WO3/N-CDs photocatalyst with Z-scheme heterojunction for efficient tetracycline degradation under visible and near-infrared light

Using visible and near-infrared (NIR) light as excitation sources to realize the photocatalytic degradation of environmental pollutants is a promising strategy, which will broaden the application of solar energy, but some challenges still exist. Herein, a novel direct Z-scheme tungsten trioxide/nitrogen doped carbon dots (WO3/NCDs) heterojunction photocatalyst with remarkably enhanced light-absorption and broad-response photocatalytic activity is successfully constructed. The obtained WO3/N-CDs (CDs, 5 wt%) exhibit stronger absorption properties in the NIR region than in the ultraviolet region, and superior degradation efficiency (96.0% within 1 h) towards tetracycline (TC). The reaction rate constant of 5%WO3/N-CDs reaches 0.0428 min(-1), is 15.3 and 7.5 times that of N-CDs and WO3 respectively. The outstanding photocatalytic activity is on account of the intimate Z-scheme heterojunction interfacial contact, which promotes the spatial separation of electron-hole pairs, as well as reduces the barrier of electron transfer. Through morphology orientation, preferential growth of (002) crystal plane is induced, resulting in the formation of hexagonal single crystal structure of WO3, which is conducive to the construction of Z-scheme heterojunction between N-CDs and WO3. According to the analysis of energy band position and free radicals, O-1(2), O-center dot(2)-, and h(+) take part in the degradation process. Overall, this research might enlighten the reasonable construction of heterostructure between new carbon material and semiconductor photocatalyst to realize the utilization of broad-spectrum sunlight.