Supplementary Information

Transcription

1 Supplementary Information Supplementary Figures 1 nm 1 nm Supplementary Figure S1. SEM images of intermediate products. Intermediate product for Ni(OH) 2 /MWNT after the first step of synthesis at 8 C. Intermediate product for FeO x /graphene after the first step of synthesis at 8 C. 2 nm Supplementary Figure S2. Freely grown Ni(OH) 2 nanoplates. SEM image of free Ni(OH) 2 synthesized using the same procedures as for the Ni(OH) 2 /MWNT hybrid but without any oxidized MWNT added.

2 Current (A) Current (A) Ni foam conditioning Ni foam conditioning + activation NT-Ni conditioning NT-NI conditioning + activation Supplementary Figure S3. Conditioning and activation of Ni(OH) 2 /MWNT. CV curves of blank Ni foam (~1cm 2 ) and Ni foam (1cm 2 ) loaded with ~3mg of Ni(OH) 2 /MWNT after conditioning and activation steps as described in the Methods section of the main text. Scan rate was 4mV/s HER Fe(II) to Fe() Fe(III) to Fe(II) 1st 2nd 5th 11th 2th Fe() to Fe(OH) ads Fe(OH) ads to Fe(II) Fe() to Fe(II) Fe(II) to Fe(III) Supplementary Figure S4. Conditioning of FeO x /graphene. Initial CV scans of the FeO x /graphene hybrid electrode in 1M KOH. Mass loading of the hybrid material was ~.7mg/cm 2.

3 Capacity (mah/g) Capacity Retention Capacity (mah/g) Capacity (mah/g) Supplementary Figure S5. TEM image of FeO x /graphene after initial conditioning cycles. No big metallic Fe particles were observed. To prepare the TEM sample, a FeO x /graphene electrode after conditioning cycling was washed with water and sonicated in ethanol for 5min, and then the ethanol suspension was drop dried onto a TEM grid. 2 nm 4 3 6M KOH 1M KOH.5M KOH Cycle Number Fe/C = 1/2 Fe/C = 1/4 5 1 Cycle Number 1 cycles 2 cycles 3 cycles without glucose with glucose Cycle Number Annealing Temperature ( O C) Supplementary Figure S6. Optimization of the FeO x /graphene electrode. Specific capacity of FeO x /graphene electrodes over cycling in KOH solutions with various concentrations. The electrodes were prepared without glucose and annealed in Ar at 325 C for 1h. Specific capacity of FeO x /graphene electrodes with different Fe/C ratios over cycling in 1M KOH. The electrodes were prepared without glucose and annealed in Ar at 325 C for 1h. Specific capacity over cycling of FeO x /graphene electrodes with and without glucose added in the annealing step at 55 C. Specific capacity over cycling of the FeO x /graphene electrodes with glucose added and annealed at various temperatures. Mass loading of the hybrid material was ~.7mg/cm 2 for all the electrodes..5

4 Supplementary Figure S7. FeO x /graphene after 3 cycles. SEM image of FeO x /graphene electrode materials without (a, b) and with (c, d) glucose after 3 CV cycles in 1M KOH. To prepare the SEM samples, the FeO x /graphene electrodes after cycling were washed with water and sonicated in water for 5min, and then the suspension was drop dried onto a piece of Si chip. 1µm 2nm Supplementary Figure S8. FeO x /graphene after >1 cycles. SEM images of a FeO x /graphene hybrid with glucose after more than 1 electrochemical cycles in 1M KOH. To prepare the SEM sample, the FeO x /graphene electrode after cycling was washed with water and sonicated in water for 5min, and then the suspension was drop dried onto a piece of Si chip.

5 Current (A) Specific Capacitance (F/g) Current (A) Specific Capacitance (F/g) Specific Capacity (mah/g) mg NT-Ni (I) and 1.6mg G-Fe (II) 1.9mg NT-Ni (I) and 1.5mg G-Fe (II) 2.7mg NT-Ni (II) and 1.9mg G-Fe (II) 2.mg NT-Ni (III) and 1.4mg G-Fe (II) 2.mg NT-Ni (III) and 1.4mg G-Fe (IV) 3.mg NT-Ni (III) and 2.1mg G-Fe (IV) 3.mg NT-Ni (V) and 2.1mg G-Fe (VI) I: pasted with 1% MWNT and 1% PVDF II: pasted with 1% CB and 1% PVDF III: drop-dried with 2% PTFE IV: drop-dried with 5% PTFE V: drop-dried with 1% MWNT and 2% PTFE VI: drop-dried with 1% MWNT and 5% PTFE Supplementary Figure S9. Performance of ultra-ni-fe batteries made from Ni(OH) 2 /MWNT and FeO x /graphene with various mass loadings and different electrode preparation methods. All the FeO x /graphene electrodes were prepared with ~2w% of glucose and ~5w% PTFE (or ~1w% PVDF) added and annealed in Ar at 55 C for 1h before measurement mV/s 4mV/s 2mV/s 1mV/s 5mV/s mg/cm 2 2.6mg/cm 2 9.6mg/cm mV/s 4mV/s 2mV/s 1mV/s 5mV/s Voltage (V) Supplementary Figure S1. Activated carbon supercapacitor. CV curves at various scan rates of an activated carbon electrode with a loading of ~9.6mg/cm 2 in 1M KOH. Average specific capacitance within a voltage range of 1V (from V to -1V vs. SCE) of the activated carbon electrode at various scan rates based on CV data in. CV curves at various scan rates of a supercapacitor made from two activated carbon electrodes with loadings of ~9.6mg/cm 2 each in 1M KOH. Average specific capacitance (based on total mass of two electrodes) of the two-electrode activated carbon supercapacitor at various scan rates based on CV data in. Electrode preparation is described in the Methods section of the text.

6 Power (mw/cm 2 ) Specific Power (kw/kg) Energy (mwh/cm 2 ) Specific Energy (Wh/kg) Supplementary Figure S11. Comparison of an ultra-ni-fe cell to an activated carbon supercapacitor. Comparing an ultra-ni-fe cell made from 2.7mg/cm 2 of Ni(OH) 2 /MWNT and 1.9mg/cm 2 of FeO x /graphene to a symmetrical supercapacitor made from two 9.6mg/cm 2 of activated carbon electrodes in device energy, specific energy, device power and specific power. All the electrodes had an area of 1cm 2. The ultra-ni-fe cell calculated here was the one with green symbol in Figure S9.

7 Current (A) Specific Capacity (mah/g) Current (A) Specific Capacity (mah/g) mV/s 2mV/s 1mV/s 5mV/s Ni(OH) 2 CB mix Ni(OH) 2 /MWNT FeO x CB mix FeO x /graphene mV/s 4mV/s 2mV/s 1mV/s Supplementary Figure S12. Comparison of hybrid materials to simple mixtures with carbon black. CV curves at various scan rates and corresponding average specific capacity of free Ni(OH) 2 nanoplates (a, b) and FeO x nanoparticles (c, d) mixed with carbon black (CB). Mass loading was ~.8mg/cm 2 for Ni(OH) 2 and ~.56mg/cm 2 for FeO x. Preparation of the electrodes is described in the Methods section of the text.