Intrinsic Photocatalytic Assessment of Reactively Sputtered TiO₂ Films

Abstract

Thin TiO2 films were prepared by DC magnetron reactive sputtering at different oxygen partial pressures. Depending on the oxygen partial pressure during sputtering, a transition from metallic Ti to TiO2 was identified by spectroscopic ellipsometry. The crystalline nature of the film developed during a subsequent annealing step, resulting in thin anatase TiO2 layers, displaying photocatalytic activity. The intrinsic photocatalytic activity of the catalysts was evaluated for the degradation of methylene blue (MB) using a microfluidic reactor. A numerical model was employed to extract the intrinsic reaction rate constants. High conversion rates (90% degradation within 20 s residence time) were observed within these microreactors because of the efficient mass transport and light distribution. To evaluate the intrinsic reaction kinetics, we argue that mass transport has to be accounted for. The obtained surface reaction rate constants demonstrate very high reactivity for the sputtered TiO2 films. Only for the thinnest film, 9 nm, slightly lower kinetics were observed.

Photocatalytic Properties of Doped TiO2 Coatings Deposited Using Reactive Magnetron Sputtering

“…The photocatalytic efficiency of the surfaces was evaluated from the decay in the absorbance peak using the slope of line ln(A 0 /A) vs. time. Table 4 presents the rate constant, k a , and the surface-normalised rate constant, k" [31]. Rafieian et al [31] collated k" values for MB degradation in the presence of TiO 2 prepared using various sputtering methods.…”

“…Table 4 presents the rate constant, k a , and the surface-normalised rate constant, k" [31]. Rafieian et al [31] collated k" values for MB degradation in the presence of TiO 2 prepared using various sputtering methods. The reported k" values range between 7.99 × 10 −8 and 2.87 × 10 −6 m s −1 .…”

“…The rate constant should be normalised to take into account both the volume of the MB solution and the surface area of the substrate. The surface normalised rate constant, k" was calculated by multiplying ka with the reactor volume to catalyst area ratio [31].…”

Designing Microflowreactors for Photocatalysis Using Sonochemistry: A Systematic Review Article

“…Thus, Matsushita et al have developed photocatalytic microreactors with an immobilized TiO 2 layer [74]. The thermal oxidation [75], physical vapor deposition (PVD) [76], chemical vapor deposition (CVD) [77,78], dip-coating [79], spin-coating [80], electrospun [81], sputtering [82], sol-gel [83], and electrodeposit [84] methods are techniques for the film formation step needed in the design of immobilized photoreactors. Figure 9 represents a sol-gel-based deposition of TiO 2 inside a glass microtube.…”

Investigation of the reaction kinetics of photocatalytic pollutant degradation under defined conditions with inkjet-printed TiO2 films – from batch to a novel continuous-flow microreactor

“…25,41 Kinetic studies can also be found for microreactors with immobilized photocatalyst. 24,42,43 For microreactors, although external mass transport limitations are often considered (see, e.g., ref. 44), internal (pore) diffusion limitations are not always discussed.…”