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RESEARCH ARTICLE

Enhanced cyclic performance initiated via an in situ transformation of Cu/CuO nanodisk to Cu/CuO/Cu2O nanosponge Uthirakumar Periyayya 1,2

&

Devendiran Madhu 2 & Kalaiarasan Subramaniyam 2 & Hoki Son 1 & In-Hwan Lee 1

Received: 26 June 2020 / Accepted: 17 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract A simple oxidation method for preparing CuO nanodisks on a flexible Cu sheet is presented. The crystal structure of as-prepared CuO nanodisks was analyzed by X-ray diffraction. The elemental composition and surface morphology were documented by Xray photoelectron spectroscopy, scanning, and transmission electron microscopy. The photocatalytic performance of flexible Cu/ CuO nanodisks was tested to mediate the degradation of RhB and MB dyes. After 2nd recycling, an in situ transformation of the nanodisk surface leads to electron transfer between the conduction bands of Cu2O and CuO phase, accelerating the degradation of the dyes due to a more favorable electron-hole separation under different band gap engineering. The optical and electrochemical impedance analyses were conducted to examine the efficiency of photogenerated charge carrier separation. Additionally, in the photodegradation system of Cu/CuO nanodisks, the generation of superoxide radical (·O2−) is responsible for the dye degradation under daylight irradiation. The generation of the latter radical is energetically feasible since the conduction band of Cu2O (− 0.28 eV) is well-matching with the redox potential of O2/·O2− (− 0.28 eV). Consequently, it is concluded that the cyclic stability shows the usefulness of Cu/CuO nanodisk preparation for the dye degradation under daylight irradiation.

Keywords Flexible Cu/CuO sheet . Cu2O nanosponges . Daylight photocatalyst . Recycle test . Nanocrystalline materials

Introduction Highlights • A facile method is developed to prepare the flexible sheets of Cu/CuO nanodisks. • Excellent photocatalytic performance on RhB and MB dye under daylight irradiation. • In situ transformation facilitates an enhanced photodegradation. • The proposed sheet replaces the conventional nanomaterial photocatalysis. Responsible Editor: Sami Rtimi Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-10910-0) contains supplementary material, which is available to authorized users. * Uthirakumar Periyayya [email protected] * In-Hwan Lee [email protected] 1

Department of Materials Science and Engineering, Korea University, Seoul 02841, South Korea

2

Nanoscience Center for Optoelectronic and Energy Devices [Nano-COED], Department of Chemistry, Sona College of Technology, Salem, Tamilnadu 636005, India

Over the past few years, the advancement of visible light photocatalysts has attracted widespread interest owing to the consumption of visible light to replace the traditional UV-light active photocatalysts (Opoku et al. 2017). Since the natural daylight radiation is abundant and clean energy source, which constitutes ~ 43%