What is it about?
In a Polymer Electrolyte Membrane Fuel Cell (PEMFC), platinum (Pt) is the essential catalyst that enables the conversion of hydrogen into electricity. However, platinum is not as "noble" as once thought; under certain electrical and thermal conditions, it can dissolve. This study investigates the aggressive role of temperature in accelerating this decay. The researchers developed a specific Accelerated Stress Testing (AST) protocol: a "potentiostatic square-wave" that forced the cell to jump between 0.6 V and 1.0 V every three seconds. This electrical cycling was performed at three distinct temperatures: 40°C, 60°C, and 80°C. Using a suite of advanced diagnostics, the team observed: Platinum Migration: Scanning Electron Microscope (SEM) images revealed that dissolved platinum doesn't just vanish; it travels into the proton-exchange membrane, forming a "Pt band" that serves no catalytic purpose. Surface Area Collapse: The Electrochemical Active Surface Area (ECSA) dropped sharply as temperatures rose, directly correlating to a spike in polarization resistance. Kinetic Mapping: The team created a diagnostic expression that uses the "Effective Platinum Surface Area" (EPSA) to calculate exactly how much voltage is lost due to the slowing of the oxygen reduction reaction.
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Why is it important?
To make hydrogen vehicles competitive, they need to operate at higher temperatures (80°C+) to reject heat more efficiently and improve reaction speeds. However, this study proves there is a heavy "durability tax" for doing so. This research is critical for: Thermal Management Design: It quantifies the trade-off between performance and longevity, helping engineers decide the "sweet spot" for fuel cell operating temperatures. Predictive Diagnostics: The new diagnostic expression allows researchers to estimate kinetic losses without destroying the cell, making it easier to monitor the health of a fuel cell during its operation. Material Development: By confirming exactly where the platinum goes (the "Pt band" in the membrane), the study provides a target for material scientists to develop "migration-resistant" membranes or more stable catalyst supports.
Perspectives
This study highlights the "thermal fragility" of modern electrocatalysts. While platinum is incredibly efficient, its tendency to dissolve and migrate at 80°C represents a fundamental bottleneck for heavy-duty hydrogen applications, such as long-haul trucking or shipping, where engines must run hot and hard for thousands of hours. The most insightful aspect of this work is the development of the EPSA-based kinetic loss expression. It bridges the gap between microscopic material loss and macroscopic power drops. It tells us that we aren't just losing "mass"; we are losing the "active frontier" where chemistry becomes electricity. As the industry pushes toward "High-Temperature PEM" technology, the findings here serve as a cautionary tale: temperature is a double-edged sword. To build a 20,000-hour fuel cell, we must solve the "Pt migration" problem highlighted by these SEM images. This work provides the mathematical and visual evidence needed to move from observing degradation to actively preventing it through better thermal control and stabilized catalyst structures.
Dr. Shankar Raman Dhanushkodi
University of British Columbia
Read the Original
This page is a summary of: Study of the effect of temperature on Pt dissolution in polymer electrolyte membrane fuel cells via accelerated stress tests, Journal of Power Sources, January 2014, Elsevier,
DOI: 10.1016/j.jpowsour.2013.07.016.
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