Synthesis and Photocatalytic Activity of Cu₂O Microspheres upon Methyl Orange Degradation

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.