In-situ growth of PbI2 on ligand-free FAPbBr3 nanocrystals to significantly ameliorate the stability of CO2 photoreduction

Excellent optical properties involving strong visible light response and superior carrier transport endow metal halide perovskites(MHP)with a fascinating prospect in the field of photocatalysis.Nevertheless,the poor stability of MHP nanocrystals(NCs)in water-contained system,especially without the protection of long alkyl chain ligands,severely restricts their photocatalytic performance.In this context,we report an effortless strategy for the generation of ligand-free MHP NCs based photocatalyst with high water toler-ance,by coating PbI2 on the surface of ligand-free formamidinium lead bromide(FAPbBr3)NCs via the facile procedure of in-situ conversion with the aid of ZnI2.Under the protection of PbI2 layer,the resultant FAPbBr3/PbI2 composite exhibits significantly ameliorated stability in an artificial photosynthesis system with CO2 and H2O vapor as feedstocks.Moreover,the formation of compact PbI2 layer can accelerate the separation of photogenerated carriers in FAPbBr3 NCs,bringing forth a remarkable improvement of CO2 photoreduction efficiency with an impressive electron consumption yield of 2053 μmol/g in the absence of organic sacrificial agents,which is 7-fold over that of pristine FAPbBr3 NCs.