Electrocatalytically active cuprous oxide nanocubes anchored onto macroporous carbon composite for hydrazine detection

Hydrazine High-Performance Oxidation and Sensing Using a Copper Oxide Nanosheet Electrocatalyst Prepared via a Foam-Surfactant Dual Template

“…Note that the oxidation peak currents linearly increased against the square root of the potential scan rates (υ 1/2 ) with the regression equation (Ipeak = 1.57x + 4.16 and regression coefficient (R 2 ) = 0.999), as shown in Figure 4d. This behaviour was consistent with the hydrazine oxidation at CuO-NS that occurred via the four-electron transfer and mainly via a diffusion-controlled process [60][61][62][63].…”

“…The cyclic voltammetry and impedance results indicate that the CuO-NS electrode showed a significant oxidation performance and faster charge transfer during the electrocatalytic hydrazine oxidation reaction compared with the bare -CuO electrode, which could be related to the nanosheet architecture with an enhanced surface area and electron transfer kinetics [ 60 , 61 , 62 , 63 ]. Based on recent studies, the mechanism of hydrazine oxidation by the electrocatalytic process significantly depends on the electrode surface nature and the electrolyte solution [ 60 , 61 , 62 , 63 ]. In the case of the CuO electrode in an alkaline solution, the mechanism could be proposed to proceed via the irreversible reactions of the hydrazine oxidation at the CuO electrode where the formed intermediate complex of hydrazine in Equation (1) is oxidized at the CuO-NSs surface, producing the N 2 gas as described by Equations (2) and (3).…”

“…Moreover, the correlation between the oxidation peak current and the hydrazine concentration showed two regions of the linear range, as shown in Figure 4 b. The first region’s concentration ranged from 1.0 to 5.0 mM, and the second region’s concentration ranged from 10.0 to 45.0 mM with an oxidation current sensitivity of 0.76 mA/cm 2 mM and 1.06 mA/cm 2 mM, respectively, indicating a high electrocatalytic activity of CuO-NS towards the hydrazine oxidation because of the nanosheet architecture with a high surface area and the presence of a porous network that facilitated the hydrazine diffusion [ 60 , 61 , 62 , 63 ]. Moreover, the presence of two dependent linear equations for the correlation between the oxidation peak current and the hydrazine concentration could be related to the variation in the hydrazine/hydroxide ratio and the adsorption competition between hydrazine/hydroxide ions as well as the oxidation mechanism and rate-determining step, in addition to the N 2 gas formation at the catalytic active sites of the CuO-NS catalyst [ 60 , 61 , 62 , 63 , 64 , 65 ].…”

“…where σ is the background current standard deviation before hydrazine addition and S is the slope of the calibration plot of hydrazine. The achieved limit of detection (LOD) of hydrazine at the CuO-NS electrode reached 15 μM, which was significantly lower than that of the different nanostructure electrode materials reported in the literature [60][61][62][63]. Table 2 summarises the hydrazine sensitivity, linear range, and limit of detection (LOD) for the other electrode materials reported in the literature.…”

“…In addition, the decrease in the hydrazine oxidation current above a catalyst loading of >250 μg could be attributed to the retardation of the electron transfer and the active ion diffusion within the thicker catalyst film. The cyclic voltammetry and impedance results indicate that the CuO-NS electrode showed a significant oxidation performance and faster charge transfer during the electrocatalytic hydrazine oxidation reaction compared with the bare-CuO electrode, which could be related to the nanosheet architecture with an enhanced surface area and electron transfer kinetics [60][61][62][63]. Based on recent studies, the mechanism of hydrazine oxidation by the electrocatalytic process significantly depends on the electrode surface nature and the electrolyte solution [60][61][62][63].…”