Cu₂O/CuO heterojunction microplates for enhancement of photocatalytic efficiency

Efficient photocatalysts for removing organic pollutants have attracted significant attention due to their crucial role in addressing environmental and energy challenges. Developing advanced and nontoxic photocatalytic materials with high efficiency under visible light is critical for realizing their full potential in these applications. To address these problems, we synthesized environmentally friendly photocatalytic materials based on low-cost and nontoxic copper (Cu) oxide microplates to decompose organic pollutants efficiently. The chemically synthesized Cu microplates were controllably oxidized to construct various copper oxide microplate structures. As the oxidation temperature increased from 220 to 330°C, the Cu microplates were transformed and evolved through the sequence Cu₂O, Cu₂O/CuO, and CuO phases, respectively. At the temperature range between 270 and 300°C, the microplate with Cu₂O/CuO heterojunction was formed as a core–shell structure due to the diffusion-controlled oxidation process. The formation mechanism of the heterostructured Cu oxide microplates is proposed based on the thermal, chemical, and structural investigations. The Cu₂O/CuO heterojunction formed at 300°C exhibited the most efficient photocatalytic efficiency, achieving a 40% decomposition within 4 h in dissolving a representative organic dye-based pollutant, methylene blue. This optimal pollutant degradation is attributed to the heterojunction structure of Cu₂O/CuO, which inhibited electron–hole pair recombination and provided increased active sites for photocatalytic reactions. Therefore, the heterostructured microplates provided superior catalytic efficiency under visible light while being nontoxic and environmentally sustainable.