(AR, Sinopharm Chemical Reagent Co. Ltd), potassium bicarbonate
(KHCO3, ≥99.99%, Sigma-Aldrich), Nafion solution (5 wt%, Sigma-Aldrich),
and carbon dioxide (CO2, 99.995%, Specialty Gases Co. Ltd) were
used as received. Deionized water (18.2 MΩ, Milli-Q water purification
system) was used to prepare electrolyte solutions. SnO2 nanoparticle
(99.99%, 50–70 nm, Macklin) and carbon paper (Hesen Co. Ltd,
HPCP030) were used in control experiments.
dimethylsulfoxide as internal standard in D2O for NMR analysis. The
same acquisition parameters were chosen for all NMR spectra, notably a
minimum of 64 scans for a clearer distinction between signal and noise.
Supporting Information
Catalysts Synthesis and Electrode Preparation: The WIT SnO2 nanofiber
was fabricated by electrospinning. Briefly, 1.5 g SnCl2·2H2O and 1.0 g
PVP were dissolved in 10 mL mixed solvents (DMF with ethanol, 1:1 by
volume) with magnetic stirring for 12 h at room temperature. Obtained
solution was used as the precursor for electrospinning. Carbon paper
was used to collect the pristine nanofibers. The voltage was set at 15 kV,
the distance between the carbon paper and the needle was 15 cm, and
the precursor flow rate was 40 µL min−1. The obtained electrospun
nanofibers were then oxidized at 500 °C for 2 h at atmosphere. The NP
SnO2 was commercially available and used as received.
The catalysts loaded electrodes were prepared using a drop-casting
deposition method. Carbon paper was used as the electrode substrate
after cleaning with acetone and deionized water. WIT SnO2 nanofibers
and NP SnO2 inks for drop-casting deposition were prepared by mixing
carbon black (CB, 10 mg), WIT SnO2 nanofibers or NP SnO2 (10 mg),
Nafion solution (0.5 wt%, 100 µL), and alcohol (1 mL). The mixture
was then sonicated for 60 min after high speed stirring overnight and
drop-casted (≈100 µL) onto the carbon paper (1 × 1 cm2). The catalyst
loading was ≈1 mg cm−2. Then, the electrodes were dried at 60 °C for
2 h. Carbon black was chosen as the support and dispersing agent due
to its high conductivity and stability.[46]
Supporting Information is available from the Wiley Online Library or
from the author.
Acknowledgements
L.F. and Z.X. contributed equally to this work. The authors acknowledge
the financial support from the National Key R&D Program of China
(2016YFA0202900), the Natural Science Foundation of China (Grant
Nos. 21436007, 21576235, U1462201, and 21676242) and the Zhejiang
Provincial Natural Science Foundation (Grant No. LY16B060005). L.F.
thanks Prof. Qiaohong He, Prof. Xiaokun Ding, and Prof. Fang Chen
of the Department of Chemistry, Zhejiang University for TEM and
SEM analyses. Z.X. thanks Jianyang Pan (Pharmaceutical Informatics
Institute, Zhejiang University) for performing NMR spectrometry for
structure elucidation.
Conflict of Interest
Material Characterization: The morphology of the WIT SnO2 nanofibers
and NP SnO2 was observed by SEM (SU-8010, Hitachi) and TEM
(200 KV-2100F, JEOL). XRD (Shimadzu) was used to determine
the crystalline structure of the WIT SnO2 nanofibers and NP SnO2.
Automatic surface area and porosity analyzer (Micromeritics) was
employed to record the nitrogen adsorption–desorption isotherms. The
specific surface area and pore size distributions were estimated by BET
and Barrett–Joyner–Halenda methods, respectively. Surface elemental
analysis of the WIT SnO2 nanofiber before and after electrochemical
reaction was conducted on Escalab 250Xi (Thermo Fisher Scientific) XPS
with an Mg Kα X-ray resource.
The authors declare no conflict of interest.
Keywords
C1 products, CO2 reduction, grain boundaries, 1D SnO2, wire-in-tube
structures
Received: October 30, 2017
Revised: January 20, 2018
Published online:
Electrochemical CO2 Reduction Activity Evaluation: Electrochemical CO2
reduction was performed in a gastight two-compartment electrochemical
cell separated by a Nafion 117 membrane with a three-electrode setup
(schematic diagram shown as Figure S1, Supporting Information).
A Biologic VP-300 electrochemical workstation was used to precisely
control the working electrode potential in chronoamperometry mode
using a Pt mesh counter electrode and an Ag/AgCl reference electrode
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E RHE =E Ag/AgCl + 0.210 V + 0.0591V ×pH
(1)
(
)
(
)
All potentials present in this paper were versus RHE, unless stated
otherwise. The electrolyte solution in both compartments was 0.1
m
KHCO3 (pH = 6.8, after purging CO2 for 1 h). CO2 was continuously
purged into the cathodic compartment (20 mL min−1) through a gas
diffuser during the constant potential electrolysis. All electrocatalytic
tests were carried out at a constant temperature of 25 °C.
CO2 Reduction Products Quantification:
A gas chromatograph
(GC, 9790, Fuli Co. Ltd) with a thermal conductivity detector and a flame
ionization detector was used to quantify the concentration of gaseous
products including H2 and CO. Products concentration measured by the
GC were averaged across aliquots. H2 and CO production rate and FE
were determined based on their concentrations as reported previously.[47]
Liquid products of the electrochemical reduction of CO2 were quantified
using 1D 1HNMR. 1H spectra were recorded on Bruker Avance DRX
400 (500 MHz). The water peak was suppressed by a modified WET
solvent suppression technique. 600 µL of the electrolyte after electrolysis
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containing CO2 reduction products was mixed with 70 µL of 10 × 10−3
m
©
Adv. Funct. Mater. 2018, 1706289
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