Contribution of Electrocatalyst Support to PEM Oxidative Degradation in an Operating PEFC. Issue 14 (30th November 2016)

• Record Type: Journal Article
• Authors: Prabhakaran, Venkateshkumar; Wang, Guanxiong; Parrondo, Javier; Ramani, Vijay
• Is Part Of: Journal of the Electrochemical Society. Volume 163:Issue 14(2016)
• Page Start: F1611
• Page End: F1617
• Publication Date: 2016-11-30
• Subjects: catalyst support -- Fuel cells -- In-situ fluorescence spectroscopy -- PEM degradation -- ROS/H2O2 generation; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.1311614jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : The contribution of the electrocatalyst support to polymer electrolyte membrane (PEM) oxidative degradation in an operating polymer electrolyte fuel cell was investigated. A corrosion-resistant non-carbon catalyst support based on mixed ruthenium and silicon oxides (RuO2 -SiO2 ; RSO) was compared against a benchmark carbon-based support (Vulcan XC 72; C). The rates of in-situ reactive oxygen species (ROS) generation (Pt/C: 9.0 ± 0.20 × 10 −5 s −1 ; Pt/RSO: 5.9 ± 0.19 × 10 −5 s −1 ) and macroscopic PEM degradation measured ex-situ as the fluoride emission rate (FER; Pt/C: 2.7 ± 0.32 × 10 −5 ppm cm −2 s −1 ; Pt/RSO: 2.5 ± 0.31 × 10 −5 ppm cm −2 s −1 ) were significantly lower for platinum supported on RSO than for platinum supported on carbon. There was an excellent correlation between the in-situ ROS generation rate and the FER, thereby confirming the causal relationship between ROS generation and PEM degradation. The lower rate of ROS generation over RSO and Pt/RSO was attributed to a lower net rate of electrochemical H2 O2 generation during the oxygen reduction reaction (ORR). Rotating ring-disk electrode experiments confirmed that the net electrochemical H2 O2 generation rate on Pt/RSO was about twice lower than that on Pt/C. Kinetic parameters estimated for the ORR supported a direct 4e − pathway on both Pt/RSO (with ik of 4.5 mAcm −2, n = 3.97 and a Tafel slope of 64 mVdec −1 ) and Pt/ C (with ik of 4.1 mAcm −2, n = 3.93 and a Tafel slope of 68 mVdec −1 ). In conjunction with its high corrosion-resistance, this finding further illustrates the viability of RSO (and analogs such as ruthenium-titanium oxide) as outstanding PEFC electrocatalyst supports.