Experiment On Scanning And Tunneling Electron Microscopy ( Sem ) Images Of
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Fig. 1 shows scanning and tunneling electron microscopy (SEM and TEM) images of
(a,c) MWCNT and (b,d) Ni NP-MWCNT.
Figure 1: Scanning electron microscopy (SEM) images of (a) MWCNT and (b) Ni NP-MWCNT and transmission electron microscopy (TEM) images of (c) MWCNT and (d) Ni NP-MWCNT electrodes.
The image in Fig. 1a shows that the MWCNTs form a dense and open matrix of high surface area. The MWCNTs are 4-5 µm in length and 60-100 nm in diameter. The presence of Ni NPs on the MWCNT surfaces in Fig. 1b does not influence the structure of the MWCNT matrix, leaving it quite open and accessible to the electrolyte. In order to clearly show the presence of Ni NPs on the MWCNTs, transmission electron microscopy was conducted. Fig. 1c shows a TEM image of MWCNT prior to deposition of Ni NPs by PLA. The walls of the MWCNT are smooth and void of any observable NPs. Fig. 1d contrasts the TEM image shown in Fig. 1c by displaying a Ni NP-decorated MWCNT. It can be seen that the Ni NPs are uniformly distributed along the MWCNT, covering the entire surface. The Ni NPs are shaped as ‘nano-flakes’.
3.2 Electrochemical regeneration of 1,4-NADH Potentiostatic (electrolysis) experiments were conducted in a batch electrochemical reactor operated at various electrode potentials ranging from −1.40 V to −1.70 V, in order to investigate (i) the NAD+ reduction kinetics and (ii) the electrocatalytic efficiency of Ni NP-MWCNT electrode in the regeneration of enzymatically-active