Dimensional reduction and edge-state engineering unlock superior photocatalytic hydrogen evolution in lead-free (C6H5–C2H4–NH3)4AgBiBr8 layered double perovskite

Lead-free halide perovskites offer a less toxic route to visible-light photocatalytic hydrogen production. Here, two-dimensional (PEA) 4 AgBiBr 8 double perovskite nanoparticles (∼12 nm) were synthesized by ligand-assisted reprecipitation (LARP). Compared with the bulk counterpart, the nanoparticles show stronger visible-light absorption and more efficient separation of photogenerated charge carriers. In aqueous HBr under visible light (λ ≥ 420 nm), they deliver a cocatalyst-free H 2 evolution rate of 854.7 μmol g −1 h −1 , about tenfold that of bulk (PEA) 4 AgBiBr 8 . Post-reaction X-ray photoelectron spectroscopy shows no metallic Ag formation, excluding photoreduction of lattice Ag + and an in situ Ag cocatalyst. Impedance spectroscopy under illumination reveals reduced charge-transfer resistance. The enhanced activity is attributed to efficient charge separation, reactive edge sites and favourable band alignment. These results establish morphology control as an effective strategy for designing lead-free perovskite photocatalysts for solar hydrogen production.