Towards a highly-efficient fuel-cell catalyst: optimization of Pt particle size, supports and surface-oxygen group concentration

2013 ◽  
Vol 15 (11) ◽  
pp. 3803 ◽  
Author(s):  
Navaneethan Muthuswamy ◽  
Jose Luis Gomez de la Fuente ◽  
Piotr Ochal ◽  
Rajiv Giri ◽  
Steinar Raaen ◽  
...  
Keyword(s):  
Particle Size ◽  
Fuel Cell ◽  
Surface Oxygen ◽  
Fuel Cell Catalyst ◽  
Highly Efficient ◽  
Surface Oxygen Group ◽  
Oxygen Group ◽  
Group Concentration

Tracking the Catalyst Layer Depth-Dependent Electrochemical Degradation of a Bimodal Pt/C Fuel Cell Catalyst: A Combined Operando Small- and Wide-Angle X-Ray Scattering Study

2021 ◽  
Author(s):  
Johanna Schröder ◽  
Rebecca K. Pittkowski ◽  
Isaac Martens ◽  
Raphaël Chattot ◽  
Jakub Drnec ◽  
...  
Keyword(s):  
Particle Size ◽  
Fuel Cell ◽  
Ostwald Ripening ◽  
Catalyst Layer ◽  
Wide Angle ◽  
Layer Depth ◽  
X Ray ◽  
Fuel Cell Catalyst ◽  
X Ray Scattering ◽  
Size Population

The combination of operando small- and wide-angle X-ray scattering (SAXS, WAXS) is here presented to provide insights into the changes in mean particle sizes and phase fractions in fuel cell catalyst layers during accelerated stress tests (ASTs). As fuel cell catalyst, a bimodal Pt/C catalyst was chosen that consists of two distinguishable particle size populations. The presence of the two different sizes should favor and uncover electrochemical Ostwald ripening as degradation mechanism, i.e., the growth of larger particles in the Pt/C catalyst at the expense of the smaller particles via the formation of ionic metal species. However, instead of electrochemical Ostwald ripening, the results point toward classical Ostwald ripening via the local diffusion of metal atoms on the support. Furthermore, the grazing incidence mode provides insights into the catalyst layer depth-dependent degradation. While the larger particles show the same particle size changes close to the electrolyte-catalyst interface and within the catalyst layer, the smaller Pt nanoparticles exhibit a slightly decreased size at the electrolyte-catalyst interface. During the AST, both size populations increase in size, independent of the depth. Their phase fraction, i.e., the ratio of smaller to larger size population, however, exhibits a depth-dependent behavior. While at the electrolyte-catalyst interface the phase fraction of the smaller size population decreases, it increases in the inner catalyst layer. The results of a depth-dependent degradation suggest that employing a depth-dependent catalyst design can be used for future improvement of catalyst stability.

scholarly journals Theoretical analysis of particle size re-distribution due to Ostwald ripening in the fuel cell catalyst layer

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 779-789 ◽  
Author(s):  
Ambrož Kregar ◽  
Tomaž Katrašnik
Keyword(s):  
Particle Size ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Electric Potential ◽  
Ostwald Ripening ◽  
Particle Growth ◽  
Mean Particle Size ◽  
Fuel Cell Catalyst

Abstract The limited durability of hydrogen fuel cells is one of the main obstacles in their wider adoption as a clean alternative technology for small scale electricity production. The Ostwald ripening of catalyst material is recognized as one of the main unavoidable degradation processes deteriorating the fuel cell performance and shortening its lifetime. The paper systematically studies how the modeling approach towards the electrochemically driven Ostwald ripening in the fuel cell catalyst differs from the classical diffusion driven models and highlights how these differences affect the resulting evolution of particle size distribution. At moderately low electric potential, root-law growth of mean particle size is observed with linear relation between mean particle size and standard deviation of particle size distribution, similar to Lifshitz-Slyozov-Wagner theory, but with broader and less skewed distribution. In case of high electric potential, rapid particle growth regime is observed and qualitatively described by redeposition of platinum from a highly oversaturated solution, revealing the deficiencies of the existing platinum degradation models at describing the Ostwald ripening in the fuel cells at high electric potentials. Several improvements to the established models of platinum degradation in fuel cell catalysts are proposed, aimed at better description of the diffusion processes involved in particle growth due to Ostwald ripening.

