A g-CN/rGO/CsBiBr mediated Z-scheme heterojunction for enhanced photocatalytic CO reduction.

Photocatalytic CO 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-CN 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-CN, which effectively mitigates charge recombination and establishes an optimal ratio for enhanced efficiency. g-CN/rGO serves to fabricate a hybrid organic/inorganic heterojunction with CsBiBr, resulting in a g-CN/rGO/CsBiBr composite. This leads to a remarkable increase in photocatalytic conversion of CO and HO to CO, H and CH at rates of 54.3 (±2.0) μmol g h, surpassing that of pure CsBiBr (11.2 ± 0.4 μmol g h) and bulk g-CN (5.5 ± 0.5 μmol g h). The experimentally determined energy diagram indicates that rGO acts as a solid redox mediator between g-CN and CsBiBr in a Z-scheme heterojunction configuration, ensuring that the semiconductor (CsBiBr) with the shallowest conduction band drives the reduction and the one with the deepest valence band (g-CN) drives the oxidation. The successful formation of this high-performance heterojunction underscores the potential of the developed composite as a photocatalyst for CO reduction, offering promising prospects for advancing the field of solar fuels and achieving sustainable energy goals.