Supporting Information. High-Performance Supercapacitor

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1 Supporting Information Mesoporous CoO Continuous 3D Porous Carbon Skeleton of Rose Based Electrode for High-Performance Supercapacitor Danni Lan, Yangyang Chen, Pan Chen, Xuanying Chen, Xu Wu, Xuli Pu, Yan Zeng and Zhihong Zhu* : Institute of Nano-Science and Nano-Technology, College of Physical Science and Technology, Central China Normal University, Wuhan, , P. R. China zhzhu@phy.ccnu.edu.cn. : Xiamen Entry-Exit Inspection and Quarantine Bureau of the People's Republic of China, Xiamen, 36102, P. R. China Experimental Section 1. Materials All solvents and chemicals were used as received without further purification. Cobalt nitrate (Co(NO 3 ) 2 6H 2 O), ammonium fluoride (NH 4 F) and urea ((NH 2 ) 2 CO) were obtained from 1

2 shanghai chemical reagent Co. Cetyltrimethylammonium (CTAB) was purchased from Tianjin chemical reagent Co. All aqueous solutions were freshly prepared with deionized water. Preparation of continuous 3D porous carbon skeleton of rose The preparation process is very simple. Firstly, tearing off one side skin of the fresh rose by tweezers and then the skin on another side can be easily removed after the freeze drying. The freeze dried roses were finally carbonized at 500 in nitrogen atmosphere for 4 h with a heating rate of 10 per minute. Then, the ideal 3D porous carbon skeleton of rose was obtained. Synthesis of mesoporous CoO continuous 3D porous carbon skeleton of rose In a typical procedure 1, Co(NO 3 ) 2 6H 2 O (4 mm ), NH 4 F (16 mm), CTAB (2 mm) and (NH2) 2 CO (40 mm) were added into 200 ml deionized water by vigorous stirring at room temperature for 30 min to get a homogeneous solution, then the solution was transferred into a 100 ml Teflon-lined stainless steel autoclave. A piece of as-prepared carbon scaffold was then put into the reaction solution; the autoclave was sealed and maintained at 120 for 16 h. After cooling down to room temperature naturally, the product was picked up and rinsed for several times with distilled water and ethanol to remove the surface attached debris and residual reactants. The product was dried at 60 and converted to CoO at 350 in nitrogen atmosphere for 3 h with a heating rate of 4 per minute. All materials were weighted by analytical microbalance. 2. Characterization Structures and Morphologies The structures and morphologies of both the precursor and product were characterized by X- ray diffraction (XRD, X'Pert PRO MRD, PANalytical, Netherlands), X-ray photoelectron 2

3 spectroscopy (XPS) (AXIS-ULTRA DLD-600W). Raman spectroscopy (LabRAMHR evolution, 532 nm), field-emission scanning electron microscopy (SEM; JEOL, JSM-6700F), highresolution transmission electron microscopy (TEM; JEM-2100(HR), 200 kv) and N 2 adsorptiondesorption measurements using an BELSORP-mini surface area of analyzer. The pores Brunauer-Emmett-Teller (BET) method was used to calculate the specific surface area of samples. The pore size distributions (PSD) were derived from the desorption branch of the isotherm with the Barrett-Joyner-Halenda (BJH) method. Electrochemical measurements The electrochemical measurements were carried out in a typical three-electrode electrochemical system composed of a working electrode, a platinum plate as auxiliary electrode and a saturated calomel electrode (SCE) as reference electrode. The electrolyte is 2 M KOH aqueous solution. To make the working electrode, nickel foams were washed with distilled water and ethanol to serve as the current collector, then the prepared monolithic composite without grinding and other additives was sandwiched into the nickel foams, and after pressed, it was directly used as the working electrode. Cyclic voltammetry (CV) measurements and galvanostatic charge-discharge were performed on a CHI440a electrochemical workstation (Chenhua, Shanghai). CV measurements were carried out in a voltage window between 0 V and 0.6 V at different scanning rates. The galvanostatic charge-discharges (CD) were measured over the potential range from 0 V to 0.45 V. All the measurements were done under the room temperature. The specific capacitance was calculated by the following equation 2-3 : C = I t m V (1) 3

4 Where I in ma is the charge-discharge current density, m in mg, V in V and t in s represented the mass of active materials, the potential window and the charge-discharge time, respectively. Energy density (Wh/kg) was derived as: E= 1 C V (2) Where C is the measured device capacitance, and V was the voltage across the electrode. The power density (W/kg) was expressed as: P= 3600E t (3) Where E was the energy density and t (s) was the discharge time. 3. Results and discussion 4

5 Figure. S2 TEM image of the composite, inset is the SAED images of a single CoO nanocube. Wrinkled surfaces of the rose carbon skeleton as well as the homogeneous nanocubic structure can be clearly seen from Figure. S2, the selected area electron diffraction (SAED) patterns in inset give the polycrystalline nature of the cubic CoO. Figure. S3 Galvanostatic charge-discharges (CP) curves at the current density of 40 A/g. 5

6 A specific capacitance of 521 F/g can still be obtained if the current density up to 40 A/g. Figure. S4 (a) CV curves of the mesoporous CoO continuous 3D porous carbon skeleton of rose composite, physical mixture of pre-synthesized CoO and carbon scaffold and bare nickel foam at a scanning rate of 10mV/s; (b) Corresponding galvanostatic charge-discharge curves at 1A/g. Compared with the mesoporous CoO continuous 3D porous carbon skeleton of rose electrode, CV integrated area of the physical mixture of pre-synthesized CoO and carbon scaffold is quite small, which highlights our work. And the integrated area of pure nickel foam can be negligible, revealing almost no capacitance contribution to the as-prepared electrode (Figure S4a). This is also confirmed in the charge-discharge measurement from Figure. S4b, where the specific capacitance can be calculated 1672 F/g for Rose, 457 F/g for CoO and Rose, 60 F/g for bare Ni foam. 6

7 Figure. S5 SEM image of mesoporous CoO continuous 3D porous carbon skeleton of rose after 3000 cycles. From the SEM image we can see the morphology and structure of CoO nanocubes after 3000 cycles can be largely retained with only slight aggregation after the long time process of charging/discharging, which contributes to the 82% capacitance retention. Of course, it can be seen that the structure of CoO nanocubes collapsed to some degree, which would affect its redox reaction efficiency, leading to the capacitance loss finally. REFERENCES 1. Guo, C.; Zhang, X.; Huo, H.; Xu, C.; Han, X., Co 3 O 4 Microspheres with Free-Standing Nanofibers for High Performance Non-Enzymatic Glucose Sensor. Analyst 2013, 138 (22), Deori, K.; Ujjain, S. K.; Sharma, R. K.; Deka, S., Morphology Controlled Synthesis of Nanoporous Co 3 O 4 Nanostructures and Their Charge Storage Characteristics in Supercapacitors. ACS applied materials & interfaces 2013, 5 (21), Ma, S.-B.; Nam, K.-W.; Yoon, W.-S.; Yang, X.-Q.; Ahn, K.-Y.; Oh, K.-H.; Kim, K.-B., A Novel Concept of Hybrid Capacitor Based on Manganese Oxide Materials. Electrochemistry Communications 2007, 9 (12),