In the world of clean hydrogen, the smallest structures can cause the biggest problems. For Joshua Snyder, PhD, associate professor of chemical and biological engineering at Drexel, understanding why high-performing catalyst materials break down over time has become a defining scientific question and the inspiration for a new line of research that rethinks the very mechanics of degradation.
The issue centers on coarsening, the process by which catalytic materials gradually lose their nanoscale architecture. Traditionally, degradation of nanoparticulate electrocatalysts had been ascribed to Ostwald ripening, dissolution of small particles and growth of larger particles, leading to active material loss. But Snyder and his collaborators have shown that for three-dimensionally complex nanostructures, there are multiple mechanisms of mass mobility that lead to structural degradation. All of these mechanisms must be mitigated simultaneously to effectively improve electrocatalyst lifetime.
“What we found is that for complex nanostructures with three-dimensional morphology (porosity), structural collapse during operation is driven by both surface diffusion and dissolution/redeposition within the particle porosity,” Snyder said. In a real fuel cell, these collaborative mechanisms of atomic mobility for complex nano-morphologies fundamentally change how these materials evolve.”
The insight, described in two recent studies published in Nature Communications and the Journal of the American Chemical Society, highlights how electrochemical conditions accelerate degradation in unexpected ways. In acidic environments typical of fuel cells, high-curvature features created by porosity are particularly unstable. Curvature on an atomic-scale both creates surface atoms that are more susceptible to dissolution and establishes a chemical potential gradient that drive diffusion of atoms from areas of positive curvature to negative curvature, i.e. from a “hill” to a “valley.” These processes reduce the active surface area and with it, the catalyst’s effectiveness.
The problem is more than academic. Fuel cells and electrolyzers rely on rare, expensive metals like platinum and iridium to carry out key reactions. Nanoporous architectures offer a way to stretch these resources further by exposing more reactive surface per gram of metal. But when that structure fails, so does the efficiency that justified the material cost in the first place.
Snyder’s team explored this mechanism using nanoporous NiPt alloys, including variants doped with trace amounts of iridium or gold. They used computer models to mimic how atoms move and how the structure changes under real fuel cell conditions, then validated those predictions by putting the materials through accelerated stress tests. Spectroscopy and electron microscopy revealed the changes in detail. The results were clear: doped catalysts better maintained their surface area and structure.
“We’re talking about less than a quarter of a monolayer,” Snyder said. “But it makes a big difference. Those few atoms of iridium or gold help anchor the structure. They sit at the places where instability starts and slow everything down.”
The work reframes how researchers think about catalyst degradation. Maintaining the advantages imparted by complex, three-dimensional nano-morphologies requires addressing all mechanisms of atomic mobility that lead to structural evolution without adversely impacting catalyst activity.
This finding carries particular weight for the next generation of fuel cell and hydrogen generation technologies. These systems must operate at high power densities and endure thousands of operational hours to be commercially viable. Materials that cannot maintain their structure under those conditions will limit how far clean hydrogen can go.
“For acidic systems, we’re basically stuck with platinum, iridium and gold,” Snyder said. “Nothing else survives those conditions. So we have to make these materials last longer and work harder. Our work provides useful insight as to how we can do that.”
Snyder’s research aligns with his contributions to the Department of Energy’s Million Mile Fuel Cell Truck Consortium, which aims to deploy durable, high-performance fuel cells for long-haul trucking. His efforts are also supported by a Drexel Longsview Fellowship, which sponsors research enabling fundamental insights with practical implications.
“If we want to make hydrogen practical, we have to lower the cost,” Snyder said. “That means cheaper devices, more efficient reactions, and longer-lasting materials. We have to solve all three.”
By identifying the hidden drivers of catalyst breakdown and proposing precise atomic-scale interventions, Snyder is helping to transform how materials are designed for clean energy systems. His work moves the field closer to making hydrogen technologies not just effective, but sustainable in the long run.
