Locally-doped MoS2 monolayer with in-plane bifunctional heterostructure toward overall water splitting

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 MoS₂ 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 MoS₂ 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.

Graphical abstract