Re-Examination of CuO Reduction Steps and Understanding of the Factors Influencing the Cyclic Voltammetry Profile of CuO

Abstract

Whether CuO reduction is one step or two steps reaction has been argued for several decades, and one step reaction mechanism is mainly supported by CuO CV (cyclic voltammetry) profile, where only one cathodic peak represents the direct reduction from CuO to Cu. However, some researchers support two steps reaction mechanism, because they observed Cu 2 O as intermediate with spectroscopy technique or two cathodic peaks in the CV profile. In this study, two colloid electrodes containing crystal CuO particles are electrolyzed in KCl electrolyte at −1.7 V and −1.65 V respectively, and both of the products are composed of Cu 2 O and Cu. The electrolysis voltage can change the weight ratio of Cu 2 O and Cu, and the electrolysis results firmly prove that CuO reduction is two steps reaction: CuO is reduced to Cu 2 O, then to Cu. Therefore, the rationality of the criterion for determining one step reaction is re-considered in this study. The experimental conditions and parameters, including CV scan rate, atom arrangement of CuO, particle size of CuO, and anions and pH value of electrolyte, are discussed in the present study, and all these factors can affect CuO reduction process, thus influencing the cathotic peaks, such as the number, shape and potential of the peaks in CuO CV profile. It could lead to incorrect conclusion, when CuO reduction steps is determined by the cathode peak without comprehensive consideration of the effect from all these factors. In another word, cathodic peak number in the CV profile sometimes is not a straightforward and appropriate criterion to determine the number of steps of CuO reduction. In addition, S 2− ions is found to be an effective addtive to enhance the cyclic ability and discharge plateau of Cu alkaline battery in this study.

Facile Preparation of Hydrogen-Bonded Organic Framework/Cu2O Heterostructure Films via Electrophoretic Deposition for Efficient CO2 Photoreduction

“…Cu 2 O exhibited two reversible reductive processes at E 1/2 = −0.16 and E 1/2 = −0.42 V vs Ag/ AgCl (yellow dotted line), attributed to the redox of Cu + /Cu and Cu 2+ /Cu, respectively (Figure 4d). 35,36 The Cu 2+ comes from CuO that is on the surface of Cu 2 O, as confirmed by XPS. PFC-45 showed a reversible reduction at E 1/2 = −0.63 V (blue dotted line).…”

Synergy of Charge Storage Properties of CuO and Polypyrrole in Composite CuO-Polypyrrole Electrodes for Asymmetric Supercapacitor Devices

“…Oxides of transition elements, such as Fe, Mn, Co, Ni, and Cu, are promising for energy storage in supercapacitor devices. − The charge storage properties of Fe 3 O 4 , γ-Fe 2 O 3 , MnO 2 , Mn 3 O 4 , Co 3 O 4 , NiO, and CuO are related to changes of the valence of the corresponding metal ions in chemical redox reactions. , CuO offers benefits for supercapacitor applications due to its low cost and chemical stability. Cyclic voltammetry studies , of CuO showed reduction of Cu 2+ to Cu + and Cu + to Cu. This provides a platform for the application of CuO in anodes of supercapacitors .…”

“…1,4 CuO offers benefits for supercapacitor applications due to its low cost and chemical stability. Cyclic voltammetry studies 5,6 of CuO showed reduction of Cu 2+ to Cu + and Cu + to Cu. This provides a platform for the application of CuO in anodes of supercapacitors.…”

Strong Cr–O Hybridization Prevents Active Cu(II) from Cathodic Reconstruction for Alkaline Hydrogen Evolution Catalysis

“…[ 14 ] Inevitably, CuO subsequently transforms into inactive metallic Cu before the HER potential region (Scheme 1c), due to the favorable thermodynamic reduction potential of Cu(II)/Cu. [ 15 ] The weak Cu–O bonding strength endows O sites with high reactivity for active H adsorption, further leading to the escape of O atoms from the CuO surface and followed by the structural collapse from CuO to metallic Cu. [ 16 ] In this regard, stabilizing the O atoms in CuO and weakening the H adsorption on the O site to secure the highly unstable Cu(II) is the key to achieve the theoretical benefits of CuO toward HER catalysis.…”