Reversibility in Structural Dynamics on Pt−Ni Bimetallic Nanocrystals under Redox Conditions

The reversibility of structural change in a bimetallic catalyst during the chemical reaction is an essential factor to determine the catalytic stability. Herein, we investigate the surface modulation of three Pt−Ni bimetallic alloy nanoparticle compositions (Pt₃Ni₁, Pt₁Ni₁, and Pt₁Ni₃) under alternating redox cycles. We validate trends in the structural change of the three compositions of Pt−Ni nanoparticles via spectroscopic/microscopic investigations at bulk and atomic levels. Pt-rich Pt−Ni nanoparticles exhibited higher reversibility in structural change during the repeated redox cycles. On the contrary, Ni-rich Pt−Ni nanoparticles showed irreversible structural changes, leading to the segregation and separation of Ni species from the alloy, which could deactivate the catalysts. This work demonstrates the reversibility of structural dynamics in alloy catalysts depending on their composition, providing fundamental insights for developing ideal bimetallic catalysts.