Energy crisis and environmental pollution are two of the most
serious issues the world faces. It is urgent for us to produce
green renewable energy to solve these problems. Since Honda
and Fujishima discovered phenomena of photoelectronchemical
water splitting [1], H2 production from water using
solar energy [2e5] is regarded as one of the most promising
ways to obtain renewable hydrogen energy [6e10]. Development
of supported catalyst is the key issue and main challenge
for practical application of this technique.
CdS is one of the most popular photocatalysts for its high
activity on visible-light-driven water decomposition, and
have been studied over 30 years. The band-gap (2.4 eV) of CdS
is well coincident with the spectrum of sunlight in visible
light with a more negative conduction band than the H2O/H2
redox potential [11e13]. Many researchers, including our
group are focusing on further improving its activity [14e21].
One of the approaches is to combine CdS with supporting
materials to accelerate the charge separation and migration
in the photocatalytic procedure. On the other hand, for carbon
nanotubes (CNTs), they are allotropes of carbon with a
cylindrical nanostructure with diameter lower than 100 nm
and have novel properties that make them potentially useful
in many applications in nanotechnology [22e24]. Consequently,
the migration of photogenerated charges inside CdS
would be accelerated due to the excellent electroconductibility
of CNTs, which shall improve the photocatalytic
activity. So CNTs were used as such supporting
materials in our study. Similar work has been reported before
[25], but the photoactivity of CdS/CNTs photocatalyst they
offered is not outstanding.