Zanling Huang,Xia Zhao,Hong Xia,Fushen Lu,Liangsheng Hu,Paul K. Chu
Photocatalysis has attracted worldwide attention in the fields of energy storage and environmental remediation. However, the solar-to-energy conversion efficiency is still low due to fast charge carrier recombination in the bulk phase of conventional photocatalysts. Herein, a series of photocatalysts including g-C 3 N 4 (GCN), non-polar MgO(110)/GCN composite, MgO(110)+GCN mixture, polar MgO(111)/GCN composite, and MgO(111)+GCN mixture are prepared and their photocatalytic activities are investigated systematically. The polar and non-polar MgO improve the photocatalytic properties of GCN in the following order: MgO(111)+GCN>MgO(110)/GCN>MgO(111)/GCN>MgO(110)+GCN>GCN. Benefiting from charge carrier separation rendered by the local electric field (LEF) induced by MgO(111) polarization, MgO(111) improves the performance of GCN significantly when it is mixed with GCN. However, the enhancement effects are reduced when it is combined with or integrated into GCN as in the MgO(111)/GCN composite, where the traditional heterojunction effect constitutes the main enhancement mechanism. Our study reveals that the photocatalytic enhancement by the LEF effect is superior to that by the traditional heterojunction effect based on polar supporting materials. Our results offer insights into the enhancement mechanism of photocatalysts with polar supporting materials and reveal a simple strategy to optimize photocatalytic processes to exploit solar energy efficiently.
Jun Chen,Shuanghong Tian,Lingjun Kong,Yuting Tu,Jiang Lu,Ya Xiong
An integrated heterogeneous catalytic ozonation and membrane separation system was studied for continuous degradation of refractory organic pollutants in water. MgO nanosheets with dominant (111) facets showed large amounts of medium and strong basic sites due to the particular structure of alternating monolayers of exclusively oxygen and exclusively magnesium atoms. MgO(111) acted as the ozonation catalyst for the first time, it was found that efficient degradation of nitrobenzene was achieved with 25.0 mmol/L of MgO(111) catalysts in a wide pH range of 4.0–12.0. In view of practical application, engineering problems to recover fine size catalysts from the treated water were resolved by applying membrane separation technology in the system. Experimental results showed that the membrane could successfully intercept MgO(111) particles in the reactor by the synergistic cooperative sieving of the bare and dynamic membranes. The long-term continuous experiments demonstrated that the removal rate of nitrobenzene could maintain over 90% with a constant flux of 3.92 L m−2 min−1 during the 24 h operation. The continuous system provides a new method for practical application of heterogeneous catalytic ozonation to remove refractory organic pollutants.
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