Formic acid oxidation on Pt–Au nanoparticles: Relation between the catalyst activity and the poisoning rate

• Published in: Journal of power sources 2012-01, Vol.197, p.72-79
• Main Authors: Obradović, M.D., Rogan, J.R., Babić, B.M., Tripković, A.V., Gautam, A.R.S., Radmilović, V.R., Gojković, S.Lj
• Format: Article
• Language: English
• Subjects: Applied sciences; Catalysis; Catalysts; Catalysts: preparations and properties; Chemistry; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Formic acid electrooxidation; Fuel cell; Fuel cells; General and physical chemistry; Gold; Nanoparticles; Oxidation; Platinum; Precursors; Reduction; Surface chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2011.09.043

► Two methods of Pt–Au nanoparticles preparation were applied. ► High dispersion of Pt on Au nanoparticles is necessary for the direct oxidation of HCOOH. ► Severe electronic modification of Pt by Au can induce deactivation of the catalyst. Pt–Au nanoparticles supported on high area carbon were prepared by simultaneous reduction of Au and Pt precursors and by reduction of Pt precursor on already prepared Au nanoparticles. The first method produced a solid solution of Pt in Au containing ∼5% Pt with the remaining Pt on the nanoparticles’ surface. For the Pt:Au precursor ratio of 1:4 and 1:9, the surface ratio was found to be 0.70:0.30 and 0.55:0.45, respectively. By the second method with the Pt:Au precursors ratio of 1:12, the surface ratio was 0.30:0.70. The voltammetric peaks of Pt–oxide reduction and COads oxidation demonstrated electronic modification of Pt by Au in all catalysts. With decreasing Pt:Au surface ratio the activity for HCOOH oxidation increases and surface coverage by COads decreases. The highest activity under potentiodynamic and quasi steady-state conditions without poisoning by COads was observed for the catalyst with the lowest Pt:Au surface ratio. Chronoamperometic test showed that its high catalytic activity is associated with a high deactivation rate. It was postulated that too strong adsorption of a reactive or non-reactive intermediate caused by electron modification of Pt by underlying Au, is responsible for the deactivation. This result stresses that high Pt dispersion, necessary for promotion of the dehydrogenation path in HCOOH oxidation, can produce too strong adsorption of intermediates causing deactivation of the catalyst.