Platinum composite electrodes fabrication

For fabrication of a full plastic DSSC, the plastic counter electrode needs to show high performance in keeping with a high-density photocurrent, with characteristics close to those of a platinum counter electrode. 1-V characteristics of plastic DSSCs have been examined. An electrolyte composition of 0.4M Lil, 0.4M TBAI, 0.04M I2, and 0.3 M N-methylbenzimidazole (NMB) in acetonitrile (AN)/MPN (1 1 by volume) was used and N719 as a dye sensitizer of the Ti02 photoanode the 1-V curves are compared in Figure 3.7 for PEDOT-PSS-based counter electrodes and a standard platinum sputtered electrode [29]. 

Electrochemical oxidation of methanol is important for application in direct methanol fuel cells. Among metal catalysts, platinum is generally used as an electrocatalyst for such an oxidation. However, it suffers from poisoning by CO, formed as a by-product, and other adsorbed species. A promising way to enhance electrocatalytic activity of Pt and reduce its poisoning effect is to fabricate conducting polymer/Pt composite electrodes. 

Most biosensors described in the literature for the determination of urea are potentiometric based on NH4 or HCOj" sensitive electrodes [181, 182]. Osaka and co-workers constructed a highly sensitive and rapid flow injection system for urea analysis with a composite film of electropolymerised inactive PPy and a polyion complex [183]. Pandey and co-workers fabricated a urea biosensor based on immobilised urease on the tip of an ammonia gas electrode (diameter 10 pm) made from a PPy film coated onto a platinum wire [170]. The enzymatic response was achieved in the wide range of 0.001-0.05 M with a stability of more than 32 days. Cho and co-workers [184] developed a procedure for urea determination by crosslinking urease onto PANI-Nafion composite electrodes, which could sense the ammonium ions efficiently. Such a urea biosensor has a detection limit of about 0.5 pM and a response time of 40 seconds. 

Wang J, Swain GM. Fabrication and evaluation of platinum/diamond composite electrodes for electrocatalysis. J Electrochem Soc 2003 150 E24-32. 

The described impregnation-reduction steps are typically repeated 1-3 times in order to increase the thickness and electric conductivity of the electrodes. The third step is the secondary plating (or surface electroding) process to deposit additional Pt at the outer surface of the electrode to further increase the electrode surface conductivity. The composite is immersed in the Pt complex solution, and by using reducing agents such as hydroxylamine hydrochloride and hydrazine monohydrate, the platinum is deposited on the top of the initial Pt electrode layer. A detailed description of the fabrication process can be found in (Kim and Shahinpoor 2003). 

Platinum ceramic composites as new electrode materials fabrication, sintering, microstructure and properties, J. Rager, A. Nagel, M. Schwenger, A. Flaig, G. Schneider, and F. Miicklich, Advanced Engineering Materials, 2006, 8, 81. 

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