Highly Efficient Electrocatalyst of 2D–2D gC3N4–MoS2 Composites for Enhanced Overall Water Electrolysis

For future clean and renewable energy technology, designing highly efficient and robust electrocatalysts is of great importance. Particularly, creating efficient bifunctional electrocatalysts capable of effectively catalyzing both hydrogen- and oxygen-evolution reactions (HERs and OERs) is vital for overall water electrolysis. In this study, we employ 2D molybdenum disulfide (MoS₂) nanosheets and pyrolytically fabricated 2D graphitic carbon nitride (gC₃N₄) nanosheets to create 2D gC₃N₄-decorated 2D MoS₂ (2D-2D gC₃N₄-MoS₂) nanocomposites using a facile sonochemical method. The 2D-2D gC₃N₄-MoS₂ nanocomposites show an interconnected and agglomerated structure of 2D gC₃N₄ nanosheets decorated on 2D MoS₂ nanosheets. For water electrolysis, the gC₃N₄-MoS₂ nanocomposites exhibit low overpotentials (OER: 225 mV, HER: 156 mV), small Tafel slope values (OER: 49 mV/dec, HER: 101 mV/dec), and excellent durability (up to 100 h for both OER and HER) at 10 mA/cm² in 1 M KOH. Furthermore, the gC₃N₄-MoS₂ nanocomposites show excellent overall water electrolysis performance with a low full-cell voltage (1.52 V at 10 mA/cm²) and outstanding long-term cell stability. The superb bifunctional activities of the gC₃N₄-MoS₂ nanocomposites are attributed to the synergistic effects of 2D gC₃N₄ (i.e., low charge-transfer resistance) and 2D MoS₂ (i.e., a large electrochemically active surface area). These findings suggest that the 2D-2D gC₃N₄-MoS₂ nanocomposites could serve as excellent bifunctional catalysts for overall water electrolysis.