Supporting Information Co 3 O 4-δ Quantum Dots as a Highly Efficient Oxygen Evolution Reaction Catalyst for Water Splitting Guangxing Zhang, Jie Yang, Han Wang, Haibiao Chen, Jinlong Yang, and Feng Pan School of Advanced Materials, Shenzhen Graduate School, Peking University, Shenzhen 518055, People s Republic of China *Corresponding authors: yangjl@pkusz.edu.cn, panfeng@pkusz.edu.cn. S1
Figure S1. (a) SEM image of mesoporous Co 3 O 4 nanosheets; (b) N 2 sorption isotherms and (c) BJH pore size distribution of mesoporous Co 3 O 4 nanosheets. S2
Figure S2. (a) Full XPS spectra; Binding energy at (b) Li 1s, (c) Co 2p and (d) O 1s for the Co 3 O 4-δ QDs with different cycles and Co 3 O 4 nanosheets. S3
Figure S3. EDLC curves of (a) Co 3 O 4 nanosheets, (b) Co 3 O 4 nanosheets@ni foam, and (c) Co 3 O 4-δ -QDs-20 th cycle respectively with different scan rates. Figure S4. Faraday efficiency test. (a) Water drainage device; (b) Comparison of the measured amount of O 2 and the theoretical amount calculated based on 100% Faradaic efficiency. Constant current of 20 ma cm -2 was used in the experiment. S4
Figure S5. TEM images of the Co 3 O 4-δ -QDs-20 th cycle after OER: (a) Nanosheet morphology consisted of quantum dots; (b) Lattice spacing with the quantum dots. Figure S6. Full XPS spectra for the Co 3 O 4-δ -QDs-20 th cycle before and after OER, as well as Co 3 O 4 nanosheets, inset is binding energy at Li 1s. S5
Figure S7. Nyquist plots for the different galvanostatic cycle Co 3 O 4-δ measured at 1.5 V vs. RHE during the OER at 25 C. 100 80 ir corrected η vs. RHE (V) 0.0 0.1 0.2 0.3 0.4 1.65 Co3O4 nanosheets@ni foam Co3O4 sheet@ni foam Current Density (ma cm -2 ) 60 40 20 ir corrected E vs. RHE (V ) 1.60 1.55 1.50 47.1 mv/dec 20 40 60 80 100 Log (i ma cm -2 ) 0 1.2 1.3 1.4 1.5 1.6 1.7 ir corrected E vs. RHE (V) Figure S8. LSV curves of Co 3 O 4 nanosheets@ni foam at 1 mv s -1 in O 2 -saturated 1 M KOH solution, inset was the Tafel plot of Co 3 O 4 nanosheets@ni foam. S6
Figure S9. Cyclic voltametry curves with scan rate from 3 to 40 mv s -1 for (a) Co 3 O 4 nanosheets and (b) Co 3 O 4-δ -QDs-20 th cycle. Figure S10 Figure S10. Extrapolation of (a) q* Total and (b) q* Outer for different galvanostatic cycle of Co 3 O 4-δ. Table S1. Electrochemical parameters obtained for different galvanostatic cycle of Co 3 O 4-δ. S7
Table S2. Detailed comparison of OER activity for the Co 3 O 4 serials catalysts reported in recent years. Catalysts η@10 ma Tafel slope Mass loading Electrolyte Substrate Ref., year cm -2 (V) (mv dec -1 ) (mg cm -2 ) Co 3O 4 NS 0.33 58 0.25 1 M KOH CNF This work Co 3O 4 NS@Ni Foam 0.31 47 0.25 1 M KOH Ni foam This work Co 3O 4-δ-QDs-20 th cycle 0.27 39 0.25 1 M KOH CNF This work Co 3O 4/N-rmGO 0.31 67 0.17 1 M KOH GC (s1, 2011) Co 3O 4 CuCo 2O 4 0.427 / 0.12 1 M KOH GC (s2, 2013) Ordered Meso-Co 3O 4 0.476 / 0.13 1 M KOH Au foil (s3, 2013) Co 3O 4/GR 0.375 67 / 0.1 M KOH ITO (s4, 2013) Au/Co 3O 4 0.37 60 0.064 0.1 M KOH GC (s5, 2014) N-CG-CoO 0.34 71 0.18 1 M KOH GC (s6, 2014) Co 3O 4/C-NA* 0.22 61 0.2 0.1M KOH Cu foil (s7, 2014) Meso-Co 3O 4 NWs 0.37 72 0.136 1 M KOH GC (s8, 2014) Graphene-Co 3O 4 0.31 49 0.04 1 M KOH GC (s9,2014) CoMn LDH 0.32 43 0.142 1 M KOH GC (s10,2014) Hierarchical CoO x 0.29 75 0.136 1 M KOH GC (s11,2015) Crystalline Co 3O 4 0.3 65 0.04 0.1 M KPi. GC (s12,2015) Co 3O 4 Flakes 0.31 48 0.04 1 M KOH GC (s13,2015) CoO x@cn 0.26 85 1 1 M KOH GC (s14,2015) Rhombus Co 3O 4 0.27 62 / 1 M KOH ITO (s15,2015) Co@ Co 3O 4/NC 0.41 54 0.21 0.1 M KOH GC (s16,2016) Plasma-Engraved Co 3O 4 0.30 68 / 0.1 M KOH Ti foil (s17,2016) Reduced Co 3O 4 0.38 73 0.08 0.1 M KOH GC (s18,2016) CuCo 2O 4/NrGO 0.36 64 0.14 1 M KOH GC (s19,2016) rgo Co 3O 4 YSNC 0.41 85 0.08 0.1 M KOH GC (s20,2016) CoO@N/S-CNF 0.30 95 0.08 0.1 M KOH GC (s21,2016) CoP NS/C 0.277 85.6 0.71 1 M KOH CNF (s22,2016) S8
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