Synthesis of Mesoporous LiMn 2 O 4 and LiMn 2-x Co x O 4 Thin Films Using MASA Approach as Efficient Water Oxidation Electrocatalysts.

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1 Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A. This journal is The Royal Society of Chemistry 218 Synthesis of Mesoporous LiMn 2 and LiMn 2-x Co x Thin Films Using MASA Approach as Efficient Water Oxidation Electrocatalysts. Fadime Mert Balci, 1 Irmak Karakaya, 1 Elif Pınar Alsaç, 1 Muammer Yusuf Yaman, 1 Gülbahar Saat, 1 Ferdi Karadas,* 1,2 Burak Ülgüt, 1 and Ömer Dag* 1,2 1 Department of Chemistry, Bilkent University, 68, Ankara, Turkey. 2 UNAM National Nanotechnology Research Center and Institute of Materials Science and Nanotechnology, Bilkent University, 68, Ankara, Turkey. Figure S1. Small angle XRD patterns of fresh samples of 6 salt/p123 and various CTAB/P123 ratios, (I), (II) 1, (III) 3, and (IV) 5. 1

2 2 (111) Intensity/cps o C 55 o C 5 o C 45 o C 4 o C 35 o C (222) (311) (4) 3 o C / o (331) 65 o C * * Figure S2. XRD patterns of meso-limn 2, calcined at 3-65 o C, bottom to top (indexed using PDF card of JCPDS ). (511) (44) (531) (622) 2

3 35 Intensity/cps (111) (311) (222) (4) (331) (511) (44) (531) (622) / o Figure S3. XRD pattern of meso-limn 2, prepared using 3, 6, and 9 salt/p123 mole ratios, bottom to top, respectively. 3

4 (a) 2 Quantity Adsorbed/cm 3 /g, STP (b) 15 (98 m 2 /g) (68 m 2 /g) 5 3 (6 m 2 /g) Relative Pressure/P/Po dv/dw o Pore Size/A Figure S4. N 2 (77.4K) sorption isotherms (a) and BJH pore size distribution plots (b) of meso-limn 2, prepared using 3, 6, and 9 salt/p123 mole ratios. 4

5 16 Intensity/a.u LiMn 2 LiMn 1.5 Co.5 LiMnCo LiMn.5 Co 1.5 LiCo Wavenumber/cm -1 Figure S5. Raman spectra of meso-limn 1-x Co x. 5

6 6

7 Figure S6. TEM images of meso-limnco at various magnifications. 7

8 Mn Mn Co Co LiMn 2 LiMn 1.5 Co.5 Counts LiMnCo LiMn o.5 Co 1.5 LiCo Figure S7. EDX spectra of meso-limn 2-x Co x. Energy/keV 8

9 Equation y = a + b*x Adj. R-Square Value Standard Error %75co (co) Intercept %75co (co) Slope E-4 Equation y = a + b*x Adj. R-Square Value Standard Error %5co (co) Intercept %5co (co) Slope E-4 Equation y = a + b*x Adj. R-Square Value Standard Error %1Co Intercept %1Co Slope E-4 (a) Equation y = a + b* Adj. R-Squar Value Standard Erro %25Co (co) Intercept E-4 %25Co (co) Slope E Scan Rate/mV/s 2 mv/s 2 mv/s (b) Scan rate/mv/s 2 mv/s 2 mv/s Potential/V vs NHE (c) mv/s Scan rate/mv/s 2 mv/s Potential/V vs NHE (d) Scan rate/mv/s 2 mv/s 2 mv/s Potential/V vs NHE Potential/V vs NHE Figure S8. CVs of LiMn 2-x Co x with different scan rate (2-2 mv/s), x is (a) 1.5, (b) 1., (c).5 and (d).. Inset shows linearity of current density of Co 2+/3+ oxidation peak versus scan rate. 9

10 .45 Overpotential/V %1Mn %75Mn %25Co %5Mn %5Co %25Mn %75Co %1Co Linear Fit of %1Mn Linear Fit of %75Mn %25Co Linear Fit of %5Mn %5Co Linear Fit of %25Mn %75Co Linear Fit of %1Co Logj/log A/cm 2 %1Mn y=.124x+.789 R 2 =,998 %75Mn y=,66x+,51 R 2 :,998 %5Mn y=,64x+,473 R 2 :,996 %25Mn y=,66x+,482 R 2 :,995 %1Co y=,64x+,472 R 2 :,999 Figure S9. Tafel plots obtained for LiMn 2-x Co x modified electrodes at ph

11 .6 Overpotential/V %Mn %1Co %25Mn %75Co %5Mn %5Co %75Mn %25Co %1Mn %Co Time/s Figure S1. Chronopotentiometric experiments performed on electrodes at ph 13.6 at a current density of 1 ma cm -2 for three hours. 11

12 (a) 2 15 After %Mn%1Co Before %Mn%1Co (b) 2 15 After %25Mn%75Co Before %25Mn%75Co Potential/V vs NHE Potential/V vs RHE (c) 2 15 After %5Mn %5Co Before %5Mn%5Co (d) 2 15 After %75Mn%25Co Before %75Mn%25Co (e) Potential/V vs NHE) After %1Mn%Co Before %1Mn%Co Potential/V vs NHE Potential/V vs NHE Figure S11. CVs performed on electrodes before (red curves) and after (blue curves) chronopotentiometric experiment displayed in Figure S8. 12

13 LogTOF/log(s -1 ) %1Mn %75Mn %5Mn %25Mn %Mn Overpotential/V Figure S12. Dependence of turnover frequencies of LiMn 2-x Co x modified electrodes recorded at ph =

14 4 3 LiMn 2 LiMn 1.5 Co.5 LiMnCo LiMn.5 Co 1.5 LiCo E vs. Ag/AgCl Figure S13. The IR compensated CV data for different compositions showing water oxidation. 14

15 Table S1. A summary of electrochemical properties of lithium metalates and some of the most studied mixed metal oxides. Compounds ph Tafel Slope η 1mA η 1mA Mass activity Reference (mv dec -1 ) (mv) (mv) At 4 mv, (A g -1 ) LiCoO [1] De-LiCoO [1] De-LiCo.33 Ni.33 Mn.33 O [1] LT-LiCoO [2] LiCO 2 nanosheets [3] De-LiCO 2 nanosheets [3] LiCO 2 nanoparticles [3] De-LiCO 2 nanoparticles [3] LiMn 2 -carbon composite 13 1 (at ~5 mv) [4] LiMn [5] LiMn 1.5 Co [5] LiMnCo [5] LiMn.5 Co [5] LiCoO [5] LiNi.9 Co.1 O 2 14 ~25 a Li 1.3 Ni.66 Co.21 Fe.1 O 1.95 ~1 a LiMn This study LiMn 1.5 Co This study LiMnCo This study LiMn.5 Co This study LiCoO This study Co 2.25 Cr ~ b [6] MnO x c [7] CoO x c [7] Ni.75 Co.25 O x c [7] Ni.9 Fe.1 O x c [7] a,b The mass activities are recorded at a) η = 379 mv, b) η = 35 mv, and c) η = 3 mv. 15

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