Composite of CH3NH3PbI3 with Reduced Graphene Oxide as a Highly Efficient and Stable Visible‐Light Photocatalyst for Hydrogen Evolution in Aqueous HI Solution

A facile and efficient photoreduction method is employed to synthesize the composite of methylammonium lead iodide perovskite (MAPbI₃ ) with reduced graphene oxide (rGO). This MAPbI₃ /rGO composite is shown to be an outstanding visible-light photocatalyst for H₂ evolution in aqueous HI solution saturated with MAPbI₃ . Powder samples of MAPbI₃ /rGO (100 mg) show a H₂ evolution rate of 93.9 µmol h^-1 , which is 67 times faster than that of pristine MAPbI₃ , under 120 mW cm^-2 visible-light (λ ≥ 420 nm) illumination, and the composite is highly stable showing no significant decrease in the catalytic activity after 200 h (i.e., 20 cycles) of repeated H₂ evolution experiments. The electrochemiluminescence performance of MAPbI₃ is investigated to explore the charge transfer process, to find that the photogenerated electrons in MAPbI₃ are transferred to the rGO sites, where protons are reduced to H₂ .