Angewandte Chemie International Edition
10.1002/anie.201712221
COMMUNICATION
intermediate. In this process, the reaction barrier may be also
+
reduced with the aid of the formation of [Bmim-CO
2
] , which
2
may
[
14]
·-
could reduce the overpotential. The protonation of CO
occur via capturing an electron-proton pair to form the adsorbed
-
-
HCO
2
(HCO2 ads). Because the carbon support surfaces have
[46]
low adsorption ability of CO
integral HCO2 ads is released to form formic acid.
In summary, the electrocatalytic reduction of CO
2
reduction intermediates,
the
-
2
to formic
acid was studied over MoP@In-PC, MoP@Ga-PC, MoP@PC-1,
MoP@PC-2, and bulk MoP using [Bmim]PF /MeCN/H O as the
2 6
Figure 4. A) Nyquist plots for five electrodes in CO -saturated [Bmim]PF (30
2-
6
2
wt%)/MeCN/H
2
O (5 wt%) electrolyte. B) Single oxidative LSV curves for SO
-saturated 0.1 M H SO
4
electrolyte. It was found that MoP@In-PC was very efficient and
stable electrocatalyst. The current density and Faradaic
adsorption over five electrodes in N
2
2
4
.
-2
efficiency of formic acid could be as high as 43.8 mA cm and
6.5 %, respecrtively. The detailed study indicated that the
9
EIS was conducted to investigate the properties of
electrode/electrolyte interface. The Nyquist plots can be
obtained by running the experiment at an open circuit potential
excellent catalytic performance of MoP@In-PC can be attributed
to the favorable character of nanoscale MoP, low interfacial
·-
charge transfer resistance, strong CO
2
and CO
2
intermediate
(
Figure 4A) and a simple equivalent circuit R(CR)W was then
adsorption ability, as well as the synergistic effect between MoP
and In-doped carbon supports. We believe that TMPs is very
used to fit the high and medium frequency data (Figure S35).
MoP@In-PC showed the lowest interfacial charge transfer
promising catalyst to replace expensive noble metals for CO
electroreduction to other useful chemicals or fuels.
2
resistance (Rct) due to stronger interaction and superior
cooperative effect between the nanosized MoP and In-PC. With
a higher overall electronic conductivity, electron transfer to
MoP@In-PC electrode surface in electrolyte is more facile than
to other electrode surface. It could ensure a faster electron
Acknowledgements
·-
transfer to CO
step of CO
2
for forming reduced CO
2
intermediate. As the
·-
The authors thank the National Key Research and Development
Program of China (2017YFA0403102), National Natural Science
Foundation of China (21533011, 21403253), and Chinese
Academy of Sciences (QYZDY-SSW-SLH013).
2
+ e → CO
2
is generally viewed as the rate-
determining step, the EIS results are in good agreement with the
trend of Tafel plots.
·
-
Additionally, the stabilization of reduced CO
2
intermediate
to
plays an important role in electrocatalytic conversion of CO
formic acid. In general, the overpotential of OH or SO
2
-
2-
Keywords: phosphides • carbon dioxide • electrocatalysis •
metal-organic frameworks • ionic liquids
4
adsorption is considered as a measure of binding strength of
[
11,12,40]
intermediates in the electrochemical reaction.
So we
2
-
·-
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examined SO
4
adsorption as a surrogate for CO
2
on the five
electrodes by measuring single oxidative LSV scans between 0
-1
and 1.7 V (vs. Hg/Hg
SO electrolyte, which could explore the binding affinity of the
reduced intermediate CO
reduction. The overpotential for surface SO
2 4 2
SO ) at 10 mV s in N -saturated 0.1 M
[
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2
4
-
[
MoP@In-PC was lower than the others as shown in Figure 4B.
Lower overpotential indicates larger binding energy and stronger
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2
-
·-
binding of SO
intermediates more efficiently.
semiconductor) was doped in the support, capturing quasi-free
electron by CO becomes much easier, resulting in stronger
4 2
, and hence MoP@In-PC could stabilize CO
[
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2
·-
[41]
CO
calculation also suggested that In is a high-overpotential metal
for H formation due to both local-geometric and local-electronic
2
adsorption on electrode surface.
The previous DFT
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[
[
[
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advantages in all the key steps for CO
formic acid.
On the basis of the results and the knowledge in the
literature, we proposed the possible pathway for the
2
electroreduction to
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2
to formic acid using MoP@In-PC
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2
+
[42-45]
adsorption via [Bmim-CO
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]
complex formation.
One
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·
-
electron was transferred to CO
2
molecule to form CO
2
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