Locally‐doped MoS ₂ monolayer with in‐plane bifunctional heterostructure toward overall water splitting

Abstract Exploring earth‐abundant, highly active bifunctional electrocatalysts for efficient hydrogen and oxygen evolution is crucial for water splitting. However, due to their distinct free energies and conducting behaviors (electron/hole), balancing the catalytic efficiency between hydrogen and oxygen evolution remains challenging for achieving bifunctional electrocatalysts. Here, we report a locally‐doped MoS 2 monolayer with an in‐plane heterostructure acting as a bifunctional electrocatalyst and apply it to the overall water splitting. In this heterostructure, the core region contains Mo/S vacancies, while the ring region was doped by Fe atoms (in two substitution configurations: 1Fe Mo and 3Fe Mo ‐V S clusters) with a p‐type conductive characteristic. Our micro‐cell measurements, combined with density functional theory (DFT) calculations, reveal that the vacancies‐rich core region presents remarkable hydrogen evolution reaction (HER) activity while the Fe‐doped ring gives an excellent oxygen evolution reaction (OER) activity, thus forming an in‐plane bifunctional electrocatalyst. Finally, as a proof‐of‐concept for overall water splitting, we constructed a full‐cell configuration based on a locally‐doped MoS 2 monolayer, which achieved a cell voltage of 1.87 V at 10 mA·cm −2 , demonstrating outstanding performance in strong acid electrolytes. Our work provides insight into the hetero‐integration of bifunctional electrocatalysts at the atomic level, paving the way for designing transition metal dichalcogenide catalysts with activity‐manipulated regions capable of multiple reactions.