Fabricating a type II heterojunction by growing lead-free perovskite Cs₂AgBiBr₆in situ on graphite-like g-C₃N₄ nanosheets for enhanced photocatalytic CO₂ reduction

Perovskite-based photocatalysts have received significant attention for converting CO₂ into fuels, such as CO, CH₄ 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-C₃N₄@Cs₂AgBiBr₆ (CABB) type II heterojunction photocatalyst has been prepared by growing lead-free CABB nanocrystals (10-14 nm) on the graphite-like carbon nitride (g-C₃N₄) nanosheet using the in situ crystallization method. The resulting nanocomposite, g-C₃N₄@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 CH₄ under visible light irradiation, the nanocomposite exhibited enhanced photocatalytic efficiency in CO₂ reduction compared to CABB and g-C₃N₄. The improved photocatalytic performance of the g-C₃N₄@CABB nanocomposite was attributed to the fabricated type II heterojunction, which boosted the interfacial charge transfer from g-C₃N₄ to CABB. This work will inspire the design of heterojunction-based photocatalysts and increase the fundamental understanding of perovskite-based catalysts in the CO₂ photoreduction process.