Eco-Friendly Aqueous Electrophoretic Deposition of TiO2-AgBiS2 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 TiO2 have been extensively studied, their light absorption is confined mainly to the ultraviolet region. AgBiS2 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 TiO2-AgBiS2 heterostructure photoanode fabricated by an aqueous electrophoretic deposition method (EPD). By functionalizing AgBiS2 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 TiO2 with the strong light-harvesting capability of AgBiS2, promoting charge separation and suppressing nonradiative recombination. Under AM 1.5G one-sun illumination, the TiO2-AgBiS2 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 AgBiS2 prepared by high-voltage methods. These results demonstrate a viable and sustainable strategy for heterojunction-based photoelectrodes for solar hydrogen production.