IJPAS Vol.03 Issue-01, (January, 2016) ISSN: 2394-5710 International Journal in Physical & Applied Sciences (Impact Factor- 2.865) A Monthly Double-Blind Peer Reviewed Refereed Open Access International e-Journal - Included in the International Serial Directories International Journal in Physical & Applied Sciences http://www.ijmr.net.in email id- irjmss@gmail.com Page 65 In situ surface-enhanced Raman spectroscopic studies of formic acid electrooxidation on Pt- modified Pd thin films deposited on silica core-gold shell nanoparticle arrays *Charles Kafui Dotse 1 and Shouzhong Zou 2 1 Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA 2 Department of Chemistry, American University, Washington, DC 20016, USA Abstract Surface-enhanced Raman spectroscopy (SERS) was used to study formic acid (FA) oxidation on trimetallic nanoparticles: Pt decorated Pd films on top of SiO 2 core gold-shell nanoparticles (SiO 2 @Au/Pd/Pt). The trimetallic nanoparticles showed high catalytic activity towards FA oxidation above 0.1 V vs Ag/AgCl as compared to SiO 2 @Au/Pd and SiO 2 @Au/Pt and the activity depends on the Pt coverage: the higher the Pt coverage, the lower the FA oxidation activity. The current studies augmented insight into electrocatalysis of FA oxidation and demonstrate the potential for multi- metallic nanoparticles in the design of catalysts for small organic molecules such as FA used in direct formic acid fuel cells (DFAFCs). Keywords: Formate, formic acid, palladium, platinum, surface-enhanced Raman spectroscopy, Under potential deposition. INTRODUCTION Formic acid is a liquid at room temperature and dilute concentrations of FA are listed on US Food and Drug Administration list of food additives as being safe(Yu and Pickup, 2008). Direct formic acid fuel cells (DFAFCs) have attracted much attention recently due to several advantages of using FA as the fuel over hydrogen or methanol. DFAFCs are less sensitive to fuel 'crossover', have fast oxidation kinetics, and have a much higher theoretical cell voltage than hydrogen fuel cell or direct methanol fuel cells (DMFCs)(Fang et al., 2011).Even though DFAFCs have a lower volumetric energy density (2104 WhL-1) than neat methanol in DMFCs (which is 4690WhL-1), this is compensated for by the use of higher concentration of FA and thinner membranes enabled by the lower fuel crossover effect(Yu and Pickup, 2008), (Jiang et al., 2014). The oxidation of FA takes place via a well-established dual pathway, namely the dehydrogenation (direct pathway) and dehydration (indirect pathway) ( Jiang et al., 2014). The direct pathway leads to the production of carbon dioxide (CO 2 ) from an active intermediate through simple decomposition of FA at open circuit or at high potentials via electrooxidation( Jiang et al., 2014). HCOOH → Active Intermediate → CO 2 + 2H + + 2e- (Electrooxidation) [1] → CO 2 + H 2 (Self dehydrogenation) [2] The indirect pathway, however, produces carbon monoxide (CO) which acts as a poison especially on Pt electrode surfaces thereby blocking active sites for dehydrogenation pathways at low potentials( Jiang et al., 2014). HCOOH → CO ad + H 2 O [3] Platinum and palladium-based catalysts are commonly used in DFAFCs. The effect of CO poisoning on Pt catalyst results in low efficiency and low power density (Arenz et al., 2003). Palladium on the other hand looks more attractive as a catalyst for FA oxidation via direct mechanism with limited poisoning effect. However, problems of low catalytic activity and /or instability of Pd-based catalyst are still issues of great concern (Jiang et al., 2014). Efforts are being made to address the above issues via developing new design of DFAFCs and screening of high efficiency anode catalysts. The use of nanoparticles with modified surfaces also exhibit high selectivity and reactivity than monometallic catalysts such as Pt and Pd. The trimetallic nanoparticles (Au, Pd, and Pt) even possess greater catalytic properties because more variables are available for tuning the activity. (Fang et al., 2011), (Arenz et al., 2003), (Du et al., 2011). Tian and coworkers (Fang et al., 2011) synthesized a new trimetallic nanoparticle (Au@Pd@Pt) which exhibited high catalytic activity