar ratio of 0.09 (TWCl), and HNO3 was in the molar ratio of 0.09 (TWN1) and 0.15 (TWN2), respectively. These solutions were aged for 24 h before spin coating treatment to improve film quality. The SiO2 solution was also prepared by mixing ethanol, deionized water, tetraethyl orthosilicate (TEOS, 99%, Sigma-Aldrich®), and HCl in the molar ratio of 10:4:1:0.03 for introducing SiO2 barrier layers onto soda-lime glass substrates. The TiO2/WO3 and SiO2 solutions were stable and transparent for two weeks without precipitation at room