Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Metal-insulator transition of the reduced surface of yttria-stabilized
  zirconia near Pt electrodes   The electrochemical reactions of solid oxide fuel cells occur in the region
where gas-phase species, electrode, and electrolyte coincide. When the
electrode is an ionic insulator and the electrolyte is an electronic insulator,
this `triple phase boundary' is assumed to have atomic dimensions. Here we use
photoemission electron microscopy to show that the reduced surface of the
electrolyte yttria-stabilized zirconia (YSZ) undergoes a metal-insulator
transition near Pt negative electrodes. YSZ's electron conducting region
functions as an extended triple phase boundary that can be many microns in
size, depending on oxygen pressure, temperature, applied voltage, and time.

32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas