This study reports the synthesis of cadmium sulfide (CdS) nanoparticles on Li+-inserted TiO2 nanotube array (Li-TNA) to fabricate Li-TNA/CdS heterojunction electrodes for photoelectrochemical (PEC) hydrogen production under air mass (AM) 1.5 light and solar visible light (lambda > 420 nm). For fabrication of the heterojunction, Li+ is rapidly inserted into TNA pre-grown on Ti foil, and CdS is then photodeposited onto the Li-TNA electrodes for varying deposition times. Surface analyses reveal that sub-100-nm polycrystalline CdS particles partly cover the Li-TNA (length: similar to 800 nm, pore diameter: similar to 100 nm), enabling the heterojunction to utilize AM 1.5 light as well as visible light. In aqueous solutions of sulfide and sulfite, the Li-TNA/CdS exhibits an incident photon-to-current efficiency (IPCE) of similar to 20% (lambda = 420 nm) while generating H-2 at a Faradaic efficiency of similar to 100%. This PEC performance is superior to that of TNA/CdS, which is attributed to the Li+-enhanced charge transfer at the TNA/CdS interface. Electrochemical impedance analysis shows that the charge-transfer resistance of the TNA is reduced by similar to 60% by Li+ insertion. Time-resolved photoluminescence decay profiles further reveal that the charge transfer in Li-TNA is completed within 0.8 ns, which is similar to 33% faster than that in TNA. The sample surface is analyzed using scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and ultraviolet-visible spectroscopy, and the PEC behavior of the samples is discussed in detail.