Eco‐Friendly Aqueous Electrophoretic Deposition of TiO 2– AgBiS 2 Heterojunctions for Photoelectrochemical Hydrogen Production

Photoelectrochemical (PEC) hydrogen production requires photoanodes that are efficient, stable, and environmentally benign. Although conventional metal oxide photoanodes such as TiO 2 have been extensively studied, their light absorption is confined mainly to the ultraviolet region. AgBiS 2 nanocrystals have emerged as a promising alternative due to their low toxicity and broad visible‐to‐near‐infrared absorption. However, their narrow bandgap leads to severe charge recombination, thereby limiting photocurrent generation. Here, we report a TiO 2 –AgBiS 2 heterostructure photoanode fabricated by an aqueous electrophoretic deposition method (EPD). By functionalizing AgBiS 2 nanocrystals(NCs) with 3‐mercaptopropionic acid(3‐MPA), the particles become hydrophilic, enabling low‐voltage, solvent‐free deposition without toxic organic solvents. The heterostructure combines the efficient charge transport of TiO 2 with the strong light‐harvesting capability of AgBiS 2 , promoting charge separation and suppressing nonradiative recombination. Under AM 1.5G one‐sun illumination, the TiO 2 –AgBiS 2 photoanode delivers a photocurrent density of 3.0 mA cm −2 at 0.6 V vs. RHE, with improved stability and performance compared with conventional oleic acid‐capped AgBiS 2 prepared by high‐voltage methods. These results demonstrate a viable and sustainable strategy for heterojunction‐based photoelectrodes for solar hydrogen production.