Supporting Information

FeCo Alloy Nanoparticles Confined in Carbon Layers as

High-activity and Robust Cathode Catalyst for Zn-Air

BatteryPingwei Cai,1,2 Suqin Ci,1* Erhuan Zhang,1 Ping Shao,1 Changsheng Cao,2 and

Zhenhai Wen1,2*1 Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources Recycle, Nanchang Hangkong University, Nanchang 330063, China2 Fujian Provincial Key Laboratory of Nanomaterials, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China

E-mail: sqci@nchu.edu.cn, sllou@hnu.cn or wen@fjirsm.ac.cn

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Table of Contents:

Part I: Characterization of the samples;

Part II: Electrochemical testing results;

Part III: References.

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Part I: Characterization of the samples

Fig. S1 SEM images of Co-Fe PBA at different scale.

Fig. S2 XRD pattern of Co-Fe PBA.

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Fig. S3 TEM images of as-synthesized FeCo@NC-750 at different scale.

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Fig. S4 (a) Atomic percent of elements, (b) High resolution spectrum of N1s before and after argon sputtering, (c-d) XPS spectra of Fe 2p and Co 2p core level respectively.

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Part II: Electrochemical testing results;

Fig. S5 (a) Chronoamperometric response at a constant potential of 1.505 V, (b) polarizations before and after stability test of FeCo@NC-750.

Fig. S6 CVs of FeCo@NC-550, (b) FeCo@NC-650 at different scan rate from 2 to 10 mV s-1.

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Fig. S7 XRD pattern of Co@NC-750 (a) and Co-Co PBA (b).

Fig. S8 (a) polarization, (b) Tafel plot, (c) CVs at different scan rate from 2 to 10 mV s-1, (d) Plots of the current density at 1.32 V vs. the scan rate of Co@NC-750.

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Fig. S9 (a) polarizations, (b) Tafel plots of FeCo@NC-750, FeCo-750 and NC-750 respectively. (c, d) CVs at different scan rate from 2 to 10 mV s -1 and (inset) plot of the current density at 1.32 V vs. the scan rate of FeCo-750 and NC-750.

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Fig. S10 (a-c) Polarization curves at the rotating speed from 400 to 2500 rpm,(d-f) responding K-L plots of 20% Pt/C, FeCo@NC-550 and FeCo@NC-650 respectively.

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Fig. S11 (a, b) Polarization curves before and after stability, (c, d) amperometric i-t curve of FeCo@NC-750 and 20% Pt/C

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Supplementary TablesTable S1. Comparison of the OER activity for several recently reported highly active metal and metal-free catalysts.

CatalystPotential@

10.0mA cm-2

(V vs. RHE)Tafel slope(mV dec-1)

Electrolyte Reference

nNiFe LDH/NGF ~1.54 45 0.1 M KOH S1

N-graphene /CNT 1.65 N.A. 0.1 M KOH S2

Co3O4/N-PC 1.62 72 0.1 M KOH S3

(Co0.54Fe0.46)2P 1.60 N.A. 0.1 M KOH S4

NiOOH/Ni5P4 1.52 40 1.0 M KOH S5

Co3O4C-NA 1.52 70 1.0 M KOH S6

CoOOH Nanosheets

1.53 38 1.0 M KOH S7

NG-CNT 1.61 75-80 0.1 M KOH S8

Co3O4/NiCo2O4

Nanocages1.57 88 1.0 M KOH S9

NixCo3-xO4 ~1.56 60 1.0 M NaOH S10

Co nanoparticles 1.62 N.A. 0.1 M KOH S11

NiFe@NC 1.51 70 1.0 M NaOH S12

S,S’-CNT 1.58 95 1.0 M KOH S13

NCNT/CoxMn1-xO 1.57 40 1.0 M KOH S14

FeCo@NC-550 1.68 119 1.0 M KOH This workFeCo@NC-650 1.55 85 1.0 M KOH This workFeCo@NC-750 1.49 52 1.0 M KOH This work

Table S2. The values of the equivalent circuit elements on the analysis

of FeCo@NC.

Catalyst Rs (ohm) Rint(ohm) Rct (ohm)

FeCo@NC-550 35.6 35.2 288.5

FeCo@NC-650 31.4 10.8 103.2

FeCo@NC-750 13.7 8.97 91.7

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Table S3 Comparison of the ORR activity for several recently reported

highly active metal and metal-free catalysts.

Catalyst Half-wave potential

Electron-transfer number

Tafel slope(mV dec-1)

Reference

P-CNCo-20 0.84 3.9 N/A S15

CNT/Fe3C N/A 3.99 91.2 S16

Fe3C/C-800 0.83 3.8-4.0 N/A S17

N-Co9S8/G N/A 3.7-3.9 N/A S18

Co@Co3O4@C-CM

0.81 V 3.8-3.9 N/A S19

Co/NG N/A 3.8 N/A S20

Co-C@Co9S8

DSNCsN/A 3.8 N/A S21

Carbon-L 0.70 V 3.68 N/A S22

Z8-Te-1000 0.80 ~4.0 N/A S23

GNPCSs-800 N/A 3.78-3.98 N/A S24

Co, N-CNF 0.81 3.8 60 S25

FeCo@NC-750 0.80 ~3.9 54.6 This work

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