Boosted photoreduction of diluted CO 2 through oxygen vacancy engineering in NiO nanoplatelets
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Boosted photoreduction of diluted CO2 through oxygen vacancy engineering in NiO nanoplatelets Weiyi Chen1,§, Xueming Liu1,§, Bin Han1, Shujie Liang1, Hong Deng1,2 (), and Zhang Lin1,2 1
School of Environment and Energy, Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Resource Recycling, South China University of Technology, Guangzhou 510006, China 2 Guangdong Engineering and Technology Research Center for Environmental Nanomaterials, Key Laboratory of Pollution Control and Ecosystem Restoration in Industry Clusters (Ministry of Education), South China University of Technology, Guangzhou 510006, China § Weiyi Chen and Xueming Liu contributed equally to this work. © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 11 August 2020 / Revised: 26 August 2020 / Accepted: 8 September 2020
ABSTRACT Converting carbon dioxide (CO2) to diverse value-added products through photocatalysis can validly alleviate the critical issues of greenhouse effect and energy shortages simultaneously. In particular, based on practical considerations, exploring novel catalysts to achieve efficient photoreduction of diluted CO2 is necessary and urgent. However, this process is extremely challenging owing to the disturbance of competitive adsorption at low CO2 concentration. Herein, we delicately synthesize oxygen vacancy-laden NiO nanoplatelets (r-NiO) via calcination under Ar protection to reduce diluted CO2 through visible light irradiation (> 400 nm) assisted by a Ru-based photosensitizer. Benefitting from the strongly CO2 adsorption energy of oxygen vacancies, which was confirmed by density functional calculations, the r-NiO catalysts exhibit higher activity and selectivity (6.28 × 103 µmol·h−1·g−1; 82.11%) for diluted CO2-to-CO conversion than that of the normal NiO (3.94 × 103 µmol·h−1·g−1; 65.26%). Besides, the presence of oxygen vacancies can also promote the separation of electron-hole pairs. Our research demonstrates that oxygen vacancies could act as promising candidates for photocatalytic CO2 reduction, offering fundamental guidance for the actual photoreduction of diluted CO2 in the future.
KEYWORDS diluted CO2, photocatalytic reduction, oxygen vacancies, NiO nanoplatelets, adsorption
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Introduction
Reduction of CO2 into high value-added hydrocarbon fuels by clean, sustainable solar energy is one of the effective ways to alleviate the severe issues of greenhouse effect and energy crisis simultaneously [1–6]. As its representative technology, photocatalytic CO2 reduction involves the following processes: 1) the electron-hole pairs are excited by photons; 2) the excited electrons transport to the surface catalytic sites; 3) the CO2 molecules adsorbed above the catalytic sites are reduced by electrons [7, 8]. Obviously, the transport of electrons to the catalytic sites is a key step in the photocatalytic CO2 reduction. Transition metal ions with diverse redox states are beneficial compositions to construct electron transport chains for photoreduction CO2
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