Electrodeposition of Platinum Catalyst from Ionic Liquids

Abstract

Both battery and fuel cell electric vehicles are important building blocks for the transition to sustainable transportation [1]. Fuel cell vehicles have been introduced into the market, but have not yet reached a wide market penetration due to high cost and limited refueling infrastructure. One important cost factor is due to the large amounts of platinum required because of the sluggish kinetics of the oxygen reduction reaction (ORR) [1]. Currently, the main pathway for minimizing the Pt content consists in nanostructuring of Pt and especially by using Pt alloys. Electrodeposition is an effective pathway for the preparation of Pt nanoparticles. By choosing suitable electrolysis conditions one can control the morphology and the size of the obtained particles [2]. Electrodeposition of pure Pt can be accomplished in aqueous solutions [3]. However, aiming at Pt alloys with very reactive alloying elements requires a non-aqueous approach. Especially suitable are ionic liquids (ILs). The main advantages of ILs are a wide electrochemical window, low flammability, a nearly non-existing vapor pressure, and often low toxicity [4, 5]. The electrodeposition of Pt using standard Pt precursors from some ILs has been reported [6-8]. In this study, the deposition of platinum from PtCl4 dissolved in the IL 1-methyl-1-octylpyrrolidinium bis(trifluoromethylsulfonyl)imide (OMP TFSI) was explored on boron doped diamond (BDD) and Au electrodes for the electrochemical quartz crystal microbalance technique (EQCM) at 60 °C. A typical cyclic voltammogram on BDD is shown in Figure 1a. After pulsed electrodeposition (-1.6V vs Pt, 1s, 0V, 4s, 30 minutes total) and transfer of the washed electrode to 0.1 M H2SO4, a characteristic Pt voltammogram was obtained (Figure 1b). EQCM permitted to monitor directly changes in the resonance frequency and damping associated with the Pt(IV) reduction processes. Based on these results, the implications for alloy deposition and application to practical catalyst synthesis are discussed. The project leading to this abstract has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 700127. This Joint Undertaking receives support from the European Union’s Horizon 2020 Research and Innovation Programme and Hydrogen Europe and Hydrogen Europe Research. Figure 1. Cyclic voltammogram of a) BDD in 50 mM PtCl4 in OMP TFSI at 60°C, 20 mV s-1 b) BDD after Pt deposition in 0.1 M H2SO4, 100 mV s-1 References [1] O. Gröger, H. A. Gasteiger, J.-P. Suchsland, J. Electrochem. Soc., 162, A2605-A2622 (2015). [2] X. Zhang, F. Shi, X. Yu, H. Liu, Y. Fu, Z. Wang, L. Jiang, X. Li, J. Am. Chem. Soc., 126, 3064 (2004). [3] J.V. Zoval, J. Lee, S. Gorer, R.M. Penner, J. Phys. Chem. B, 102, 1166 (1998). [4] M.C. Buzzeo, R.G. Evans, R.G. Compton, ChemPhysChem, 5, 1106 (2004). [5] F. Endres, ChemPhysChem, 3, 144 (2002). [6] D. Zhang, W. C. Chang, T. Okajima, T. Ohsaka, Langmuir, 27, 14662-14668 (2011). [7] P. He, H. Liu, Z. Li and J. Li, J. Electrochem. Soc., 152, E146 (2005). [8] L. Asen, W. Ju, E. Mostafa, S. Martens, U. Heiz, U. Stimming, O. Schneider, ECS Trans., 75, 323 (2016). Figure 1