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Supporting Information

A Sustainable Synthesis of Nickel-Nitrogen-Carbon Catalysts for Efficient

Electrochemical CO2 Reduction to CO

John Pellessier, Yang Gang, and Ying Li,*

J. Mike Walker '66 Department of Mechanical Engineering, Texas A&M University, College Station, Texas, 77843, United States

* Corresponding Author E-mail: yingli@tamu.edu

Table of Contents

Faradaic Efficiency Calculation

Figure S1-S9

Table S1-S4

S1

Faradaic Efficiency Calculation: Faradaic efficiency (FE) of gaseous products at each applied

potential was calculated based on the equation:

FE=z ∙ P ∙ F ∙ V ∙ v i

R ∙ T ∙ J

Where z was the number of electrons transferred per mole of gas product (2 for CO and H2), P

was the pressure in the cell which was atmospheric for these test (1.01 × 105 Pa), F is the Faraday

constant (96500 C mol−1), V was the gas volumetric flow rate of pure CO2 (68 × 10−6 m3/s), vi

was the volume concentration of gas product determined by GC, R is the gas constant (8.314

J/[mol·K]), T was the temperature in the cell which was standard for these test (298.15 K), and J

is the steady-state current measured at each applied potential (A).

Fig. S1 Sample structure of unit from cornstarch.

S2

Fig. S2 Cyclic voltammograms curves performed at various scan rates (10, 20, 40, 60, 80 and 100 mV·s−1) on (A) CS-N-Ni-500, (B) GO-500, and (C) CS-N-Ni-WI.

S3

20 40 60 80 100Scan rate (mV/s)

0.5

1

1.5

2

2.5

3

3.5 J

(mA

/cm

2 )CS-N-Ni-500GO-N-Ni-500CS-N-Ni-WI

Cdl=14.3mF/cm2

Cdl=29.2mF/cm2

dCdl=13.8mF/cm2

Fig. S3 The double-layer capacitance Cdl (the slope) of different experimental groups.

0 200 400 600 800 1000

Binding Energy (eV)

Inte

nsity

(a.u

.)

CS

0 200 400 600 800 1000

Binding Energy (eV)

Inte

nsity

(a.u

.)

CS-N

0 200 400 600 800 1000

Binding Energy (eV)

Inte

nsity

(a.u

.)

CS-N-Ni-500

A B

C

Fig. S4 XPS spectra of CS, CS-N, and CS-N-Ni-500.

S4

Fig. S5. 1H NMR spectra of cathode side electrolyte after 2h electrolysis at - 0.8 V vs RHE over CS-N-Ni-

500.

-1.1-1-0.9-0.8-0.7-0.6-0.5-0.4

V vs RHE

0

20

40

60

80

100

FEH

2(%)

CSCS-NCS-N-Ni-10CS-N-Ni-100CS-N-Ni-500CS-N-Ni-1000

Fig. S6. Faradaic efficiency of H2 production of CS, CS-N, and CS-N-Ni-X catalysts (X = 10 – 1000).

S5

Fig. S7. 24-hour stability test of CS-N-Ni-500 run under a constant potential of -0.8 V versus

RHE.

S6

-1.1-1-0.9-0.8-0.7-0.6-0.5-0.4

V vs RHE

-20

-15

-10

-5

0C

urre

nt D

ensi

ty (m

A/c

m2 )

CS-N-Ni-500CS-N-Ni-500-AW

-1.1-1-0.9-0.8-0.7-0.6-0.5-0.4

V vs RHE

0

20

40

60

80

100

FEC

O(%

)

CS-N-Ni-500CS-N-Ni-500-AW

-1.1-1-0.9-0.8-0.7-0.6-0.5-0.4

V vs RHE

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

J CO

(mA

/cm

2 )

CS-N-Ni-500CS-N-Ni-500-AW

A B

C

Fig. S8. (A) Total current density, (B) Faradaic efficiency of CO production, and (C) CO current

density of CS-N-Ni-500 and CS-N-Ni-500-AW.

S7

-1.1-1-0.9-0.8-0.7-0.6-0.5-0.4

V vs RHE

0

20

40

60

80

100FE

H2(%

)

CS-N-Ni-500GO-N-Ni-500CS-N-Ni-WI

Fig. S9. Faradaic efficiency of H2 production of CS-N-Ni-500, GO-N-Ni-500, and CS-N-Ni-WI.

Table S1 EIS fitting results for different experimental groups.

