supporting information self-supported ni(oh)2/mno2 on cfp ......s-1 supporting information...

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Supporting Information

Self-supported Ni(OH)2/MnO2 on CFP as a Flexible Anode

towards Electrocatalytic Urea Conversion: the Role of

Composition on Activity, Redox States and Reaction

Dynamics

Jianfang Menga, Petko Chernev

b, Mohammad Reza Mohammadi

b, Katharina Klingan

b, Stefan

Loosb,d

, Chiara Pasquinib, Paul Kubella

b, Shan Jiang

b, Xianjin Yang

a,c, Zhenduo Cui

a, Shengli

Zhua,c

, Zhaoyang Lia,c

, Yanqin Lianga,c

,Holger Daub

aSchool of Materials Science and Engineering, Tianjin University, Tianjin 300072, China

bDepartment of Physics, Free University of Berlin, Arnimallee 14, 14195, Berlin, Germany

cTianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072, China

dFraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM)

Winterbergstraße 28, 01277 Dresden, Germany

*Corresponding author. E-mail: yqliang@tju.edu.cn (Y. Q. Liang), holger.dau@fu-berlin.de

(H. Dau)

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Fig. S1 SEM images of (a) CFP-NiMn1.4 and (b) CFP-NiMn4.0.

Fig.S2 XRD patterns of MnO2 powder and CFP-NiMn2.4.

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Fig.S3 (a) XPS spectrum of CFP-NiMn2.4. High resolution spectra of (b) O 1s, (c) Ni

2p, (d) Mn 2p, and (e) XPS spectrum of CFP-Mn2 and high resolution spectra of (f)

Mn 2p, the inset in (d) is the enlarged spectra of Mn 2p2/3 of CFP-NiMn2.4 (black) and

CFP-Mn2 (red).

X-ray photoelectron spectra detect signals from Mn, Ni, C and O elements. The

elemental manganese and nickel are generated from MnO2 and the Ni(OH)2,

respectively. The two signals at 642.4 eV for Mn 2p3/2 and 653.9 eV for Mn 2p1/2

observed in CFP-Mn2, are characteristic of MnO2. Moreover, the small shift of Mn

2p3/2 peak to lower binding energy (642.2 eV) is observed after Ni deposition, most

possibly caused by the electrochemical reduction of Mn species, which is accordance

with XAS result. But due to the susceptibility of Mn-oxide materials, we cannot rule

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out the possibility of other forms of charging path inducing to the tiny shift in binding

energy.1-2

The Ni(OH)2 state is confirmed by principal peaks at 855.5 eV in high-

resolution Ni 2p XPS spectrum. The spectra of O 1s further confirm the existence of

MnO2 (530.0 eV) and Ni(OH)2 (531.2 eV).

Fig. S4 Cyclic voltammogram of CFP-Mn1, CFP-Mn2, and CFP-Mn3 recorded in 1 M

KOH (a) and 1 M KOH&0.5 M urea (b).

Fig. S5 Tafel slopes obtained from quasi stationary measurements for OER in 1 M

KOH (a) and UOR in 1 M KOH&0.5 M urea (b)

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Fig.S6 Nyquist plots of different catalysts for OER process at 1.70 V vs. RHE (a) and

for UOR process at 1.45 V vs. RHE (b).

Fig. S7 UOR stability performance for CFP-NiMn2.4. Galvanostation (V-t)

measurement performed at a constant current density of 10 mA cm-2

in 1M KOH and

0.5 M urea electrolyte over 10000 s.

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Fig. S8 SEM image of CFP-NiMN2.4 catalyst after UOR glavanostation tests.

Fig. S9 Concentration of metals obtained from TXRF analysis before and after CV

electrochemical measurement.

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Fig. S10 Relation between catalytic TOF value and one electron oxidation equivalent

(nred/(nNi+nMn) in percent) for CFP-Ni(OH)2, CFP-NiMn1.4, CFP-NiMn2.4, and CFP-

NiMn4.0 after operation in KOH (a) and KOH&urea (b). Catalyst loadings (nNi+nMn)

were determined by TXRF analysis after measurements. Turnover frequency (TOF)

of CFP-NiMn catalysts based on the total metal loading of Ni+Mn extracted from

steady state current densities in KOH at 1.65 V vs. RHE, and in KOH&urea at 1.51 V

vs. RHE (only based on Ni metal loading molar quantity).

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Fig. S11 (a) The schematic diagram of direct urea/O2 fuel cell configuration, (b) the

open circuit voltage of the cell tested by the multimeter.

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Fig. S12 Extended X-ray absorption fine structure (EXAFS), (a) Mn K-edge of as-

prepared catalysts before and after conditioning in KOH and KOH&urea, (b) Ni K-

edge of as-prepared catalysts before and after conditioning in KOH and KOH&urea.

Catalysts were frozen under applied potential after conditioning at 1.627 V vs RHE

for 2 min.

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Table S1. Parameters obtained by simulation of the k3-weighted EXAFS spectra for

Mn. The simulated spectra correspond to the Fourier-transformed EXAFS spectra

shown in Figure 3f, in which σ values for Mn-Mn shells are fixed. The errors

represent the 68% confidence interval of the respective fit parameter (N, coordination

number; R, absorber-backscatter distance; σ, Debye-Waller parameter; an amplitude-

reduction factor, S02=0.7)

N R [Å] σ [Å]

Mn2 Mn-O 5.6± 0.3 1.888±0.004 0.054±0.001

Mn-Mn, di-μ-

oxo

5.0± 0.3 2.868±0.004 0.059

Mn2-oper in

KOH

Mn-O 5.8± 0.3 1.897±0.004 0.059±0.001

Mn-Mn, di-μ-

oxo

5.8± 0.3 2.888±0.004 0.059

Mn2-oper in

KOH&urea

Mn-O 5.7± 0.3 1.892±0.004 0.051±0.001

Mn-Mn, di-μ-

oxo

5.6± 0.3 2.885±0.004 0.059

NiMn2.4 Mn-O 5.2± 0.3 1.896±0.004 0.051±0.001

Mn-Mn, di-μ-

oxo

5.0± 0.3 2.878±0.004 0.059

NiMn2.4-

oper in

KOH

Mn-O 5.8± 0.3 1.903±0.003 0.056±0.001

Mn-Mn, di-μ-

oxo

6.0± 0.3 2.892±0.002 0.059

NiMn2.4-

oper in

KOH&urea

Mn-O 5.8± 0.3 1.900±0.004 0.060±0.001

Mn-Mn, di-μ-

oxo

5.9± 0.3 2.898±0.004 0.059

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References

(1) Kochur A. G., Kozakov A. T., Googlev K. A., Nikolskii A. V., Journal of Electron

Spectroscopy and Related Phenomena 2014, 195, 1-7.

(2) Ilton E. S., Post J. E., Heaney P. J., Ling F. T., Kerisit S. N., Applied Surface Science 2016,

366, 475-485.