Structure and electrochemical properties of copper wires with seamless 1D nanostructures

A seamless Cu nanowire array grown on Cu wire is prepared by combining thermal oxidation method and electrochemical reduction. The data set described in this paper includes the structure of the Cu nanowires electrode, electrocatalytic active surface area, linear sweep voltammetry and amperometry measurement for nitrate sensing. The electrochemical data show that Cu nanowire arrays exhibited a linear response to nitrate ions over a concentration range from 50 μM to 600 μM (R2 = 0.9974) with a sensitivity of 0.357 μA μM−1 cm−1 and detection limit of 12.2 μM at a signal-to-noise ratio of 3, respectively.

A seamless Cu nanowire array grown on Cu wire is prepared by combining thermal oxidation method and electrochemical reduction. The data set described in this paper includes the structure of the Cu nanowires electrode, electrocatalytic active surface area, linear sweep voltammetry and amperometry measurement for nitrate sensing. The electrochemical data show that Cu nanowire arrays exhibited a linear response to nitrate ions over a concentration range from 50 μM to 600 μM (R 2 ¼ 0.9974) with a sensitivity of 0.357 μA μM −1 cm −1 and detection limit of 12.2 μM at a signal-to-noise ratio of 3

Value of the data
Growth of nanowire arrays on Cu wires by combing thermal oxidation and electrochemical reduction.
Using high-density seamless nanowire array grown on Cu wire as nitrate electrochemical sensor. Nitrate sensing properties of 1D nanostructured Cu wires.

Data
The data set shows the crystal structure of Cu nanowires ( Fig. 1), electrochemical active surface area ( (Table 1) and stability performance of the Cu nanowires electrochemical sensor ( Table 2).
The XRD patterns of the Cu wires in Fig. 1 show the crystal structural changes at each processing stage. After thermal oxidation, diffraction peaks assigned to CuO and Cu 2 O can be observed and the majority of the peaks belong to Cu 2 O crystal. After electrochemical (EC) reduction, the metallic Cu peaks are well recovered with negligible oxides peaks. Compared to the pristine Cu wires, the diffraction peaks of Cu wires after electrochemical reduction are broader. Fig. 2 shows the CV diagram of Cu electrodes with and without surface nanostructures in N 2 purged NaOH (50 mM) electrolyte. The oxidation peak of nanostructured Cu wire improved enormously compared with the bare one in the voltage range from − 0.4 V to − 0.2 V. The charge of Cu 2 O formation in bare and nanostructured Cu wire electrodes, calculated by integrating the oxidation peak area, are 0.266 mC and 17.258 mC, respectively. By assuming the required charge quantity to form a monolayer Cu 2 O is 180 μC cm −2 [1], the ESA of pristine Cu wire and Cu-NWs is 1.478 cm 2 and 95.88 cm 2 , respectively.
In Fig. 3(a), no obvious reduction peak is observed over pristine Cu wires electrode in the presence of nitrate. The well-defined reduction peaks of nitrate are found in the potential range of − 0.4 to − 0.5 V for wires after electrochemical reduction (Cu-NWs). What's more, the peak current rose gradually with the increase of nitrate concentration.

Preparation of Cu nanowires electrode
Cu wires of 0.2 mm in diameter were prepared by wire-drawing under room temperature using pure copper. In a typical preparation, Cu wires were sonicated in 1 M HCl solution for 3 min and then put into deionized water for 3 min to remove surface oxide impurities. The Cu wires were annealed in air at 600°C for 4 h with a heating rate of 10°C/min. The metallic copper nanowire arrays were then obtained using electrochemical reduction method at − 0.4 V (vs. RHE) in 0.1 M KOH solution purged with N 2 gas. Copper oxide nanowires were completely reduced when the cathodic current reached a stable, near-zero horizontal.

Electrochemical measurement
Electrochemical measurements were conducted on a Zahner potentiostat in a three-electrode configuration, with platinum net as counter electrode and SCE as the reference electrode. The electrolyte was purged with N 2 gas before measurement. The as-prepared Cu wires were cut into 5 cm for the measurement. Electrocatalytic active surface area (ESA) of the work electrode was measured through cyclic voltammetry (CV) in a 50 mM NaOH electrolyte at 5 mV s −1 . Linear sweep voltammetry (LSV) was employed to characterize the ability of electrodes for nitrate reduction at 40 mV s −1 . Amperometry (IT) measured at a constant − 0.46 V (vs. SCE) was used to detect the concentration of nitrate in water. Both of the LSV and IT were carried out in a 0.1 M Na 2 SO 4 electrolyte at pH ¼ 2.