A halide perovskite based ternary heterojunction with multi-shell hollow structure for stable and efficient artificial photosynthesis

Low-cost halide perovskite materials hold great promise as photocatalysts for CO2 reduction. However, their inferior water-tolerance will lead to a substantial decline in activity during prolonged photocatalytic CO2 reduction with water as the electron source. Herein, we integrate a lead-free halide perovskite Cs3Bi2I9 as photoactive layer with TiO2 as water oxidation catalyst and g-C3N4 as CO2 reduction catalyst to construct a ternary heterojunction (TiO2/Cs3Bi2I9/g-C3N4) with a multi-shell hollow structure. The formation of heterojunction endows TiO2/Cs3Bi2I9/g-C3N4 composite with enhanced photocatalytic activity for CO2 reduction due to the improved photogenerated carrier separation. TiO2/Cs3Bi2I9/g-C3N4 achieves a CO yield of 120.6 μmol g−1 h−1 for photocatalytic CO2 reduction, which is 3.1 times higher than that of individual Cs3Bi2I9. More importantly, benefitting from the double-sided protection of g-C3N4 and TiO2, the photocatalytic CO2 reduction activity of TiO2/Cs3Bi2I9/g-C3N4 remains undiminished even over 100 h of continuous light irradiation, demonstrating significantly improved stability in water-contained reaction system.