Revealing the effect regularity of cations on electron storage capacity of poly(heptazine imide) in “dark photocatalysis”

Abstract

As a crystalline carbon nitride material, poly(heptazine imide) (abbreviated as PHI) exhibits higher photoinduced charge separation performance than traditional melon-based carbon nitride. The excellent charge separation is mainly attributed to the fact that the photoinduced electrons can be captured by cations (such as K+ and H+) and further stored in the PHI framework with the presence of sacrificial agents (such as methanol). Due to this special property, the stored electrons can be used for delayed H2O2 or H2 production in the “dark photocatalysis” field. Nevertheless, the effect regularity of cations on the electron storage capacity of PHI is still not clear. In this work, this problem has been preliminarily revealed. The electron storage capacity of a series of PHI materials has been quantified by the H2O2 production test in dark conditions. The result indicates that the electron storage capacity of PHI samples shows a volcano curve with the alkali metal ion content. Based on experimental tests and theoretical simulations, it is concluded that the electron storage capacity of PHI is related to the conductivity of the cation and its binding force for photogenerated electrons.