RESUMO
Dark photocatalysis is the ability of a photocatalyst to accumulate photocarriers during light irradiation and consume them for redox reactions under dark conditions. This phenomenon of photocatalysts storing photocarriers is known as charge accumulation. Dark photocatalysts can mitigate fluctuations in photocatalytic reaction efficiency in response to fluctuating solar irradiation. Potassium poly(heptazine imide) (K-PHI) has attracted considerable attention due to its high photocatalytic efficiency and ability to undergo dark photocatalysis. However, the detailed mechanism of charge accumulation in K-PHI remains unclear because photochromism, potassium ion desorption, and charge accumulation occur simultaneously triggered by light irradiation, limiting the comprehensive understanding of this mechanism. To elucidate the charge accumulation mechanism in K-PHI, highly oriented K-PHI thin films were prepared. Then, their fundamental physical properties and optical response of their electrical properties were investigated. We succeeded in separately observing photochromism, potassium ion desorption, and charge accumulation induced by light irradiation on K-PHI and proposed a comprehensive model to explain these phenomena. This study not only provides insights into the unique physical phenomena exhibited by K-PHI but also contributes to the development of solar energy-storage materials in the future.
RESUMO
Photo-stimuli response in materials is a fascinating feature with many potential applications. A photoresponsive gel of poly(heptazine imide), PHI, termed PHIG, exhibits photochromism, photoconductivity, and photo-induced charge accumulation, and is generated using ionic liquids and PHI. Although there are several examples of ionic liquid gels that exhibit photochromism and photoconductivity, this is the first report of an ionic liquid gel that exhibits both these properties as well as charge accumulation. We conducted experimental and theoretical investigations to understand the mechanism of the photostimulus response of PHIG, especially charge accumulation. The proposed model explains both the mechanism of charge accumulation and dark photocatalysis by PHI and provides new concepts in the field of photofunctional materials.
