Field-enhanced photocarrier separation in a split-gate MOS photocatalytic device

Semiconductor photocatalysis offers significant potential for solving energy and environment challenges, but its efficiency is often limited by the rapid recombination of photogenerated charge carriers. In this study, we present a photocatalytic device based on a metal–oxide–semiconductor architecture, featuring an asymmetric split-gate design that generates an alternately distributed lateral electrostatic field across the semiconductor photocatalytic film. BiVO4 is selected as the photosensitive material due to its excellent visible-light absorption and chemical stability, while HfO2 serves as a high-k dielectric layer to electrically isolate the gate electrodes from the photocatalytic film. The cross-arrayed asymmetric gates enable spatial modulation of local work functions, allowing independent control over electron and hole transport pathways within the plane of the photocatalytic film. This in-plane separation of photocarriers is different from conventional vertical separation. It effectively suppresses photocarrier recombination, prolongs photocarrier lifetimes, and enhances photocatalytic performance. Photocatalytic degradation experiments show performance improvements of 9.17% for Rhodamine B and 23.84% for chlortetracycline under optimal gate bias. This work demonstrates an approach to field-effect engineering for in-plane photocarrier modulation, offering precise and efficient control over semiconductor photocatalytic processes.