Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Doping of Self-Standing CNT Fibers: Promising Flexible Air-Cathodes for
  High Energy Density Structural Zn-air batteries   Finding proper electrocatalysts capable of efficient catalyzing both ORR and
OER is of great importance for metal-air batteries. With increasing inclination
towards structural and flexible devices, developing a high-performance
self-standing air-cathode is highly demanded and challenging, as most of oxygen
catalysts are powder and need to be further processed. Here, we construct
highly bifunctional air catalyst from macroscopic CNT fibers (CNTf) through
direct CVD spinning followed by hydrothermal method. The electrocatalytic
properties of the samples were tuned by altering nitrogen-doping and defect
densities readily adjusted at different hydrothermal reaction temperatures. The
treated CNTfs showed excellent bifunctional activity ({\Delta}E=Ej=10-E1/2=0.81
V) and demonstrated exceptional performance as carbon-based self-standing
air-cathodes in liquid and solid-state rechargeable Zn-air batteries, with high
capacity of 698 mAh g-1 and ultrahigh energy density of 838 Wh kg-1. The
rechargeable Zn-air batteries exhibit a low discharge-charge overpotential and
excellent stability. This work provides novel simply achieved self-standing air
electrodes with exceptional performance for structural Zn-air batteries.

22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex
13
The categories of this paper are: quant-ph
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org