Photoelectrochemical performance of MoS 2 -modified TiO 2 photoanodes: interplay between charge separation and interfacial charge transfer

Abstract Herein, MoS 2 –TiO 2 composite photoanodes with MoS 2 contents ranging from 0 to 20 wt% were systematically investigated to elucidate the interplay between bulk charge transport and interfacial charge-transfer processes. The incorporation of MoS 2 extends light absorption into the visible region and suppresses radiative recombination, thereby improving charge-carrier utilization. The optimized sample (15 wt% MoS 2 ) exhibits an applied bias photon-to-current efficiency (ABPE) of 0.031%, compared to 0.024% for pristine TiO 2 under identical conditions. Electrochemical impedance spectroscopy combined with distribution of relaxation times (DRT) analysis reveals that MoS 2 incorporation predominantly reduces the mid-frequency resistance associated with bulk charge transport, whereas TiO 2 -rich compositions retain relatively lower interfacial charge-transfer resistance. This competition leads to a non-monotonic and bias-dependent PEC response, in which moderate MoS 2 loading favors performance at low bias, while higher MoS 2 content enhances photocurrent at elevated potentials. These findings provide mechanistic insight into the balance between transport and interfacial processes in oxide–chalcogenide composite photoanodes.