Fig. 2: H2 etching process of a PtOx layer. | Nature Materials

Fig. 2: H2 etching process of a PtOx layer.

From: Two-dimensional crystalline platinum oxide

Fig. 2

a, Evolution of the O1s spectra of PtOx under 1 mbar H2 at 1,000 K; the spectra were collected under a photon energy of 1,486.6 eV. b, In situ SEM images recorded the etching behaviour of PtOx on a Pt(9 10 7) surface showing anisotropic evolution under 1 mbar H2 at 1,000 K (Supplementary Video 3). Note: the sequence of images shows the appearance of new edges at the concave corner during the coalescence of etching pits (highlighted by red arrows). c, Shape evolution of the etching pits during H2 etching, reproduced as the colour-coded superposition of outlines abstracted from images recorded at 53 s intervals. d, Orientation of the Pt substrate is determined by EBSD and presented in the Pt unit cell. The coloured arrows indicate the <111> directions for the unit cell. e, The corresponding ball model. f, Ball model of the unreconstructed (9 10 7) surface orientation of the underlying Pt grain. The yellow line highlights the surface step, with the uphill direction indicated by the red labelled arrow. g, Representative details of the vacancy islands (etching pits) in b. The shape of the vacancy islands almost perfectly overlaps the triangle surrounded by the stripes along [1 0 −1], [0 1 −1] and the line along the (9 10 7) surface step. h, Colour-coded shape evolution of an etching pit according to the growth time provided in the colour legend. The black dotted line indicates the missing half of the regular triangle shape. i, Schematic of the attachment of one of the vacancy island edges to the Pt step site. j, Shape evolution of the etching pits represented in polar coordinates shows anisotropic growth behaviour. Note: the initiation site of the etching pits is from the pole of the polar coordinates. k, Simulated kinetic Wulff construction of growth.

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