Biomedical Engineering Reference
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growth of the metal particles as well as deposition of a graphitic
coating on the metal particles, hindering access for gaseous molecules
such as hydrogen. Additionally, it is our experience that the presence
of cobalt during activation greatly accelerates carbon loss.
The goal of our research was to develop a new method that
would allow us to maintain the high surface area and microporosity
of pure CA, while also incorporating a uniform distribution of
metallic cobalt particles [52]. The CA was prepared by the method
mentioned in Section 3.2.1. A 0.1 M cobalt solution was prepared
from cobalt (II) acetate tetrahydrate (CH
O, reagent
grade, Sigma Aldrich) in deionized water for the coating process. The
solution of cobalt acetate was then added to the CA drop-wise and
the resultant cobalt slurry was centrifuged for 1 h to load the metal
ions into the pores of the CA. The cobalt content was predetermined
as 7.2 wt.% cobalt in CA. The sample was then pyrolyzed in a tube
furnace at 600°C for 1 h under a flowing nitrogen atmosphere (N
COO)
Co
⋅ 
4H
3
2
2
2
flow rate = 1.5 L/min). Following this pyrolysis, the sample was
reduced under a gas flow (10% H
and 90% Ar) at 500°C for 2 h.
The pure CA and the Co-doped CA will be referred to as CA and
CA-Co-I, respectively. For comparison, a further Co-doped sample
was also prepared by the ion exchange method [53], which is referred
to as CA-Co-II. The CA-Co-II sample was not activated under flowing
CO
2
, and was only carbonized at 900°C under a flowing nitrogen
atmosphere (N
2
flow rate = 1.5 L/min).
2
Figure 3.11
TEM micrograph of a typical cobalt-doped CA sample (CA-Co-I)
(scale bar in the figure is 100 nm) showing well dispersed
nanoscaled particles with the sizes between 2 and 8 nm
(black dots).
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