Energy level alignment and exciton dynamics at the H₂O/g-C₃N₄ interface for photocatalytic water splitting

【作者】 马慧中； 马玉臣；

【机构】 山东大学化学与化工学院；

【摘要】 Graphitic carbon nitride（g-C₃N₄） has drawn increasing attention due to its hydrogen reduction capability under visible light. We investigate the energy level alignment at the H₂O/g-C₃N₄ interface within the many-body Green’s function theory[1,2] and the decay of electron-hole pair by the time-dependent Schr鰀inger equation[3]. We find that the highest occupied molecular orbital of water molecule is much deeper in energy than that of g-C₃N₄, while the electronic level of OH. appears at the top of the valence band of the whole system. This means that the photon-induced hole from g-C₃N₄ cannot migrate to the neutral H₂O but the OH. instead. However, if taking into account the interaction between electron and hole, the hole cannot stay stably on the OH.but be still mostly confined in g-C₃N₄ since the lowest excited state of the H₂O/g-C₃N₄ interface is with the hole delocalized on g-C₃N₄. This may explain why the quantum efficiency of g-C₃N₄ for hydrogen production is very low.There is also some probability for the electron in OH. to be excited to the conduction band of g-C₃N₄ by ultraviolet light, leaving a neutral hydroxyl radical.更多还原

【Abstract】 Graphitic carbon nitride（g-C₃N₄） has drawn increasing attention due to its hydrogen reduction capability under visible light. We investigate the energy level alignment at the H₂O/g-C₃N₄ interface within the many-body Green’s function theory[1,2] and the decay of electron-hole pair by the time-dependent Schr鰀inger equation[3]. We find that the highest occupied molecular orbital of water molecule is much deeper in energy than that of g-C₃N₄, while the electronic level of OH. appears at the top of the valence band of the whole system. This means that the photon-induced hole from g-C₃N₄ cannot migrate to the neutral H₂O but the OH. instead. However, if taking into account the interaction between electron and hole, the hole cannot stay stably on the OH.but be still mostly confined in g-C₃N₄ since the lowest excited state of the H₂O/g-C₃N₄ interface is with the hole delocalized on g-C₃N₄. This may explain why the quantum efficiency of g-C₃N₄ for hydrogen production is very low.There is also some probability for the electron in OH. to be excited to the conduction band of g-C₃N₄ by ultraviolet light, leaving a neutral hydroxyl radical.更多还原