A Feasibility Study of Integrating CO2 Capture and Light‐Driven CO2 Conversion to a Fuel Junwang Tang,1* Zhengxiao Guo2 and Kimfung Li1 1. Chemical Engineering, UCL. Email: junwang.tang@ucl.ac.uk 2. Chemistry, UCL The upward spiral of CO2 concentration in the atmosphere triggered by
industrialization,
rising
commercial
and
domestic use of energy coupled with rapid rate
b
of deforestation could result in further increase
in the global average temperature followed by
methanol
rising sea levels and other dire consequences.
Photocatalytic conversion of CO2 to a more
stable energy carrier like methanol using
sunlight energy offers a sustainable solution to
address unnatural rise in CO2 level. However,
to be viable commercially, photocatalysts (or
photocatalyst systems) involved need to tap
more of the sunlight’s energy. This can only be
achieved if the photocatalysts/photocatalyst
systems involved are sensitive to the visible
wavelength range and have high energy
conversion efficiency.
CO
a
Fig. 1: (a) Baseline of sample before light
irradiation. (b) GC results show methanol and CO
production when the Ta-based photocatalyst is
exposed to light in one hour.
We have previously demonstrated facile synthesis of nanostructured films that are
sensitive to UV light irradiation via solution growth process. In this project, we tested
the UV sensitive nanostructured films, and found that they could actively reduce CO2
to fuel (CO and methanol), albeit under UV light irradiation (Fig 1). Currently, the
absolute amount of detected gaseous methanol is low. This is due to difficulties to
quantify reaction products that are soluble and unoptimized measurement and
reaction conditions that can be overcome with continuous efforts.
The next target within this project is to
tap into the most intense of the
sunlight radiation in the visible
wavelength range. We are convinced
that the way forward is to develop
visible light sensitive material by
selecting materials system with
suitable band energy, low enough for
visible light excitation, but straddling
CO2 reduction and water oxidation.
a b Fig. 2. Nanostructured visible light-driven Cu2O film.
(a) SEM observation and (b) pictures.
One of our approaches is by using copper based nanostructures. We focused on
copper based materials because of its appropriate bandgap in principal meeting the
requirement of CO2 reduction under visible light excitation. Cuprous oxides (CuO,
Cu2O) were investigated for water photolysis under visible light irradiation. However,
reports of CO2 reduction to fuel using copper based photocatalyst have been seldom
reported. Cu2O films have been successfully grown on glass substrate using simple
and reproducible solution growth method (Fig 2). The Cu2O films grown show
significant absorption well above 500nm wavelength, which makes it suitable to
capture the visible light radiation of the sun. It is underway to assess the activity of
the copper based films under visible light irradiations with and without bias. If
successful, it will be the first report on visible-driven CO2 photoreduciton and the
results will be filed.