Facet-Engineered Cu₂O Microparticles on Graphitic Carbon Nitride Nanosheets as Z-Scheme Heterojunction Photocatalysts for Degradation of Tetracycline

Optimizing the photocatalytic efficiency of semiconductor materials is capable of being achievable by the effective tuning of the interfacial transport efficiency of photogenerated carriers utilizing crystal facet engineering. This study adopted a liquid deposition routine tackle to generate cubic, truncated octahedral, and octahedral Cu 2 O crystals with various exposed facets. Afterward, a Cu 2 O/g-C 3 N 4 heterojunction was constructed exploiting defective g-C 3 N 4 as a carrier. By controlling the exposed facet, the work function difference between Cu 2 O and g-C 3 N 4 was adjusted, resulting in an enhanced built-in electric field and greater photogenerated carrier transit via the Cu 2 O/g-C 3 N 4 heterojunction interface. The OCN heterojunction, which is composed of g-C 3 N 4 and octahedral Cu 2 O with a {111} facet, revealed the highest photocatalytic degradation effectiveness of tetracycline (90.8%), which exceeded the values of pure octahedral Cu 2 O and g-C 3 N 4 by 1.26 and 1.75 times, respectively, as determined by photocatalytic activity experiments. Z-scheme heterojunction among g-C 3 N 4 and octahedral Cu 2 O has been verified through UPS, XPS, EIS, and transient photocurrent response analysis, along the direction of the built-in electric field recognized between them. In contrast, OCN displayed the highest photocatalytic activity due to its Z-scheme heterojunction, which evidently promoted the separation efficiency of photogenerated carriers. This research proposes an innovative approach for regulating the exposed facet of semiconductors and augmenting the inherent electric field strength of heterojunctions, culminating in the efficient photocatalytic degradation of tetracycline.