Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Ni-Fe Layered Double Hydroxide-Carbon Nanotube Complex for Water
  Oxidation   Highly active, durable and cost-effective electrocatalysts for water
oxidation to evolve oxygen gas hold a key to a range of renewable energy
solutions including water splitting and rechargeable metal-air batteries. Here,
we report the synthesis of ultrathin nickel iron layered double hydroxide
nanoplates on mildly oxidized multi-walled carbon nanotubes. Incorporation of
Fe into the nickel hydroxide induced the formation of NiFe-layered double
hydroxide. The nanoplates were covalently attached to a network of nanotubes,
affording excellent electrical wiring to the nanoplates. The ultra-thin Ni-Fe
layered double hydroxide nanoplates/carbon nanotube complex was found to
exhibit unusually high electro-catalytic activity and stability for oxygen
evolution and outperformed commercial precious metal Ir catalysts.

35
The categories of this paper are: mtrl-th
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org