Gradient Cationic Vacancies Enabling Inner-To-Outer Tandem Homojunctions: Strong Local Internal Electric Field and Reformed Basic Sites Boosting CO2 Photoreduction

Yinghui Wang; Jingcong Hu; Teng Ge; Fang Chen; Yue Lu; Runhua Chen; Hongjun Zhang; Bangjiao Ye; Shengyao Wang; Yihe Zhang; Tianyi Ma; Hongwei Huang

doi:10.1002/adma.202302538

Gradient Cationic Vacancies Enabling Inner-To-Outer Tandem Homojunctions: Strong Local Internal Electric Field and Reformed Basic Sites Boosting CO₂ Photoreduction

Adv Mater. 2023 Aug;35(31):e2302538. doi: 10.1002/adma.202302538. Epub 2023 Jun 25.

Authors

Yinghui Wang¹, Jingcong Hu², Teng Ge³, Fang Chen¹, Yue Lu², Runhua Chen⁴, Hongjun Zhang⁴, Bangjiao Ye⁴, Shengyao Wang⁵, Yihe Zhang¹, Tianyi Ma⁶, Hongwei Huang¹

Affiliations

¹ Engineering Research Center of Ministry of Education for Geological Carbon Storage and Low Carbon Utilization of Resources, Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing, 100083, China.
² Beijing Key Laboratory of Microstructure and Properties of Solids Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing, 100124, China.
³ Engineering Technology-Research Center of Henan Province for Solar Catalysis, College of Chemistry and Pharmaceutical Engineering, Nanyang Normal University, Nanyang, 473061, China.
⁴ State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei, 230026, China.
⁵ College of Science, Huazhong Agricultural University, Wuhan, 430070, China.
⁶ School of Science, RMIT University, Melbourne, VIC, 3000, Australia.

PMID: 37120752
DOI: 10.1002/adma.202302538

Abstract

The slow charge dynamics and large activation energy of CO₂ severely hinder the efficiency of CO₂ photoreduction. Defect engineering is a well-established strategy, while the function of common zero-dimensional defects is always restricted to promoting surface adsorption. In this work, a gradient layer of tungsten vacancies with a thickness of 3-4 nm is created across Bi₂ WO₆ nanosheets. This gradient layer enables the formation of an inner-to-outer tandem homojunction with an internal electric field, which provides a strong driving force for the migration of photoelectrons from the bulk to the surface. Meanwhile, W vacancies change the coordination environment around O and W atoms, leading to an alteration in the basic sites and the mode of CO₂ adsorption from weak/strong adsorption to moderate adsorption, which ultimately decreases the formation barrier of the key intermediate *COOH and facilitates the conversion thermodynamics for CO₂ . Without any cocatalyst and sacrificial reagent, W-vacant Bi₂ WO₆ shows an outstanding photocatalytic CO₂ reduction performance with a CO production rate of 30.62 µmol g^-1 h^-1 , being one of the best catalysts in similar reaction systems. This study reveals that gradient vacancies as a new type of defect will show huge potential in regulating charge dynamics and catalytic reaction thermodynamics.

Keywords: CO2 photoreduction; basic sites; gradient vacancies; internal electric field; tandem homojunctions.

Abstract

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