Anderson-Type Polyoxometalate-Assisted Synthesis of Defect-Rich Doped 1T/2H-MoSe₂ Nanosheets for Efficient Seawater Splitting and Mg/Seawater Batteries

Designing high-performance hydrogen evolution reaction (HER) catalysts is crucial for seawater splitting. Herein, we demonstrate a facile Anderson-type polyoxometalate-assisted synthesis route to prepare defect-rich doped 1T/2H-MoSe2 nanosheets. As demonstrated, the optimized defect-rich doped 1T/2H-MoSe2 nanosheets display low overpotentials of 116 and 274 mV to gain 10 mA cm–2 in acidic and simulated seawater for the HER, respectively. A magnesium (Mg)/seawater battery was fabricated with the defect-rich doped 1T/2H-MoSe2 nanosheet cathode, displaying the highest power density of up to 7.69 mW cm–2 and stable galvanostatic discharging over 24 h. The theoretical and experimental investigations show that the superior HER and battery performances of the heteroatom-doped MoSe2 nanosheets are attributed to both the improved intrinsic catalytic activity (effective activation of water and favorable subsequent hydrogen desorption) and the abundant active sites, benefiting from the favorable catalytic factors of the doped heteroatom, 1T phase, and defects. Our work presents an intriguing structural modulation strategy to design high-performance catalysts toward both HER and Mg/seawater batteries.