1：Experimental Design and Method Selection:

The study employs atomic layer deposition (ALD) to synthesize MoS2 and TiO2 overlayers on CdS/CGSe photocathodes, aiming for low-temperature processing (<200°C) to protect and catalyze the electrodes for hydrogen evolution reaction (HER) in acidic conditions. Methods include coevaporation for CGSe, chemical bath deposition for CdS, ALD for TiO2 and MoOx (converted to MoS2), and tube furnace annealing.

2：Sample Selection and Data Sources:

Samples are fabricated on fluorine-doped tin oxide (FTO) substrates. CGSe films are deposited via a three-stage coevaporation process, with thickness monitored by electron impact emission spectrometry. CdS is deposited by chemical bath deposition. Spectroscopic and electrochemical data are collected from these samples.

3：List of Experimental Equipment and Materials:

Equipment includes ALD reactors (Cambridge Nanotech Savannah and Fiji), tube furnace, spectroscopic ellipsometer, XPS/XAES setup (VG ESCALab MkII with SPECS components), SEM (FEI Magellan 400 XHR), UV-vis-NIR spectrophotometer (Varian Cary 6000i), X-ray diffractometer (Philips PANalytical X'Pert Pro), potentiostat (Bio-Logic VSP), and monochromator (Newport Oriel 74100). Materials include FTO substrates, precursors for ALD (TDMA-Ti, Mo(CO)6, H2S/H2 gas), cadmium sulfate, thiourea, ammonium hydroxide, and various chemicals for deposition and testing.

4：0). Materials include FTO substrates, precursors for ALD (TDMA-Ti, Mo(CO)6, H2S/H2 gas), cadmium sulfate, thiourea, ammonium hydroxide, and various chemicals for deposition and testing. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Steps involve cleaning FTO substrates, depositing CGSe by coevaporation, depositing CdS by chemical bath deposition, depositing TiO2 and MoOx by ALD, converting MoOx to MoS2 in H2S/H2 atmosphere, performing spectroscopic characterizations (XPS, XAES, XES, SEM, etc.), and conducting photoelectrochemical tests (LSV, CA, IPCE) in a three-electrode cell with H2-sparged 0.5 M H2SO4 electrolyte.

5：5 M H2SO4 electrolyte. Data Analysis Methods:

5. Data Analysis Methods: Data analysis includes linear extrapolation for onset potential determination, spectroscopic peak fitting for chemical environment identification, and use of software like ImageJ for area measurement. Statistical methods are not explicitly detailed, but standard calibration and comparison techniques are employed.