In situ construction of Cs3Bi2I9/WO3 0D/1D Z-scheme heterojunction photocatalyst for photochemical CO2 reduction under visible light

In the face of growing global energy demands and environmental concerns, developing sustainable technologies for energy conversion and carbon dioxide (CO₂) utilization is crucial. Photocatalytic CO₂ reduction, which leverages solar energy to convert CO₂ into valuable chemicals, stands out as a promising solution. However, existing photocatalysts face challenges such as insufficient light absorption, poor charge separation, and high energy barriers for CO₂ reduction.

Metal halide perovskites (ABX₃) have shown potential in photocatalysis due to their excellent light absorption and charge transport properties. Lead-containing perovskites, however, face issues like degradation and toxicity, prompting researchers to explore lead-free alternatives like bismuth (Bi)-based materials. Cs₃Bi₂I₉, a lead-free halide perovskite, has attracted attention for its high optoelectronic performance but is limited by aggregation and insufficient oxidation ability.

A research team led by Jie Chen from Xi’an Jiaotong University has developed a novel visible-light-driven (λ > 420 nm) Z-scheme heterojunction photocatalyst composed of 0D Cs₃Bi₂I₉ nanoparticles on 1D WO₃ nanorods for photocatalytic CO₂ reduction. The catalyst was synthesized using an in situ growth approach, where Cs₃Bi₂I₉ nanoparticles were grown on WO₃ nanorods. The research team conducted extensive experiments and characterizations to evaluate the catalyst's performance and understand its underlying mechanisms.

The 0D/1D Cs₃Bi₂I₉/WO₃ Z-scheme heterojunction demonstrated remarkable photocatalytic CO₂ reduction performance. Key findings include:

1. Enhanced CO₂ Reduction Activity: The catalyst achieved a CO production rate of 16.5 μmol/(g·h), approximately three times higher than that of pristine Cs₃Bi₂I₉ (5.3 μmol/(g·h)), with a CO selectivity of 98.7%.
2. Stability: The catalyst maintained stable performance after three cycles of 3-hour reactions, with no significant structural changes observed.
3. Charge Transfer Mechanism: In situ XPS and ESR measurements revealed a Z-scheme charge transfer pathway, where electrons transfer from WO₃ to Cs₃Bi₂I₉ under light illumination, facilitating efficient charge separation and reducing recombination.
4. Photophysical and Photoelectrochemical Properties: The heterojunction exhibited efficient charge carrier transfer and separation, as evidenced by surface photovoltage spectroscopy, electrochemical impedance spectroscopy, and time-resolved photoluminescence measurements.

This work provides valuable insights into the design of efficient heterojunctions for photocatalytic CO₂ reduction. The successful construction of the 0D/1D Z-scheme heterojunction not only enhances the performance of lead-free halide perovskites but also offers a promising strategy for developing advanced photocatalysts. By combining morphological engineering with the Z-scheme heterojunction design, this study paves the way for more efficient and stable photocatalytic materials, contributing to sustainable energy solutions and carbon emission reduction efforts.