Photocatalyst

The anode is a critical component which determines the overall PFC performance. Both PC and FC reactions take place simultaneously at the anode. The photoanode is usually made by coating a thin layer of photocatalysts (e.g. Ti02, ZnO) onto an electrical conducting substrate. 

Many metal oxides and metal sulfides have been developed to be photocatalysts. Owing to its strong chemical stability, non-toxicity, and low cost, nano-crystalline titanium dioxide (Ti02) is 

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Heterogeneous Photocatalysis. Heterogeneous photocatalysis is a technology based on the irradiation of a semiconductor (SC) photocatalyst, for example, titanium dioxide [13463-67-7] Ti02, zinc oxide [1314-13-2] ZnO, or cadmium sulfide [1306-23-6] CdS. Semiconductor materials have electrical conductivity properties between those of metals and insulators, and have narrow energy gaps (band gap) between the filled valence band and the conduction band (see Electronic materials Semiconductors). 

Rapid e / h recombination, the reverse of equation 3, necessitates that D andM be pre-adsorbed prior to light excitation of the Ti02 photocatalyst. In the case of a hydrated and hydroxylated Ti02 anatase surface, hole trapping by interfacial electron transfer occurs via equation 6 to give surface-bound OH radicals (43,44). The necessity for pre-adsorbed D andM for efficient charge carrier trapping calls attention to the importance of adsorption—desorption equihbria in... 

Surface vs Solution Reactions, Anotliei issue of debate in pliotocatalyzed mineialization of oiganic substrates is whether the initial oxidation occurs on the photocatalyst s surface or in solution. Kinetic data of photooxidations and photoreductions have often been fitted to the simple... 

Inferences that oxidation takes place on the photocatalyst s surface have been made (67). No such conclusions can be drawn. Similar observations have been made in homogeneous media if a bimolecular reaction between two reactants is assumed. A Langmuir-type behavior is no guarantee of a surface occurring process. A rigorous treatment (68) of the kinetics involved in the photocataly2ed oxidations of organic substrates on an irradiated semiconductor has confirmed this. 

These photoinitiators or photocatalysts are usually added to the reactive coating formulations in concentration ranges from less than 1 to 20 wt % based on the total formulation. 

Tioxide process. This process is similar to that used to produce fumed silicas. Ultra-low particle size titanium dioxide (15-35 nm) is obtained for use as photocatalyst or UV absorber (for instance in sun protective creams). 

This photoinitiator (or photocatalyst) is composed of an electron relay system in which ruthenium bipyridyl... 

K.E. Karakitsou, and X.E. Verykios, Effects of altervalent cation doping of Ti02 on its performance as a photocatalyst for water cleavage, J. Phys. Chem. 97, 1184-1189 (1993). 

The challenges to be faced in air-purification systems using photocatalysis involve the treatment of relatively large gas flows in devices with low pressure drops, good catalyst irradiation, and efficient reactant species as well as good photocatalyst contacting [51-53]. 

Photocatalysts these harness energy from the sun to carry out chemical transformations. These energy-efficient catalysts are proving especially beneficial in destroying harmful waste and for water clean-up. 

Anoxic Hydrogen Production over CdS-based Composite Photocatalysts under Visible Light Irradiation (X, 420nm)... 

Table 1 Surface area, band gap energies and photocatalytic activities for H2 evolution from an electrolsde solution over single CdS and CdS-based composite photocatalysts.

Photocatalysts Surface area Bandgap Energy Ha evolution [pmolh ]... 

Fig.3 shows an effect of titanium dioxide loading on the decomposition of ethylene over a 20mesh wire-net photocatalyst. The decomposition rate increased in proportion to the amount of titanium dioxide loaded The specific initial rate (ro=(-dc/dt)t=o) was (1.8 0.2)x 10 ppm s g-catalysf. ... 

Initial cycle of irradiation on a wire-net photocatalyst Q 1st cycle A 2nd cycle V 3rd cycle 4th cycle... 

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