Effect of the Cu foam pretreatment in the growth and inhibition of copper oxide nanoneedles obtained by thermal oxidation and their evaluation as photocathodes. (1st November 2019)

• Record Type: Journal Article
• Authors: Carrera-Crespo, J. Edgar; Huerta-Flores, Ali M.; Torres-Martínez, Leticia M.; Juárez-Ramírez, Isaías
• Is Part Of: Materials science in semiconductor processing. Volume 102(2019)
• Publication Date: 2019-11-01
• Subjects: Copper oxide nanoneedles -- Thermal oxidation -- Growth mechanism -- Substrate pretreatment; Semiconductors -- Periodicals; Integrated circuits -- Materials -- Periodicals; Semiconducteurs -- Périodiques; Circuits intégrés -- Matériaux -- Périodiques; Electronic journals; 621.38152
• DOI: 10.1016/j.mssp.2019.104604
• Languages: English
• ISSNs: 1369-8001

Abstract

Abstract: Cu2 O-CuO layers were prepared in situ on copper foam substrates by thermal oxidation at 400 °C in air using different pretreatments with acetone, HCl and NaOH. The effect of the pretreatment in the shape and physicochemical properties of the Cu2 O-CuO layers, as well as in the growth or inhibition of the copper oxide nanostructures was studied, and a growth mechanism is proposed. It was found that the pretreatment modulates the nucleation and growth of the copper oxide nanostructures, being the process with NaOH the most suitable to promote the formation of well-defined nanoneedles, while in the case of the samples pretreated with acetone and HCl, copper oxide layers with irregular shape microstructures were obtained. The composition, structural, morphological and optical properties of the copper oxide structures were determined by X-ray diffraction, scanning electron microscopy, UV-vis diffuse reflectance and photoluminescence spectroscopy. The results showed that in all cases, the presence of both copper oxides, Cu2 O and CuO was observed, with an optical band gap of 1.0 and 1.3 eV. The copper oxide structures exhibited photoluminescence emission centered at 551 nm, related to the recombination of the electron-hole pairs in the samples. The materials prepared with a NaOH pretreatment showed the lower emission and recombination rate. Moreover, the 3D Cu-Cu2 O-CuO based materials were evaluated as photocathodes in a 0.5 M Na2 SO4 solution and under Xe lamp illumination. The photoelectrode where 1D nanostructures were grown, exhibited the lower resistance to the charge transference in the Nyquist plots, the highest current density in the linear voltammetry and the highest photoresponse in the on-off light experiments. The improved electrical and physicochemical properties of the samples pretreated with NaOH was related to the particular 1D nanoneedle morphology, which promoted higher conductivity and photoresponse, lower resistance to the charge transference and lower recombination of free charge carriers, demonstrating the potential use of these electrodes for photoelectrochemical applications. Finally, this work proved that it is possible to grow well-defined and highly crystalline CuO nanoneedles on copper foam porous substrates through a simple, fast and clean method. Graphical abstract: Image 1 Highlights: CuO nanoneedles were grown in situ on copper foam by thermal oxidation. Effect of the pretreatment on the metallic substrate surface is studied. Well-defined CuO nanoneedles were obtained by pretreatment with 1 M NaOH. A growth mechanism of the 1D copper oxide nanostructures is proposed. Copper oxide nanoneedles improved the photoelectrochemical performance of Cu-Cu2 O-CuO based photocathodes.