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.
DOI: 10.1007/s11708-025-0989-1