Activity, Stability, and Degradation Mechanisms of Dealloyed PtCu₃ and PtCo₃ Nanoparticle Fuel Cell Catalysts

Abstract

A key challenge in today’s fuel cell research is the understanding and maintaining the durability of the structure and performance of initially highly active Pt fuel cell electrocatalysts, such as dealloyed Pt or Pt monolayer catalysts. Here, we present a comparative long‐term stability and activity study of supported dealloyed PtCu3 and PtCo3 nanoparticle fuel cell catalysts for the oxygen reduction reaction (ORR) and benchmark them to a commercial Pt catalyst. PtCu3 and PtCo3 were subjected to two distinctly different voltage cycling tests: the “lifetime” regime [10 000 cycles, 0.5–1.0 V vs. RHE (reversible hydrogen electrode), 50 mV s−1] and the corrosive “start‐up” regime (2000 cycles, 0.5–1.5 V vs. RHE, 50 mV s−1). Our results highlight significant activity and stability benefits of dealloyed PtCu3 and PtCo3 for the ORR compared with those of pure Pt. In particular, after testing in the “lifetime” regime, the Pt‐surface‐area‐based activity of the Pt alloy catalysts is still two times higher than that of pure Pt. From our electrochemical, morphological, and compositional results, we provide a general picture of the temporal sequence of dominant degradation mechanisms of a Pt alloy catalyst during its life cycle.

Nitrogen-doped coatings on carbon nanotubes and their stabilizing effect on Pt nanoparticles

“…The growth rate was found to be dependent on the surface area of the carbon support with high surface area carbons showing a slower Pt coarsening rate than low surface area supports. 5,6 In parallel to the particle coarsening, carbon supports corrode and degrade due to the high cathodic electrode potentials. Much has been learned about the molecularscale degradation mechanisms of fuel cell cathodes, 8 however, to date, robust and practical material-design strategies to mitigate the structural degradation of carbon-supported Pt nanoparticle catalysts has remained scarce.…”

“…The ECSA loss is a macroscopic descriptor for the total catalytically active surface area and is affected by a large number of different factors, such as particle dispersion, support structure, and the accessibility of particles on the support surface. With initial ECSA values in the 50-60 m 2 g À1 range, 5,6 both catalysts showed similar ECSA losses over the 2400 potential cycles of 33% for the uncoated CNT and somewhat reduced 27% for the N-CNT supported particles.…”

Elemental Anisotropic Growth and Atomic-Scale Structure of Shape-Controlled Octahedral Pt–Ni–Co Alloy Nanocatalysts

“…By alloying Pt with other non-noble metals, it is possible to produce cheaper electrocatalysts with novel properties for the oxygen reduction reaction (ORR) due to lattice compression 5,6 and/or modified electronic properties 7,8 . Thus, several studies have shown that binary Pt-M (M=Cr, Mn, Fe, Co, Ni, Cu, V, Ti) nanocrystals (NCs) greatly enhanced the kinetics of the ORR in comparison with standard Pt catalysts [9][10][11] . However, besides the composition, the intrinsic activity of nanoparticles also depends on their size and shape which strongly determine the atomic surface structure of the nanoparticles [12][13][14][15] .…”

Gold-promoted structurally ordered intermetallic palladium cobalt nanoparticles for the oxygen reduction reaction

“…Key strategies to reduce Pt contents involve alloying Pt with other transition metal [3][4][5][6][7][8] , de-alloying non-precious metal to obtain a Pt rich shell [9][10][11] and core-shell-structured nanoparticles [12][13][14][15] . These approaches, to some degree, increase Pt utilization, but cannot fully solve the problem of Pt dependence.…”