Nanoalloy catalysts inside fuel cells: An atomic-level perspective on the functionality by combined in operando x-ray spectroscopy and total scattering

Fuel cells are a viable alternative to mankind's dependence on fossil fuels. Unfortunately, fuel cells are not on the market yet, mostly because of the lack of efficient and affordable catalysts for the sluggish chemical reactions driving cells' operation, such as the oxygen reduction reaction. Under operating conditions, the best catalysts developed so far would undergo specific atomic-level changes that inflict significant losses in their ORR activity, thereby limiting the cells' performance. Here we introduce an experimental approach for structural characterization of catalysts for fuel cells combining synchrotron x-ray spectroscopy and total scattering. The approach is demonstrated on exemplary Pd-Sn and Pt-Cu-Ni ORR catalysts functioning at the cathode of an operating proton exchange membrane fuel cell. We show that it allows probing catalysts inside operating fuel cells with atomic-level precision (~ 0.02 Å) and element specificity (~ 2-3 at%) in both time (~ 1 min) and space (~ µm) resolved manner. As such, the approach can help transform the promise of fuel cell technologies into an affordable reality.454