Catalyst coating electrophoretic deposition

The activities of CNTs have been evaluated by Girishkumar et al. [7] using ex situ EIS. Their study was conducted in a three-compartment electrochemical cell using a GDE electrode (a carbon fibre paper coated with SWCNTs and Pt black as an anode or cathode). Electrophoretic deposition was used to deposit both the commercially available carbon black (CB) for comparison and the SWCNT onto the carbon Toray paper. Commercially available Pt black from Johnson Matthey was used as the catalyst. In both cases, the loading of the electrocatalyst (Pt), the carbon support, and the geometric area of the electrode were kept the same. EIS was conducted in a potentiostatic mode at either an open circuit potential or controlled potentials. 

Similarly, catalyst coatings can be used to produce MSs via thin film gas phase deposition, with chemical (up to 10 pm thickness) and physical vapour deposition methods (< 1 pm) typically used to deposit metals and metal oxide thin-fihns. Other methods such as electrophoretic deposition of alumina, ZnO, Ce02 and Zr02 coating layers inside the microreactors are also used (Cybulski and Moulijn, 2006 Hessel et al., 2005c). 

Fig. 8. Schematic of a catalyst coating apparatus for electrophoretic deposition or anodic oxidation inside assembled microreactors.

Electrophoretic deposition is a colloidal process used to coat either aluminium or stainless steel [122]. Either adhesion layers or complete coatings can be achieved. To-date mainly alumina suspensions have been used for electrophoretic deposition. Wunsch et al. coated microchannels with alumina nanopartides dissolved in oxalic add and mixed with alumina gd or glycerol [124] 2-4 pm thick adhesion layers were formed. Fbdisdi et al. applied dectrophoretic predpitation of industrial catalyst powders at 100 V (dc) [140]. After 2 min a uniform deposition of the catalyst powder on the surface was achieved. 

Another possibility of ceramic material application is the use of coatings and foams inside, for example, metallic microstructure devices. Here, well-known technologies such as CVD processes, sputtering, electrophoretic deposition, sol-gel methods in combination with spin coating, dip coating, or wash coating methods, or the use of anodic oxidation for aluminum-based devices will lead to either dense, protective ceramic coatings or porous layers used as catalyst support. 

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