A Model Study for Oxygen Reduction Reaction and Durability of Pt/C Catalyst in Triple-Phase Boundary of PEFCs

Abstract

We developed a novel solid-state electrochemical cell for modeling triple-phase boundary of polymer electrolyte fuel cells and investigated oxygen reduction reaction (ORR) activity and durability of Pt/C catalysts using the cell. ORR current was depended on relative humidity as well as the thickness of coated Nafion layer on the model electrode. We also conducted the theoretical calculation and clarified that ORR current in the model TPB region is not restricted by oxygen diffusion but by an ohmic drop due to proton migration in the coated Nafion layer on the model electrode.Durability test of Pt/C catalysts in the model TPB region was carried out under oxygen atmosphere. After the test, aggregation and somewhat larger Pt particles were observed on the model electrode at which electrode potential would reach to be open circuit potential, i.e., low overpotential region, under oxygen atmosphere.

In situ S-K XANES study of polymer electrolyte fuel cells: changes in the chemical states of sulfonic groups depending on humidity

“…26 The mechanism of degradation of PEFCs due to aggregation of platinum particles by sweeping potential or long-term operation was two-dimensionally or three-dimensionally analyzed using various microscopy and spectrometry techniques. [27][28][29][30][31] Nafion is known as a relatively stable polymer but in the fuel cell particularly during power generation it was found to be decomposed by the generated hydrogen peroxide. [31][32][33][34][35] It should be noted that X-ray and g-ray induced radiation damage of Nafion has been also reported.…”

“…[31][32][33][34][35] It should be noted that X-ray and g-ray induced radiation damage of Nafion has been also reported. [36][37][38][39][40][41] In order to follow the response by external stimuli as well as the degradation, in situ observations of model cells similar to practical equipment [5][6][7][15][16][17][18][19]21,22,28,[33][34][35] are essentially important.…”

Carbon black functionalized by grafting of Azo‐generated‐radicals as electrocatalyst support for the oxygen reduction reaction

“…In theory, the surface of Pt NPs homogeneously dispersed on carbon support forms a triple phase boundary with reactant/product gases and with the ionomer, which in practice is a delicate balance of interdependent trade-offs. [5] For instance, too little ionomer near the Pt NPs leads to detrimental increase in ionic resistance, but raising the amount of ionomer instead leads to new detrimental effects such as (i) the poisoning of the Pt electroactive surface by the ionomer or (ii) the increase in local O 2 mass transport resistance. [6,7] The local O 2 mass transport resistance is particularly detrimental to the performances of PEMFCs with low cathodic Pt loading (below 0.1 mg Pt /cm geo 2 ) and operating at relatively high current density.…”

Theoretical Calculations of Organic Salts and Their Correlation with Proton Conductivity

“…The design and synthesis of the proton conduction of the organic salt are crucial for the enhanced proton conductivity of the fuel cell component. 30,31 Herein, we describe the experimental synthesis/electrochemical properties of polymer-based organic salts. Subsequently, we investigated the influence of the type of acid modification on the organic salt model in the polymer side chain using density functional theory (DFT) simulations.…”