An opinion on catalyst degradation mechanisms during catalyst support focused accelerated stress test (AST) for proton exchange membrane fuel cells (PEMFCs)

Abstract

Accelerated stress test (AST) protocol meant to study the durability of catalyst support in a polymer electrolyte membrane fuel cell (PEMFC) electrode has been critically evaluated. For nanoparticulate catalysts supported on high surface area conductive materials (e.g. Pt/C), potential cycling meant to study the support durability causes significant impact on the catalyst particles presumed to be passivated due to formation of oxide layer. X-ray diffraction (XRD) patterns of pre-AST and post-AST samples suggest significant change in crystallite size during potential cycling between 1.0 and 1.6 V (vs. RHE), which may be considered to growth induced by dissolution/redeposition rather than particle growth through agglomeration due to support corrosion. Significant (~50%) electrochemical surface area loss due to catalyst particle growth during support corrosion AST should be taken into account while development/screening of durable catalyst supports. To reduce such contribution, frequent observation cycle should be minimized.

Sustainable Platinum Recycling through Electrochemical Dissolution of Platinum Nanoparticles from Fuel Cell Electrodes

“…Hence, in absence of complexing agents, very little amount of Pt was removed from the WE due to the unstable nature of the Pt‐Oxides formed at potentials higher than ∼1 V at the low pH values of the studied electrolytes and high tendency for redeposition. However, the average Pt‐nanoparticle size increases during the electrochemical treatment due to Ostwald ripening . For example, the crystallite size of the electrode subjected to potential cycling (0.4–1.6 V; 100 mV/s) for 200 cycles in 1 M HNO 3 is observed to be 3.1 nm as compared to 2.0 nm of the pristine electrode (supporting information: S3).…”

“…4 have also been made in our previous studies. [31,[52][53] Hence, in absence of complexing agents, very little amount of Pt was removed from the WE due to the unstable nature of the Pt-Oxides formed at potentials higher than~1 V at the low pH values of the studied electrolytes [54] and high tendency for redeposition. However, the average Pt-nanoparticle size increases during the electrochemical treatment due to Ostwald ripening.…”

“…However, the average Pt-nanoparticle size increases during the electrochemical treatment due to Ostwald ripening. [31,53] For example, the crystallite size of the electrode subjected to potential cycling (0.4-1.6 V; 100 mV/s) for 200 cycles in 1 M HNO 3 is observed to be 3.1 nm as compared to 2.0 nm of the pristine electrode (supporting information: S3).…”

Synthesis of a Pt/C Electrocatalyst from a User-Friendly Pt Precursor (Ammonium Hexachloroplatinate) through Microwave-Assisted Polyol Synthesis

“…Thermogravimetric analysis (TGA) of typical Pt/C samples was performed using a NETZSCH STA449 F3 thermal analyzer (between 50 to 1000 o C at a temperature scan rate: [21][22] However, no such attempt has been made in the present study due to the fact that such high ECSA Pt/C might not be suitable for real-life PEMFC electrodes due to their lower stability. [36][37] Variations of the %ECSA values with N ( Fig. 3d) suggest both the H 2 PtCl 6 and the (NH 4 ) 2 PtCl 6sourced Pt/C catalysts to be equally durable.…”

Correlation between electrochemical performance degradation and catalyst structural parameters on polymer electrolyte membrane fuel cell

“…[16]. The DLC was characterized by the difference between cathodic and anodic currents on the active electrode area without any Faradaic reaction [17,18]. The variation of DLC during AST attributed to the carbon support corrosion.…”