Morphology Control and Photocatalysis Enhancement by in Situ Hybridization of Cuprous Oxide with Nitrogen-Doped Carbon Quantum Dots

Cuprous oxide (Cu₂O) is an attractive photocatalyst because of its visible-light-driven photocatalytic behavior, abundance, low toxicity, and environmental compatibility. However, its short electron diffusion length and low hole mobility result in low photocatalytic efficiency, which hinders its wider applications. Herein, we report an in situ method to introduce nitrogen-doped carbon dots (N-CDs) into Cu₂O frameworks. It is interestingly found that the introduction of N-CDs drives the morphology of N-CDs/Cu₂O to evolve from rough cube to sphere, and the most encouraging result is that all of the obtained N-CDs/Cu₂O composites exhibit better photocatalytic activities than pure Cu₂O cubes. The optimal N-CDs/Cu₂O photocatalyst is synthesized with 10 mL of N-CDs solution, which shows the best degradation ability (100%, 70 min), far superior to pure Cu₂O cubes (∼5%, 70 min) and P25 (∼10%, 70 min). Beside the photodegradation of methyl orange, N-CDs/Cu₂O₍₁₀₎ composites also exhibit excellent photocatalytic activities in the photodegradation of methyl blue and rhodamine B. It is demonstrated that the excellent photocatalytic performance of N-CDs/Cu₂O composites can be attributed to the highly roughened structure and the suppression of electron–hole recombination as a result of the introduction of N-CDs. These findings demonstrate that the conjugation of CDs is a promising method to improve the photocatalytic activities for traditional semiconductors.