Impact of Electrochemical Doping on the Excited State Decay of 2H-MoSe 2 Nanosheets

Colloidal 2H-MoSe 2 nanosheets combine solution processability with electronic properties attractive for photocatalytic water splitting, yet the electrochemical stability of the excited state remains poorly understood. We combine potential-modulated absorption spectroscopy and complementary electrochemical methods with transient absorption spectroscopy to investigate charge injection and excited-state dynamics in few-layer 2H-MoSe 2 nanosheet films. We determine the electron affinity, ionization potential and exciton binding energy and predict an overpotential of +0.6 V for the photocatalytic hydrogen evolution reaction. Prolonged exposure to electrochemical operating conditions reduces the lifetime of the excited state, which scales with the overpotential, and which is particularly pronounced under anodic conditions. Our work establishes absorption spectroelectrochemistry as a powerful probe of colloidal transition-metal dichalcogenides and identifies solution-processable 2H-MoSe 2 nanosheets as promising photocathode components for S-scheme heterostructures.