Switching Type‐II to S‐scheme Charge Transfer Through Fermi Level Modulation

Directly switching the type of electron transfer from Type‐II to S‐scheme at the heterojunction interfaces of a two‐component photocatalyst is crucial for improving charge separation efficiency in semiconductor‐based photocatalysis technology. A major challenge lies in the effective control of the interfacial band‐edge position or electronic properties of a two‐component photocatalyst. Here, we constructed a “directional valve” in a Zn x Cd 2‐x S 2 –crystalline carbon nitride (Zn x Cd 2‐x S 2 –CN) heterojunction through Fermi level modulation to selectively switch Type‐II to S‐scheme charge transfer. Experimental validation using advanced scanning probe microscopy and in situ photoemission directly observed the switched electron transfer dynamics. The metal probe‐assisted in situ X‐ray photoelectron spectroscopy (XPS) directly demonstrates the electron transition from Type‐II to S‐scheme pathways at the interface, corroborated by illumination‐induced surface potential shifts. Furthermore, the S‐scheme charge transfer in Zn x Cd 2‐x S 2 –CN heterojunction contributed to a four times higher CO 2 photoreduction activity than the Type‐II one. This study provides a new paradigm for rationally controlling interfacial charge dynamics through band engineering.