  Dissolution of electrocatalysts during long-term and dynamic operation is a
challenging problem in energy conversion and storage devices such as fuel cells
and electrolyzers. To develop stable electrocatalysts, we adopt the design
concept of segregation engineering, which uses solute segregation prone to
electrochemical dissolution at internal defects, i.e., grain boundaries and
dislocations. We showcase the feasibility of this approach by stabilizing a
model Pt catalyst with an addition of more noble Au (approximately 5 atomic
percent). We characterized the defects' nanoscale structure and chemistry, and
monitored the electrochemical dissolution of Pt and PtAu alloys by online
inductively coupled plasma mass spectrometry. Once segregated to defects, Au
atoms can stabilize and hence passivate the most vulnerable sites against
electrochemical dissolution and improve the stability and longevity of the Pt
electrocatalysts by more than an order of magnitude. This opens pathways to use
solute segregation to defects for the development of more stable nanoscale
electrocatalysts, a concept applicable for a wide range of catalytic systems.
