Apply copper-oxides-compositing TiO2 photocatalyst probes to photoelectrocatalytic water splitting reactions under illumination of visible light

• Main Authors: Fu-chieh Hsieh, 謝富傑
• Other Authors: Chung-Hsuang Hung
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/07555092987739922536

碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程研究所 === 100 === The objective of this study to conduct photoelectrocatalytic (PEC) water splitting reactions by using titanium dioxide (TiO2) thin film probes under illumination both near-UV and visible light sources. The TiO2 thin film probes were prepared by compositing TiO2 with copper oxides via magnetron sputtering processes. Several operation parameters including solution pH levels, types and concentrations of electrolytes, applied external bias intensity, and types of irradiated light sources were examined in the study. Both hydrogen yielded rate and photocurrent density were measured for determining the activities of the prepared samples. Some important results were achieved in the study: Apparent "red shift" effects were observed for the TiO2 catalysts composed with copper oxide (TNCu5, TNCu15). The light absorption wavelength has been shifted to from UVA (~ 380 nm) to the blue visible light (600~750 nm). The estimated band gap energy of the prepared samples ranged from 1.7 to 2.0 eV. The XRD phases show the preferred orientation of the preferred angle and direction of the copper-oxide crystals, which are2?僯 25.26°(101) for anatase crystalline and 2θ= 36.41° (111) for Cu2O. Linear cyclic voltammetry scanning results confirmed the production of photocuurent while the probes irradiated with both simulated solar light and near-UV light (?軯 365 nm), and by LED visible light (?軯 470 nm) especially. The water splitting capability of TiO2 was enhanced after compositing copper oxides, too. It was also observed that both photocuurent density and H2 yield rate increased with applied bias and water solution pH levels. For the H2 production, other than the illumination of both near-UV and simulated solar light, the prepared TiO2/Cu2-xO probes also had the capability of splitting water to hydrogen by using LED blue light as a light source, indicating that they are visible light responsible photocatalysts. Under the illumination of the LED blue light, a H2 production rate of 9.6 × 10-4 mole/cm2 hr was achieved while a bias voltage of 1.5 V applied. In addition, for the effects of electrolyte types on the H2 production, the production rate had a order of Na2S+K2SO3 , Na2SO4 , and Na2CO3. Being as a sacrifice reagent, Na2S coupling K2SO3 had the highest hydrogen production rate of 1.92×10-3 mole/cm2 hr. The recombination rate of photo-generated electrons and holes was retarded may be the main reason. Besides, in the study, the measurements of Mott-Schottky effects and flat band potential of the PEC system were applied for evaluating the photocatalytic activity of the prepared samples. The results confirmed that the prepared TiO2 probes achieved more efficient electrons transferred from semiconductor to water because they worked like p-n diode semiconductors.