Catalyst Rs(Ω) RΩ(Ω) RCT(Ω)

CS-N 1.8 1.7 257

CS-N-Ni-500 1.4 2.7 21.2

GO-500 1.7 2 20.7

CS-N-Ni-WI 1.7 1.7 15

S8

Table S2 Metal concentrations detected by ICP-MS.

Concentration (wt%)

MetalPre-Pyrolysis CS-N-Ni-500

CS-N-Ni-500Pre-Pyrolysis GO-N-Ni-500

GO-N-Ni-500

Nickel 0.1 0.26 1.3 2.8

Table S3 CH4, H2, and CO concentrations measured by GC and total current measured by electrochemical station CS-N, CS-N-Ni-500, CS-N-Ni-WI, and GO-N-Ni-500.

Potential

(V vs.

RHE)

CS-N CS-N-Ni-500 CS-N-Ni-WI GO-N-Ni-500

CH4

(ppm)

H2

(ppm)

CO

(ppm)

Current

(mA)

CH4

(ppm)

H2

(ppm)

CO

(ppm)

Current

(mA)

CH4

(ppm)

H2

(ppm)

CO

(ppm)

Current

(mA)

CH4

(ppm)

H2

(ppm)

CO

(ppm)

Current

(mA)

-0.5 0 1 2 -0.045 0 6 18 -0.25 0 7 13 -0.25 0 36 58 -0.93

-0.6 0 5 6 -0.13 0 9 162 -1.75 0 13 130 -1.4 0 55 348 -3.85

-0.7 0 18 18 -0.4 0 18 633 -6.5 0 25 531 -5.3 0 91 849 -9

-0.8 0 64 59 -1.3 0 36 1305 -12.6 0 55 1045 -10 0 191 1258 -14.2

-0.9 0.18 159 87 -2.45 0.12 86 1445 -15 0.5 209 1216 -13.1 0.19 464 1368 -17.4

-1.0 0.67 604 92 -6.8 0.67 285 1657 -18 2 716 1170 -18.2 0.72 1186 1295 -22.5

S9

Table S4 Comparison of electrochemical CO2RR performances for CO production between the

catalysts in this work and reported C-N-Ni catalysts.

Catalysts Conc. of KHCO3

(M)

FE COa

(%)

JCOb

(mA/cm2)Potential

(V vs. RHE)

Carbon Precursor Pre- or Post- Treatment

References

CS-N-Ni-500

0.5 92 11.64 -0.77 Cornstarch N/A This work

CS-N-Ni-1000

0.5 93 13.31 -0.76 Cornstarch N/A This work

Ni-N-PC 0.5 97 18 -0.8 Petroleum Coke Acid/ethanol wash

[1]

CB-NGC-2 0.1 91 ~4.5 -0.56 Wood Biomass Acid/ethanol wash

[2]

NiSA-NCNT 0.5 87 13 -0.6 C2H8N2 No [3]

Ni-N-RGO 0.5 97 19 -0.8 NTB Acid/ethanol wash

[4]

Ni-NG 0.5 95 12.5 -0.8 Graphene Oxide Nanosheets

Freeze drying [5]

Ni-N-C 0.1 ~80 12 -0.85 Ketjen600EC Acid/ethanol wash

[6]

Ni-NCB 0.5 97 14 -0.8 Carbon Black Acid/ethanol wash

[7]

Ni SAs/N-C 0.5 71.9 10.48 -1.0 ZIF-8 No [8]

Ni-N-C 0.1 85 <10 -0.78 4,4′-Dipyridyl hydrate

Acid/ethanol wash

[9]

Ni-N-C 0.1 97 7.51 -0.75 Methylimidazole Acid/ethanol wash

[10]

Ni-N-Gr 0.1 80 0.2 -0.65 Graphite Oxides Acid/ethanol wash

[11]

Ni/N-C 0.5 97.5 9 -0.61 p-Phthalaldehyde Acid/ethanol wash

[12]

Ni-N4-C 0.5 99 28.6 -0.81 Dicyandiamide Freeze drying [13]

Ni-N-C 0.5 93 6 -0.8 o-phenylenediamine Acid/ethanol wash

[14]

Ni3N/MCN T-1

0.5 89 1.5 -0.73 Multiwalled CNT Acid/ethanol wash

[15]

Ni3N/MCN T-1

0.5 70 6 -0.83 Multiwalled CNT Acid/ethanol wash

[15]

Ni@NCNTs 0.5 99.1 8.01 -0.8 Dicyandiamide Acid/ethanol wash

[16]

a The maximum FE for CO productionb CO partial current density at the potential where the maximum FE is obtained

S10

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