Phase‐Engineered MoS 2 Photoelectrodes for Solar Hydrogen Production: Mechanistic Comparison of Semiconducting 2H and Metallic 1T Phases for Enhanced Charge Transfer and Catalytic Efficiency

Phase manipulation of transition metal dichalcogenides is presented as a promising approach for designing and tuning the electronic band structure and catalytic activity for solar‐driven hydrogen production. In this work, phase‐pure with a distinct electronic band semiconducting 2H‐MoS 2 and metallic 1T‐MoS 2 were synthesized through controlled hydrothermal technique. Significantly improved photocurrent density to 4.2 mA cm −2 at 1.0 V, donor density, lower charge‐transfer resistance, and improved incident photon‐to‐current efficiency of ∼30% were achieved for the 1T‐MoS 2 . Faradaic efficiency experiments demonstrated highly efficient hydrogen production ∼95% with stable operation over 4.2 h for 1T‐MoS 2 , while 2H‐MoS 2 showed lower catalytic activity with higher structural stability. These results suggest that enhanced charge‐transfer kinetics, higher carrier concentration, and phase‐associated structural disorder play a more significant role in determining photoelectrochemical(PEC) activity than optical absorption alone. This work provides insight into phase‐dependent catalytic activity of MoS 2 and demonstrates crystal phase engineering as a powerful tool for designing highly efficient photoelectrodes.