Novel Catalyst Converts CO2 to CO with High Selectivity

A research team led by Jie Chen from Xi’an Jiaotong University has developed a new visible-light-driven (λ > 420 nm) Z-scheme heterojunction photocatalyst for photocatalytic CO₂ reduction. The catalyst integrates 0D Cs₃Bi₂I₉ nanoparticles with 1D WO₃ nanorods, synthesized using an in situ growth method. The catalyst was extensively tested and analyzed to evaluate its performance and the underlying mechanisms.

Creating sustainable energy conversion and CO₂ utilization technologies is crucial due to the growing global energy demand and environmental concerns. Photocatalytic CO₂ reduction, which uses solar energy to convert CO₂ into valuable molecules, is one potential solution. However, current photocatalysts face challenges such as low light absorption, poor charge separation, and high energy barriers for CO₂ reduction.

Metal halide perovskites (ABX₃) have shown promise in photocatalysis due to their superior light absorption and charge transport capabilities. However, lead-containing perovskites suffer from issues like toxicity and instability, prompting researchers to explore lead-free alternatives, such as bismuth (Bi)-based materials.

Among these alternatives, the lead-free halide perovskite Cs₃Bi₂I₉ has attracted attention for its excellent optoelectronic performance, though it is limited by aggregation and insufficient oxidation ability.

The photocatalytic CO₂ reduction performance of the 0D/1D Cs₃Bi₂I₉/WO₃ Z-scheme heterojunction was outstanding. Important conclusions include:

• Enhanced CO₂ Reduction Activity: The catalyst showed a CO selectivity of 98.7 % and a CO production rate of 16.5 μmol/(g·h), which is roughly three times greater than that of pure Cs₃Bi₂I₉ (5.3 μmol/(g·h)).
• Stability: After three rounds of three-hour reactions, the catalyst's performance remained steady, and no appreciable structural alterations were noticed.
• Charge Transfer Mechanism: Under light irradiation, electrons move from WO₃ to Cs₃Bi₂I₉ via a Z-scheme charge transfer pathway, which reduces recombination and facilitates effective charge separation, according to in situ XPS and ESR observations.
• Photophysical and Photoelectrochemical Properties: Time-resolved photoluminescence studies, electrochemical impedance spectroscopy, and surface photovoltaic spectroscopy all demonstrated the heterojunction's effective charge carrier separation and transfer.

This work advances the design of effective heterojunctions for photocatalytic CO₂ reduction. By enhancing the performance of lead-free halide perovskites, the successful development of the 0D/1D Z-scheme heterojunction offers a promising strategy for creating advanced photocatalysts.

The study paves the way for more efficient and stable photocatalytic materials by combining morphological engineering with the Z-scheme heterojunction design, supporting initiatives to reduce carbon emissions and develop sustainable energy solutions.

Journal Reference:

Ding, Y., et al. (2025) In situ construction of Cs₃Bi₂I₉/WO₃ 0D/1D Z-scheme heterojunction photocatalyst for photochemical CO₂ reduction under visible light. Frontiers in Energy. doi.org/10.1007/s11708-025-0989-1.