Water-stable and hydrophobicity tunable organolead halide materials with Pb-N coordination for electrochemical CO2 reduction

The commercialization of halide perovskite devices is limited by their moisture stability. The lower bonding energy of van der Waals interactions or hydrogen bonding interactions involved in the layered hybrid perovskites cannot fulfill the long-term water stability. To improve their intrinsic water-stability, we introduce coordination interactions between bidentate ligands and metal ions to design water-stable and hydrophobic organo-lead halide crystalline materials APbX(2) (A = Bipyridine; X = Cl, Br, I). The crystalline materials remain completely stable after continuous water treatment for 24 h due to the higher water osmotic energy barrier of APbX(2) crystals induced by the strong Pb-N coordination. The typical hydrophobicity is negatively correlated with the surface adsorption energy of APbX(2), i.e. the lower the surface adsorption energy, the higher the hydrophobicity. Benefiting from the strong Pb-N coordination interactions, APbX(2) materials exhibit good photostability with unchanged morphologies and identical crystallinity. Then such APbX(2) is used for electrochemical CO2 reduction in aqueous solution and the highest faradaic efficiency (FE) of about 60% for the HCOOH product can be achieved. The current work not only provides a general strategy for designing and applying water-stable hybrid perovskites in aqueous media, but also offers a deeper understanding toward the mechanism of water stability and hydrophobicity.