Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Metal oxide nanomaterials for pseudocapacitors   With the rapid development of economy, the consumption of fossil fuels, and
the increasing environment pollution, there is in urgent need of seeking clean
and renewable energy sources, as well as highly efficient and low-cost energy
storage technologies. Concerning electrochemically active materials, transition
metal oxides (TMOs) are regarded as the most promising candidates for the next
generation SCs and have been widely reported. Therefore, in this review, we
mainly pay attention to TMOs with excellent electrochemical performance. This
review is divided into four parts: (a) the background including energy storage
mechanisms and electrochemical characterizations of SCs; (b) various kinds of
TMOs for SCs are analyzed in detail involved in crystal structure,
conductivity, and energy storage mechanism; (c) hybridizations with other
materials to improve the electrochemical performance of TMOs are summarized and
discussed; (d) a perspective and short remarks about the development and design
of TMOs for superior performance SCs are shown.

17
The categories of this paper are: q-fin
25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs