LAUSR

The identity of charge transfer process at the heterogeneous interface plays an important role in improving the stability, activity, and selectivity of heterojunction catalysts. And, in situ irradiation X‐ray photoelectron spectroscopy (XPS) coupled with UV light optical fiber measurement setup is developed to monitor and observe the photoelectron transfer process between heterojunction. However, the in‐depth relationship of binding energy and irradiation light wavelength is missing based on the fact that the incident light is formed by coupling light with different wavelengths. Furthermore, a quantitative understanding of the charge transfer numbers and binding energy remains elusive. Herein, based on the g‐C3N4/SnO2 model catalyst, a wavelength‐dependent Boltzmann function to describe the changes of binding energy and wavelength through utilizing a continuously adjustable monochromatic light irradiation XPS technique is established. Using this method, this study further reveals that the electrons transfer number can be readily calculated forming an asymptotic model. This methodology provides a blueprint for deep understanding of the charge‐transfer rules in heterojunction and facilitates the future development of highly active advanced catalysts.