Highly Efficient Piezo-Catalysis of the Heat-Treated Cellulose Nanocrystal for Dye Decomposition Driven by Ultrasonic Vibration

In this work, the cellulose nanocrystal (CNC) heat-treated in an air atmosphere at 300 °C shows the enhanced piezo-catalytic performance in Rhodamine B (RhB) dye decomposition. Under 180 min ultrasonic vibration with the power of 180 W and the frequency of 40 kHz, the piezo-catalytic decomposition ratio of the heat-treated CNC for RhB (5 mg/L) can reach ∼ 96.65%, far exceeding the 34.58% of the raw CNC. The improvement of the piezo-catalytic performance of the heat-treated CNC is attributed to the introduction of oxygen vacancy defects, which can cause the destruction of crystal structure symmetry and promote the carrier separation, resulting in the enhancement of piezoelectric effect of the heat-treated CNC. The free radical scavenger experiments confirm that the main active specie involved in piezo-catalysis is superoxide radical. Three recycling utilization results show that the decomposition ratio of RhB dye remains about 95% without significant loss, indicating that the heat-treated CNC possesses the good durability and high efficiency in piezo-catalysis. The introduction of oxygen vacancy defects into CNC to obtain the marvelous piezo-catalytic performance is expected to show broad application prospects in the catalytic treatment of dye wastewater.