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The Electrochemical Reactions Of Ni

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3.1.2 Formation of NiOOH onto SPNE Ni pastes of SPNE were electrodeposited by CV to form Ni(OH)2 and NiOOH as the sources of Ni(II) and Ni(III) ions, respectively, onto the SPNE for 30 cycles from 0 to 1.5 V in 0.1 M NaOH. In the first scan, redox couple peaks of SPNE appeared at 0.614 V. The redox couple peaks of Ni(II)/Ni(III) onto SPNE appeared at 0.538 V (Figure 1(a)). This result shows that Ni(II)/Ni(III) formed well. Moreover, the electrochemical reactions of Ni(II)/Ni(III) redox couples have been reported as follows:[28] Ni + 2OH- → Ni(OH)2 + 2e- Ni(OH)2 + OH- → NiOOH + H2O + e- The CV of the electrodeposited SPNE in 0.1 M NaOH showed one pair of quasi-reversible redox peaks at E1/2 = 0.538 V vs. Ag/AgCl, as shown in Figure 1 (b). The current density on the SPNE is also shown in the inset of Figure 1(b) as a function of the scan rates. The inset in Figure 1(b) shows that the anodic peaks [(Ip)a](r = 0.99462) and the cathodic peaks [(Ip)c](r = 0.99475) of the Ni(OH)2/NiOOH-SPNE electrode increased linearly with the square root of the scan rate (v1/2) in the range of 0.01 to 0.2 V/sec. These results suggest that Ni(II)/Ni(III) in the SPNE is a fast and reversible redox material to investigate the glucose level [29]. 3.1.3 Morphology of SPNE The morphology of SPNE was observed by scanning electron microscopy (SEM). The typical FE-SEM images of the pristine carbon printed ITO electrode and 50 wt% SPNE electrode are shown in Figures 2(a) and 2(b), respectively.

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