Morphological Control of Mesoporosity and Nanoparticles within Co₃O₄–CuO Electrospun Nanofibers: Quantum Confinement and Visible Light Photocatalysis Performance

Abstract

The one-dimensional (1D) mesoporous and interconnected nanoparticles (NPs) enriched composite CoO-CuO nanofibers (NFs) in the ratio Co:Cu = 1/4 (CoO-CuO NFs) composite have been synthesized by electrospinning and calcination of mixed polymeric template. Not merely the mesoporous composite CoO-CuO NFs but also single mesoporous CoO NFs and CuO NFs have been produced for comparison. The choice of mixed polymer templates such as polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) for electrospinning is responsible for the formation of 1D mesoporous NFs. The HR-TEM result showed evolution of interconnected nanoparticles (NPs) and creation of mesoporosity in all electrospun NFs. The quantum confinement is due to NPs within NFs and has been proved by the surface-enhanced Raman scattering (SERS) study and the UV-vis-NRI diffuse reflectance spectra (DRS). The high intense photoluminescence (PL) spectra showing blue shift of all NFs also confirmed the quantum confinement phenomena. The lowering of PL spectrum after mixing of CuO in CoO nanofibers framework (CoO-CuO NFs) proved CuO as an efficient visible light response low cost cocatalyst/charge separator. The red shifting of the band gap in composite CoO-CuO NFs is due to the internal charge transfer between Co to Co and Cu, proved by UV-vis absorption spectroscopy. Creation of oxygen vacancies by mixing of CuO and CoO also prevents the electron-hole recombination and enhances the photocatalytic activity in composite CoO-CuO NFs. The photocurrent density, Mott-Schottky (MS), and electrochemical impedance spectroscopy (EIS) studies of all NFs favor the high photocatalytic performance. The mesoporous composite CoO-CuO NFs exhibits high photocatalytic activity toward phenolic compounds degradation as compared to the other two NFs (CoO NFs and CuO NFs). The kinetic study of phenolic compounds followed first order rate equation. The high photocatalytic activity of composite CoO-CuO NFs is attributed to the formation of mesoporosity and interconnected NPs within NFs framework, quantum confinement, extended light absorption property, internal charge transfer, and effective photogenerated charge separations.

Facile thermal exfoliation of Cu sheets towards the CuO/Cu2O heterojunction: a cost-effective photocatalyst with visible-light response for promising sustainable applications

“…1A 25 The diffraction peaks at 35.6 and 38.7 are ascribed to the (À111) and (111) diffraction phases of monoclinic CuO (JCPD standard card no.48-1548), respectively. 27 No diffraction peaks of other phases could be observed; this conrmed high purity of the products. Moreover, as illustrated in Fig.…”

Enhanced Visible-Light Photocatalysis of Nanocomposites of Copper Oxide and Single-Walled Carbon Nanotubes for the Degradation of Methylene Blue

“…In addition to these peaks, two characteristic satellite peaks are positioned at 943.83 and 962.65 eV in the spectrum of pure CuO, indicating that the copper in pure CuO is Cu 2+ [20,21]. [20,21]. The C-1s core-level profiles of CuO-SWCNT-5 composite are displayed in Figure 4d.…”

“…The binding energy difference between these two peaks, as calculated from the spectra, is 20.02 eV, which matches the value reported for Cu 2+ in the literature. In addition to these peaks, two characteristic satellite peaks are positioned at 943.83 and 962.65 eV in the spectrum of pure CuO, indicating that the copper in pure CuO is Cu 2+ [20,21]. [20,21].…”

Regulating the Electronic Structure and Water Adsorption Capability by Constructing Carbon‐Doped CuO Hollow Spheres for Efficient Photocatalytic Hydrogen Evolution

“…Hence, the flat‐band potentials of Pure‐CuO and C−CuO HSs were calculated to be 0.54 and 0.35 V (vs. Ag/AgCl electrode), corresponding to 0.76 and 0.57 V (vs. NHE), respectively. The valence band potential of Pure‐CuO and C−CuO HSs were therefore calculate to be 0.76 and 0.57 V (vs. NHE), respectively [22] . It could be clearly observed that the VB potentials of C−CuO HSs was negative than that of Pure‐CuO, indicating that the introduction of C atoms could narrow the band gap of CuO via lifting the VB position.…”