Insights into enhancement of photocatalytic properties of g-C3N4 by local electric field induced by polarization of MgO(111)

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.