Making Pt-shell Pt₃₀Ni₇₀ nanowires by mild dealloying and heat treatments with little Ni loss

Dealloying treatment is one way to make a Pt rich shell on Pt alloy through chemically depleting the surface of non-noble metals. However, this treatment usually causes more than half of the non-noble metal to be lost before the catalyst forms an effective protective surface. This process may cause unfavorable morphology and size change of the alloy catalyst. Our research indicates that a mild dealloying treatment in acid combined with an annealing treatment could make an effective Pt rich surface layer when only a little non-noble metal is dissolved from the alloy surface. Pt-Ni alloy nanowires are chosen as the treatment target because long nanowires are mechanically more stable than nanoparticles, which tend to migrate, agglomerate and lose surface area during working. Pt-Ni nanowires are made by electrospinning followed by a mild dealloying treatment and a post-heat treatment to make a core-shell structure in which Ni loses only ∼10 atom% and the resultant Pt-shell could prevent nickel (>70 atom% of the whole wire) in the core from dissolving in 1 M hot sulfuric acid. These long nanowires have diameters around 10-20 nm and form a self-supporting net.