Synthesis and Photocatalytic Activity of Cu2O Microspheres upon Methyl Orange Degradation

Abstract

Cuprous oxide (Cu2O) microspheres were synthesized through a simple chemical method by using ascorbic acid (AA) as reducing agent at room temperature and short reaction time. The influence of the reducing agent and ammonium hydroxide (NH4OH), as well as reaction time, on the morphology, size, and crystalline phase structure of Cu2O were explored. The obtained materials were characterized by X-ray diffraction, scanning electron microscopy, nitrogen physisorption, and temperature-programmed reduction, whereas the catalytic activity was assessed using the photodegradation of methyl orange (MO). It was found that AA was responsible for the Cu2O nanoparticles self-assembling into Cu2O microspheres after 0.16 h of reaction time. Quantum theoretical calculations revealed that self-assembly is due to the hydrophilic modification of the Cu2O-nanoparticles driven by the parallel-to-surface dehydroascorbic acid chemisorption; likewise, the simulation of a mesoscopic molecular dynamics confirmed that the amphiphilic-like nature of the dehydroascorbic acid-Cu2O complexes leads to nanoparticles’ spherical morphology. The NH4OH concentration affected the porosity and crystalline phase of the microspheres. The porous Cu2O microspheres modified into well-defined Cu0 polyhedrons with the reaction time. The Cu2O microspheres exhibited high photocatalytic activity up to 76% during decolorization of MO. Two catalytic processes were distinguished: the removal of organic compound controlled by the faceting of the particles under dark conditions, and its photodegradation using visible light increased by the porosity of the Cu2O microspheres.