Hierarchical Hybrids Made of Mixed Metal-Based Sillén-Structured Cd_<i>x</i>BiO₂Br @ Graphene Oxide for Efficient Photocatalytic H₂O₂ Production

In this article, multilayered Sillén-structured mixed metallic CdxBiO2Br has been synthesized through hydrothermal methods. Detailed structure–property correlations suggest that replacement of Bi3+ cations by Cd2+ transforms the conduction band position suitable for the desired oxygen reduction reaction. It is further correlated by density functional theory calculations. Finally, unique flower-like hierarchical hybrid heterostructures have been fabricated by growing this multilayered CdxBiO2Br on graphene oxide (GO) nanosheets. Here, GO nanosheets play dual roles, i.e., (i) GO acts as the template to grow these typical hybrid heterostructures with improved surface-active sites and oxygen vacancies and (ii) second, the GO sheet further improves the photoinduced charge separation processes with respect to bare CdxBiO2Br and BiOBr. All the as-synthesized materials have been utilized for photocatalytic H2O2 productions, and maximum production efficiency has been observed (∼13 mM gcatalyst–1) for the optimized hierarchical hybrids of CdxBiO2Br and GO nanosheets. The overall trends in H2O2 production efficiencies have been further supported by detailed transient photocurrent response studies and electrochemical impedance spectroscopy. Finally, molecular insights into the overall photocatalytic mechanism have been unveiled by scavenging the free radicals and the respective reaction intermediates.