Efficient Thin-Film CdS-MoS2-rGO Photocathode Composite for Photoelectrochemical Hydrogen Evolution Reaction at Neutral pH

In this work, a CdS–MoS₂–rGO thin-film photocathode was fabricated on FTO substrates via a single-ink drop–spin-coating method followed by annealing under N₂ atmosphere. Among the studied compositions, the film containing 86:9:5 wt% of CdS, MoS₂, and rGO exhibited the best photoelectrochemical performance. Under visible-light illumination from a 50 W halogen lamp (~0.25 sun) in neutral electrolyte, the optimized photocathode achieved a photocurrent density of 0.83 mA cm⁻² at −0.75 V vs Ag/AgCl and retained approximately 96% of its initial current during 60 min of chopped-light operation. Electrochemical impedance spectroscopy revealed a reduced charge-transfer resistance (~120 Ω·cm²), while the Tafel slope decreased to ~85 mV dec⁻¹, indicating enhanced charge transfer and hydrogen evolution kinetics. Hydrogen production was confirmed by gas chromatography, with an evolution rate of ~58.6 μmol h⁻¹. The improved performance is attributed to the synergistic roles of CdS as the light absorber, rGO as an electron-transport network, and MoS₂ as a cocatalyst. These results demonstrate the potential of the CdS–MoS₂–rGO architecture for photoelectrochemical hydrogen evolution under neutral conditions.