Stable and Highly Efficient Photocatalysis with Lead‐Free Double‐Perovskite of Cs2AgBiBr6

Abstract Composition engineering of halide perovskite allows the tunability of the band gap over a wide range so that photons can be effectively harvested, an aspect that is of critical importance for increasing the efficiency of photocatalysis under sunlight. However, the poor stability and the low photocatalytic activity of halide perovskites prevent use of these defect‐tolerant materials in wide applications involving photocatalysis. Here, an alcohol‐based photocatalytic system for dye degradation demonstrated high stability through the use of double perovskite of Cs 2 AgBiBr 6 . The reaction rate on Cs 2 AgBiBr 6 is comparable to that on CdS, a model inorganic semiconductor photocatalyst. The fact of fast reaction between free radicals and dye molecules indicates the unique catalytic properties of the Cs 2 AgBiBr 6 surface. Deposition of metal clusters onto Cs 2 AgBiBr 6 effectively enhances the photocatalytic activity. Although the stability (five consecutive photocatalytic cycles without obvious decrease of efficiency) requires further improvements, the results indicate the significant potential of Cs 2 AgBiBr 6 ‐based photocatalysis.