Efficient Z-Scheme Configuration for Photocatalytic CO2 Reduction through g-C3N4 and Cs3Bi2Br9 Heterojunctions Enhanced by Reduced Graphene Oxide

Photocatalytic CO₂ reduction is pivotal for progressing solar fuel technologies, demanding catalysts with enhanced efficiency. Combining the optoelectronic characteristics of Cs₃Bi₂Br₉ and the versatility of g-C₃N₄, this study aims to create a synergistic platform for photocatalysis, harnessing the unique strengths of each semiconductor to enhance overall performance in applications such as solar fuel generation and photocatalytic CO₂ reduction.
Building on our previous studies where the ratio of g-C₃N₄ to Cs₃Bi₂Br₉ was optimized for high CO₂ conversion to CO, this study presents a dual-modification approach to amplify the performance of g-C₃N₄ as a photocatalyst.1 Surface modifications, including exfoliation for increased surface area and surface oxidation for improved charge separation, were employed on g-C₃N₄. The introduction of reduced graphene oxide (rGO) at various ratios, integrated into both bulk and exfoliated g-C₃N₄, effectively mitigated charge recombination. An optimal rGO/g-C₃N₄ ratio was identified, showcasing superior efficiency.
Importantly, the study also introduces a hybrid inorganic/organic heterojunction by combining the optimized rGO/g-C₃N₄ with Cs₃Bi₂Br₉ into a Cs₃Bi₂Br₉/rGO/g-C₃N₄ Z-scheme composite. This synergistic integration resulted in a remarkable increase in photocatalytic activity, reaching 54.3 (± 2.0) µmol g^-1 e^- h^-1 on an electron basis for CO, H₂, and CH₄ production, surpassing pure Cs₃Bi₂Br₉ (11.2 ± 0.4 µmol g^-1 e^- h^-1) and bulk g-C₃N₄ (5.5 ± 0.5 µmol g^-1 e^- h^-1).
A comprehensive characterization shows the charge transfer mechanism within the composite to take place via the rGO, acting as a solid redox mediator, in a Z-scheme heterojunction where Cs₃Bi₂Br₉ drives the reduction and g-C₃N₄ the oxidation, explaining its enhanced photocatalytic activity. The successful formation of this high-performance heterojunction underscores the composite's potential as an efficient photocatalyst for CO₂ reduction, promising substantial advancements in solar fuel technologies and aligning with sustainable energy goals.
¹ Cs₃Bi₂Br₉/g-C₃N₄ Direct Z-Scheme Heterojunction for Enhanced Photocatalytic Reduction of CO₂ to CO
Yasmine Baghdadi, Filipp Temerov, Junyi Cui, Matyas Daboczi, Eduardo Rattner, Michael Segundo Sena, Ioanna Itskou, and Salvador Eslava
Chemistry of Materials 2023 35 (20), 8607-8620
DOI: 10.1021/acs.chemmater.3c01635