Pt Nanoparticles on Atomic-Metal-Rich Carbon for Heavy-Duty Fuel Cell Catalysts: Durability Enhancement and Degradation Behavior in Membrane Electrode Assemblies

Abstract

Proton exchange membrane fuel cells (PEMFCs) are a promising zero-emission power source for heavy-duty vehicles (HDVs). However, long-term durability of up to 25,000 h is challenging because current carbon support, catalyst, membrane, and ionomer developed for traditional light-duty vehicles cannot meet the stringent requirement. Therefore, understanding catalyst degradation mechanisms under the HDV condition is crucial for rationally designing highly active and durable platinum group metal (PGM) catalysts for high-performance membrane electrode assemblies (MEAs). Herein, we report a PGM catalyst consisting of platinum nanoparticles with a high content (40 wt %) on atomic-metal-site (e.g., MnN4)-rich carbon support. MEAs with the Pt (40 wt %)/Mn–N–C cathode catalyst achieved significantly enhanced performance and durability, generating 1.41 A cm–2 at 0.7 V under HDV conditions (0.25 mgPt cm–2 and 250 kPaabs pressure) and retaining 1.20 A cm–2 after an extended and accelerated stress test up to 150,000 voltage cycles. Electron microscopy studies indicate that most fine Pt nanoparticles are retained on or/and in the carbon support covered with the ionomer throughout the catalyst layer at the end of life. During the long-term stability test, the observed electrochemical active surface area reduction and performance loss primarily result from Pt depletion in the catalyst layer due to Pt dissolution and redeposition at the interface of the cathode and membrane. The first-principle density functional theory calculations further reveal a support entrapment effect of the Mn–N–C, in which the MnN4 site can specifically adsorb the Pt atom and further retard the Pt dissolution and migration, therefore enhancing long-term MEA durability.

Unraveling a volcanic relationship of Co/N/C@PtxCo catalysts toward oxygen electro-reduction

“…Recently, coupled PGM-free@PGM catalysts have been reported, which involve both M/N/C and PtM alloy nanoparticles. 26–36 Attractively, as far as we know, the highest reported ORR activity (2.48 A mg Pt −1 @0.9 V 37 ) and stability (97% activity retention after 100 000 cycles 32 ) in PEMFC membrane electrode assemblies are based on this coupled catalyst.…”

Spontaneous Demetallation of Mn(II)Nx Catalytic Sites in Proton Exchange Membrane Fuel Cell Conditions

“…It seems that the latter catalysts are still of interest as supports for Pt nanoparticles, which would be held more firmly in place on Mn/N/C than on an N-doped carbon support devoid of Mn sites. These particular interactions would increase the stability of platinum catalysts. − …”

Designing and Engineering Atomically Dispersed Metal Catalysts for CO2 to CO Conversion: From Single to Dual Metal Sites

“…Notably, such atomic metal sites in carbon support could yield a synergistic coupling effect with loaded metal nanoparticles (Pt, Pd, Au, Sn, or Cu) due to the possible electron exchange. [124][125]140] This could provide new pathways to design and synthesize tandem catalysts for CO 2 conversion to C 2 and C 3 products. [22,141] In addition to innovative catalyst design, flow reactor engineering plays a crucial role in translating the highperformance catalyst into efficient CO production at industry-level current densities.…”