Atmosphere engineering of metal-free Te/C₃N₄ p-n heterojunction for nearly 100% photocatalytic conversion of CO₂ to CO

Solar-driven carbon dioxide (CO₂) reduction has emerged as a key approach for transforming CO₂ into valuable chemicals and fuels, potentially addressing global environmental and climate challenges. Among the various photocatalysts investigated for this purpose, graphitic carbon nitride (CN) has gained attention as a metal-free n-type organic semiconductor. However, limitations such as inefficient separation of photogenerated carriers and relatively low surface area have hindered the full potential of CN in CO₂ photoreduction.

Recently, interest in CN-based heterojunctions has been further driven by the goal of improving carrier separation and enhancing photocatalytic efficiency. Among the various heterojunction architectures explored, the CN-based p-n heterojunction stands out due to its inherent built-in electric field, which facilitates accelerated charge transfer and mitigates rapid electron-hole recombination commonly observed in semiconductor systems. Despite substantial progress, current CN-based p-n heterojunctions often suffer from low production yields and limited selectivity in CO₂ photoreduction, presenting significant barriers to efficient CO₂ conversion.

Tellurium (Te), a typical p-type semiconductor, demonstrates excellent properties such as a rapid photoelectric response, strong light absorption and high carrier mobility, making it suitable for various applications. Additionally, Te exhibits good CO₂ adsorption capacity, presenting further promise for its integration into CO₂ reduction processes. Therefore, leveraging the synergy between Te and CN to develop efficient p-n heterojunctions could address existing limitations and maximize the effectiveness of CO₂ photoreduction.

In a study published in Advanced Powder Materials, researchers from Shanghai University in China, and Nanyang Technological University in Singapore, introduced a novel p-n heterojunction photocatalyst comprising ultrasmall Te nanoparticles and CN nanosheets, achieving nearly 100% CO₂ conversion selectivity to CO.

“This is the first attempt to combine Te nanoparticles with CN nanosheets to create a p-n heterojunction that enhances electron-hole separation through a strong built-in electric field, achieving impressive results in photocatalytic CO₂ reduction,” shares Liang Wang, senior and corresponding author of the study.

The team demonstrated the robust internal electric field of the p-n heterojunction accelerates electron transfer from Te nanoparticles to nitrogen sites on CN nanosheets, significantly reducing electron-hole recombination and enhancing CO₂ reduction efficiency.

“The newly engineered p-n heterojunction achieves gas-solid photocatalytic CO₂ conversion to CO without the need for sacrificial agents, reaching a yield of up to 92.0 μmol g^-1 h^-1 with nearly 100% selectivity. This performance surpasses that of most photocatalysts reported to date under similar conditions,” adds Wang.

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Contact the author: Liang Wang (wangl@shu.edu.cn). Institute of Nanochemistry and Nanobiology, School of Environmental and Chemical Engineering, Shanghai University, 99 Shangda Road, BaoShan District, Shanghai 200444, P. R. China. Zheng Liu (Z.Liu@ntu.edu.sg). School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.

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