A g-C 3 N 4 /rGO/Cs 3 Bi 2 Br 9 mediated Z-scheme heterojunction for enhanced photocatalytic CO 2 reduction.

Photocatalytic CO 2 reduction plays a crucial role in advancing solar fuels, and enhancing the efficiency of the chosen photocatalysts is essential for sustainable energy production. This study demonstrates advancements in the performance of g-C 3 N 4 as a photocatalyst achieved through surface modifications such as exfoliation to increase surface area and surface oxidation for improved charge separation. We also introduce reduced graphene oxide (rGO) in various ratios to both bulk and exfoliated g-C 3 N 4 , which effectively mitigates charge recombination and establishes an optimal ratio for enhanced efficiency. g-C 3 N 4 /rGO serves to fabricate a hybrid organic/inorganic heterojunction with Cs 3 Bi 2 Br 9 , resulting in a g-C 3 N 4 /rGO/Cs 3 Bi 2 Br 9 composite. This leads to a remarkable increase in photocatalytic conversion of CO 2 and H 2 O to CO, H 2 and CH 4 at rates of 54.3 (±2.0) μmol e - g -1 h -1 , surpassing that of pure Cs 3 Bi 2 Br 9 (11.2 ± 0.4 μmol e - g -1 h -1 ) and bulk g-C 3 N 4 (5.5 ± 0.5 μmol e - g -1 h -1 ). The experimentally determined energy diagram indicates that rGO acts as a solid redox mediator between g-C 3 N 4 and Cs 3 Bi 2 Br 9 in a Z-scheme heterojunction configuration, ensuring that the semiconductor (Cs 3 Bi 2 Br 9 ) with the shallowest conduction band drives the reduction and the one with the deepest valence band (g-C 3 N 4 ) drives the oxidation. The successful formation of this high-performance heterojunction underscores the potential of the developed composite as a photocatalyst for CO 2 reduction, offering promising prospects for advancing the field of solar fuels and achieving sustainable energy goals.