Tracking the Catalyst Layer Depth-Dependent Electrochemical Degradation of a Bimodal Pt/C Fuel Cell Catalyst: A Combined Operando Small- and Wide-Angle X-Ray Scattering Study

2021 ◽  
Author(s):  
Johanna Schröder ◽  
Rebecca K. Pittkowski ◽  
Isaac Martens ◽  
Raphaël Chattot ◽  
Jakub Drnec ◽  
...  
Keyword(s):  
Particle Size ◽  
Fuel Cell ◽  
Ostwald Ripening ◽  
Catalyst Layer ◽  
Wide Angle ◽  
Layer Depth ◽  
X Ray ◽  
Fuel Cell Catalyst ◽  
X Ray Scattering ◽  
Size Population

The combination of operando small- and wide-angle X-ray scattering (SAXS, WAXS) is here presented to provide insights into the changes in mean particle sizes and phase fractions in fuel cell catalyst layers during accelerated stress tests (ASTs). As fuel cell catalyst, a bimodal Pt/C catalyst was chosen that consists of two distinguishable particle size populations. The presence of the two different sizes should favor and uncover electrochemical Ostwald ripening as degradation mechanism, i.e., the growth of larger particles in the Pt/C catalyst at the expense of the smaller particles via the formation of ionic metal species. However, instead of electrochemical Ostwald ripening, the results point toward classical Ostwald ripening via the local diffusion of metal atoms on the support. Furthermore, the grazing incidence mode provides insights into the catalyst layer depth-dependent degradation. While the larger particles show the same particle size changes close to the electrolyte-catalyst interface and within the catalyst layer, the smaller Pt nanoparticles exhibit a slightly decreased size at the electrolyte-catalyst interface. During the AST, both size populations increase in size, independent of the depth. Their phase fraction, i.e., the ratio of smaller to larger size population, however, exhibits a depth-dependent behavior. While at the electrolyte-catalyst interface the phase fraction of the smaller size population decreases, it increases in the inner catalyst layer. The results of a depth-dependent degradation suggest that employing a depth-dependent catalyst design can be used for future improvement of catalyst stability.

scholarly journals Tracking the Catalyst Layer Depth-Dependent Electrochemical Degradation of a Bimodal Pt/C Fuel Cell Catalyst: A Combined Operando Small- and Wide-Angle X-Ray Scattering Study

2021 ◽  
Author(s):  
Johanna Schröder ◽  
Rebecca K. Pittkowski ◽  
Isaac Martens ◽  
Raphaël Chattot ◽  
Jakub Drnec ◽  
...  
Keyword(s):  
Particle Size ◽  
Fuel Cell ◽  
Catalyst Layer ◽  
Grazing Incidence ◽  
Phase Fraction ◽  
Wide Angle ◽  
X Ray ◽  
Fuel Cell Catalyst ◽  
X Ray Scattering ◽  
Ray Scattering

The combination of operando small- and wide-angle X-ray scattering (SAXS, WAXS) in grazing incidence configuration is presented as a new approach to provide depth-dependent insights into the changes in mean particle sizes and phase fractions occurring for fuel cell catalysts during accelerated stress tests (ASTs). As fuel cell catalyst, a bimodal Pt/C catalyst was chosen that consists of two distinguishable particle size populations. The presence of the two different sizes should favor and uncover electrochemical Ostwald ripening as the major degradation mechanism, i.e., it is expected that the size of the larger particles in the Pt/C catalyst grows at the expense of the smaller particles. The grazing incidence mode performed at the European Synchrotron Radiation Facility (ESRF) at the ID31 beamline revealed an intertwinement of the depth dependent degradation. While the larger particles show the same particle size changes close to the electrolyte-catalyst interface and within the catalyst layer, for the smaller Pt nanoparticles a different degradation scenario is observed. At the electrolyte-catalyst interface, the smaller particles increase in size while their phase fraction decreases during the AST. However, in the inner catalyst layer the phase fraction of smaller particles increases instead of decreases. The results of a depth-dependent degradation strongly suggest to employ a depth-dependent catalyst design for future improvement of the catalyst stability.

Decoupling the effect of Ni particle size and surface oxygen deficiencies in CO2 methanation over ceria supported Ni

2021 ◽  
Vol 286 ◽  
pp. 119922
Author(s):  
Ziwen Hao ◽  
Jindong Shen ◽  
Shuangxi Lin ◽  
Xiaoyu Han ◽  
Xiao Chang ◽  
...  
Keyword(s):  
Particle Size ◽  
Surface Oxygen ◽  
Co2 Methanation ◽  
Supported Ni
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