Fabricating a type II heterojunction by growing lead-free perovskite Cs 2 AgBiBr 6 in situ on graphite-like g-C 3 N 4 nanosheets for enhanced photocatalytic CO 2 reduction.

Perovskite-based photocatalysts have received significant attention for converting CO 2 into fuels, such as CO, CH 4 or long alkyl chains. However, the use of these catalysts is plagued by several limitations, such as poor stability, lead toxicity, and inadequate conversion efficiency due to the rapid recombination of carriers. Herein, a g-C 3 N 4 @Cs 2 AgBiBr 6 (CABB) type II heterojunction photocatalyst has been prepared by growing lead-free CABB nanocrystals (10-14 nm) on the graphite-like carbon nitride (g-C 3 N 4 ) nanosheet using the in situ crystallization method. The resulting nanocomposite, g-C 3 N 4 @CABB, demonstrated an efficient charge transfer pathway via a typical type II heterojunction. With formation rates of 10.30 μmol g -1 h -1 for CO and 0.88 μmol g -1 h -1 for CH 4 under visible light irradiation, the nanocomposite exhibited enhanced photocatalytic efficiency in CO 2 reduction compared to CABB and g-C 3 N 4 . The improved photocatalytic performance of the g-C 3 N 4 @CABB nanocomposite was attributed to the fabricated type II heterojunction, which boosted the interfacial charge transfer from g-C 3 N 4 to CABB. This work will inspire the design of heterojunction-based photocatalysts and increase the fundamental understanding of perovskite-based catalysts in the CO 2 photoreduction process.