Electrocatalytic Reduction of Carbon Dioxide Using ... - David Boston

B8 Electrochemical and Solid-State Letters, 15 (1) B5-B8 (2012)
Figure 5. GC analyses as a function of time for constant-current electrolysis
of CO2-saturated solutions using: (a) Pt/C-TiO2 and (b) Pt foil cathodes.
Electrolysis conditions specified in the text.
Only methanol was seen as the CO2 electroreduction product in
the Pt foil case (Fig. 5b). Importantly, no CO was seen in the final
reduction products in either case in Figs. 5a and 5b. This is especially
significant in that metals such as Pt or Pd are known to selectively
produce CO on electroreduction of CO2; 4 clearly, the nanocomposite
matrix facilitates deeper reduction (to alcohols) beyond the 2e − CO
stage. The mechanistic factors underlying this trend will be further
probed in follow-on work that is planned.
Finally, we note that the production of alcohol per unit mass of Pt
for the nanocomposite matrix case (Fig. 5a)isthree orders of magnitude
larger than the Pt foil case (Fig. 5b). This represents substantial
reduction in Pt and is an important practical advance toward improving
the economics of electrochemical reduction of CO2 to liquid fuels.
Conclusions
This study has shown for the first time that nanocomposite cathode
matrices derived from either Pt/C-TiO2 or Pt-Pd/C-TiO2 are
effective electrocatalysts for aqueous CO2 reduction in the presence
of a solution co-catalyst such as the pyrdinium cation. In a
broader paradigm sense, the present findings (along with Ref. 7) also
serve to demonstrate that fuel cell cathode matrices may be good
candidates to drive multi-electron, multi-proton reduction reactions
such as CO2 reduction. It is worth noting in this regard that matrices
such as carbon black have good adsorption affinity for CO2 13
pointing to synergistic factors such as the site-proximity effect14 being
operative for nanocomposite matrices such as the ones developed
in this study. It is also recalled that Pt/C-TiO2 nanocomposite
cathodes have been previously deployed for oxygen reduction in a
1, 2, 15
proton electrolyte membrane fuel cell (PEM FC) environment.
Their application here, under nominally less corrosive conditions
(no reactive oxygen species), may offer a nanocomposite cathode
material of enhanced stability toward carbon corrosion and Pt
agglomeration.
Acknowledgments
The authors thank Drs. Wesley Wampler and Wen-Yuan Lin (Sid
Richardson Carbon & Energy Co) for donation of the carbon black
samples used in this study. This study was funded in part by a grant
from the U.S. Department of Energy. Finally, we thank an anonymous
reviewer for constructive comments on an initial manuscript version.
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