Cs(3)Bi(2)Br(9)/g-C(3)N(4) Direct Z-Scheme Heterojunction for Enhanced Photocatalytic Reduction of CO(2) to CO

[Image: see text] Lead-free halide perovskite derivative Cs(3)Bi(2)Br(9) has recently been found to possess optoelectronic properties suitable for photocatalytic CO(2) reduction reactions to CO. However, further work needs to be performed to boost charge separation for improving the overall efficiency of the photocatalyst. This report demonstrates the synthesis of a hybrid inorganic/organic heterojunction between Cs(3)Bi(2)Br(9) and g-C(3)N(4) at different ratios, achieved by growing Cs(3)Bi(2)Br(9) crystals on the surface of g-C(3)N(4) using a straightforward antisolvent crystallization method. The synthesized powders showed enhanced gas-phase photocatalytic CO(2) reduction in the absence of hole scavengers of 14.22 (±1.24) μmol CO g(–1) h(–1) with 40 wt % Cs(3)Bi(2)Br(9) compared with 1.89 (±0.72) and 5.58 (±0.14) μmol CO g(–1) h(–1) for pure g-C(3)N(4) and Cs(3)Bi(2)Br(9), respectively. Photoelectrochemical measurements also showed enhanced photocurrent in the 40 wt % Cs(3)Bi(2)Br(9) composite, demonstrating enhanced charge separation. In addition, stability tests demonstrated structural stability upon the formation of a heterojunction, even after 15 h of illumination. Band structure alignment and selective metal deposition studies indicated the formation of a direct Z-scheme heterojunction between the two semiconductors, which boosted charge separation. These findings support the potential of hybrid organic/inorganic g-C(3)N(4)/Cs(3)Bi(2)Br(9) Z-scheme photocatalyst for enhanced CO(2) photocatalytic activity and improved stability.