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 .