Temperature Dependence of Oxygen Reduction Activity at Nafion-Coated Bulk Pt and Pt/Carbon Black Catalysts

Abstract

Oxygen reduction reaction (ORR) activity and H(2)O(2) formation at Nafion-coated film electrodes of bulk-Pt and Pt nanoparticles dispersed on carbon black (Pt/CB) were investigated in 0.1 M HClO(4) solution at 30 to 110 degrees C by using a channel flow double electrode method. We have found that the apparent rate constants k(app) (per real Pt active surface area) for the ORR at bulk-Pt (with and without Nafion-coating) and Nafion-coated Pt/CB (19.3 and 46.7 wt % Pt, d(Pt) = 2.6 to 2.7 nm) thin-film electrodes were in beautiful agreement with each other in the operation conditions of polymer electrolyte fuel cells (PEFCs), i.e., 30-110 degrees C and ca. 0.7 to 0.8 V vs RHE. The H(2)O(2) yield was 0.6-1.0% at 0.7-0.8 V on all Nafion-coated Pt/CB and bulk-Pt and irrespective of Pt-loading level and temperature. Nafion coating was pointed out to be a major factor for the H(2)O(2) formation on Pt catalysts modifying the surface property, because H(2)O(2) production was not detected at the bulk-Pt electrode without Nafion coating.

Oxygen electroreduction on carbon-supported Pd nanocubes in acid solutions

“…It has been also suggested that Nafion coating increases the peroxide yield on Pt catalysts [38]. Recently similar behaviour was observed on Pd catalysts, which also showed decreasing diffusion limiting current plateau with increasing Nafion content [39].…”

Oxygen Reduction Reaction Activity of Carbon-Supported Pt-Fe, Pt-Co, and Pt-Ni Alloys with Stabilized Pt-Skin Layers

“…11 The working electrode was Nafion μ -coated Pt 2AL -Pt-M/C uniformly dispersed on an Au substrate (geometric area 0.04 cm 2 ), which was prepared in the similar manner as that described in our previous work. 11,18 The amount of each catalyst was maintained at a constant loading of carbon support at 15 µg carbon cm ¹2 (corresponding to an approximately three-layer height of carbon particles 18 ), and the average thickness of Nafion μ was 0.1 µm. The ORR activities of the commercial Pt catalyst supported on carbon black (TEC10E50E, 50 wt%-Pt, specific surface area of the carbon support = ca.…”

“…monolayer height), because the dispersion state of this catalyst on the Au substrate was found to be more uniform, thus providing the intrinsic activity as described later. 11,18 The reference electrode used was a reversible hydrogen electrode (RHE), and all of the potentials will be referred to the RHE in this paper.…”

Research and Development of Highly Active and Durable Electrocatalysts Based on Multilateral Analyses of Fuel Cell Reactions

“…Moreover, Pt/CB was uniformly dispersed on a gold substrate electrode at a constant loading of CB support, 5.5 µg cm ¹2 (corresponding to approximately one monolayer of CB particles) and coated with a thin Nafion film (0.1 µm), in order to minimize the O 2 diffusion resistance within the thin catalyst layer. 39 We have demonstrated that the ORR rate constant (k app , per unit ECA), its activation energy, and P(H 2 O 2 ) in O 2 -saturated 0.1 M HClO 4 were all independent of d Pt from Pt 1.6nm /CB to bulk-Pt at 30 to 50°C, as well as from Pt 2.6nm /CB to bulk-Pt up to 110°C. 40 It was also found that the smallest (Pt 1.6nm ) particles agglomerated at higher temperatures (² 60°C).…”

“…[1][2][3][4] For PEFC anode and cathode catalysts, the activity and its degradation have been analyzed by multilateral techniques such as X-ray photoelectron spectroscopy combined with an electrochemical cell (EC-XPS), 2,[5][6][7][8] in situ Fourier-transform infrared spectroscopy (FTIR), [9][10][11][12][13][14][15][16][17][18][19][20][21][22] electrochemical quartz crystal microbalance (EQCM), [23][24][25][26] in situ scanning tunneling microscopy (STM), [27][28][29][30][31] in addition to conventional electrochemical measurements such as rotating disk electrode (RDE), [32][33][34] channel flow electrode (CFE), 21,35,36 and channel flow double electrode (CFDE) methods. [37][38][39][40][41][42] Based on these results, new practical catalysts have been synthesized. [43][44]…”