Selected examples for additional microstructural
signatures. (A)
Cyclic voltammogram of current I versus electrode
potential E for NPG in deaerated 0.1 mol L–1 NaOH. Dark blue: scan to the switching potential at the Burshtein
minimum (indicated by label). The shaded area under the surface oxide
reduction peak scales with the surface area and can be used to measure
that quantity. Light blue: scan to larger positive switching potential;
note the larger reduction charge. (B) Grain size of NPG from electron
backscatter diffraction in a scanning electron microscope.115 Color codes crystallographic orientation, identifying
individual crystal grains as regions of uniform color. Note up to
100 μm grain size, more than thousandfold larger than the ligament
size, LSEM = 18 nm here. (C) Solid fraction,
φ, of NPG versus initial Au fraction, xAu0, in the starting
alloy.118 Strong deviation at low xAu shows that the starting alloy composition does not provide a good
indicator of NPG solid fraction. Note also the dependency on the preparation
protocol, free versus electrochemical corrosion. (B) Reproduced with
permission from ref (115). Copyright 2021 from Elsevier. (C) Reproduced with permission from
ref (118). Copyright
2021 The Authors.