Citrate Effect on Reaction Kinetics of Pt Deposition on Pd(hkl) Via Surface Limited Redox Replacement of Cu UPD Monolayer

Wednesday, 27 May 2015: 10:20
PDR 4 (Hilton Chicago)
S. Brankovic, Q. Yuan (University of Houston), and M. Shao (The Hong Kong University of Science and Technology)
The effect of citrate ions in reaction solution on reaction kinetics of Pt deposition on Pd via SLRR of Cu UPD monolayer has been studied[i]. Experiments involving both, single crystal Pd and Pd-nanoparticle substrates were performed. The results suggest that citrate has a suppressive role on Pt deposition kinetics which is manifested through the zero order reaction kinetics during red-ox process[ii]. The citrate adsorbed phase on Pd surface has mainly transport hindering role for upcoming Pt ions. The IR data suggest that Pt monolayers produced from citrate containing electrolyte have weaker electrosorption ability for CO than bulk Pt and Pd. This information should be useful in further application of citrates as reactant and additive for Pt deposition via SLRR which can be used to fine tune Pt monolayer reactivity on different substrates[iii]. The reaction kinetics model was developed to analyze our kinetics data where the citrate effect was described as an extra barrier for the Pt ion transport. The model is capable of predicting the reaction rate constants from known concentrations of the citrate and platinum ions in the solution using only two model parameters, X and B3. Both parameters have the real physical meaning which could be directly visualized as the additional diffusion path for Pt ions due to the presence of adsorbed citrate layer on CuUPD/Pd-NP surface. The analytical work could be further applied in design and development of more sophisticated apparatus for Pt-shell Pd-core catalyst synthesis. This aspects will be discuss in the conclusion of the talk.

The authors acknowledge the private funding of this work and the support from NSF Chemistry division under the contract # 0955922.


[i]) S. R. Brankovic, J. X. Wang and R.R. Adzic, Surface Science, 474, L173 (2001).

[ii]D. Gokcen, S.-E. Bae, S.R. Brankovic, Electrochimica Acta, 56, 5545 (2011).  

[iii] S. R. Brankovic et al, submitted.