Enhanced photocatalytic H2 production of graphitic carbon nitride via implantation of lithium and potassium ions

Photocatalytic water splitting technology using sunlight to produce hydrogen is considered to be an effective method to solve the energy crisis. Graphitic carbon nitride (g-C3N4) as an attractive two-dimensional semiconductor with visible-light response, has been widely applied in water splitting. However, poor light absorption and fast carrier recombination limit the potential application. Herein, the novel g-C3N4 (MCN) embedded by lithium and potassium ions were prepared by the facile molten salt method. Detailed characterizations have proved that the presence of Li+ and K+ could improve the crystallinity and decrease the band gap of g-C3N4, thus effectively promoting carrier separation and expanding light absorption. Theoretical calculation results also have shown that the appearance of Li+ and K+ could significantly reduce the over potential of hydrogen evolution. The MCN exhibits a higher photocatalytic hydrogen evolution rate (239.41 mu mol/h), which is 18.2 times than pure g-C3N4 (13.1 mu mol/h). This work provides a new idea for the design and preparation of novel 2D photocatalysts.