  Introduction of interstitial dopants has opened a new pathway to optimize
nanoparticle catalytic activity for, e.g., hydrogen evolution/oxidation and
other reactions. Here, we discuss the stability of a property-enhancing dopant,
B, introduced through controlled synthesis of an electrocatalyst Pd aerogel. We
observe significant removal of B after the hydrogen evolution/oxidation
reaction. Ab-initio calculations show that the high stability of sub-surface B
in Pd is substantially reduced when H is ad/absorbed on the surface, favoring
its departure from the host nanostructure. The destabilization of sub-surface B
is more pronounced as more H occupies surface sites and empty interstitial
sites. We hence demonstrate that the H2 fuel/product itself favors the
microstructural degradation of the electrocatalyst and an associated drop in
activity.

Materials Science