<h1 class="pgc-h-arrow-right" data-track="1" > Professor Zhang Lizhi's team Nat Commun: Photocatalytic CO2 conversion in pure water at the Band Gap BiOCl atomic layer of Fu van Der Waal</h1>
Photocatalytic CO2 reduction reactions can use solar energy to convert large amounts of "greenhouse gas" CO2 in the air into high value-added chemicals, fuels and industrial feedstocks, and have shown great application potential in solving the energy crisis and alleviating the greenhouse effect. The use of photocatalytic processes to capture and convert waste CO2 gases in the atmosphere can effectively cut off the carbon cycle caused by human activities, thereby achieving sustainable development in the social production process. However, in industrial production, the large-scale promotion of green and economical photocatalytic CO2 reduction processes still faces many problems. For example, CO2 catalytic reduction reactions are more likely to occur in KHCO3 solutions or organic solvents such as acetonitrile/dimethylformamide. Although the use of organic solvents can increase the solubility, reaction effectiveness and activity of CO2 in solution to some extent, it can also lead to increased experimental costs and potential risks. At present, the most ideal CO2 reduction technology route is to reduce CO2 molecules in pure water using semiconductor materials under visible light irradiation. However, compared with reaction systems using organic solvents, adding cocatalysts and using hole sacrifice agents, the activity of photocatalytic CO2 reduction reactions in pure water is usually less than 50 μmol g-1 h-1, mainly due to the difficulty of direct dissociation of strong excitons into free carriers at room temperature, and the lack of sufficient catalytically active sites on the surface of the material. It is of great significance to rationally design semiconductor materials that can efficiently dissociate excitons into free carriers at room temperature and contain rich catalytic sites on the surface, which is of great significance for realizing the photocatalytic CO2 reduction process in pure water.
Recently, Professor Zhang Lizhi's team of Central China Normal University used the Fu Van Der Waal band gap BiOCl atomic layer to achieve photocatalytic CO2 reduction in pure water, (1) the first time through the bulk phase doped carbon atoms and water vapor at high temperature synthesis reaction (C(s) + H2O(g) → H2(g) + CO(g)) driven gas phase stripping strategy to regulate the number of BiOCl layered structures and regulate the proportion of van Der Waal band gap exposure on the surface ;(2) The number of layered structures of BiOCl nanosheets determines the proportion of van der Waal band gap exposure, and its exciton stability is inversely proportional to the van der Waal band gap exposure ratio. That is, BiOCl nanosheets with fewer layers can greatly reduce the stability of excitons in the material, induce the binding excitons formed by electrons and holes under the force of Coulomb to re-dissociate them into free carriers; (3) the increase in van Der Waals band gap exposure ratio can effectively reduce the oxygen vacancy formation energy on the surface of BiOCl nanosheets. This work proposes a gas-phase stripping strategy driven by syngas-like synthesis reactions to manipulate van der Waals band gap exposure ratios, providing a new strategy to optimize the photocatalytic performance of layered semiconductor materials.
Figure 1. Rich Van Der Waals bandgap exposure BOC-VDWGs-AL nanosheet structure characterization: (a) TEM image, (b) darkfield STEM image, (c-e) Bi, O and Cl elements mapping imaging, (f) AFM image, (g) theoretical crystal structure, (h) HAADF-STEM image, (i) conversion from (h) to BOC-VDWGs-AL nanosheet three-dimensional intensity color map and (j) corresponding intensity trend, (k) Positron annihilation spectra (illustrated as a simulated VDWG-Bi-VO••-Bi positron density distribution), (l) EPR spectra, (m) Bi L3-side X-ray absorption fine spectra, (n) O-K-side X-ray absorption proximal spectra.
For the first time, the authors were able to regulate the number of layered structures by a gas-like synthesis reaction (C(s)+ H2O(g)→ H2(g) + CO(g)) driven by a synthesis gas-like synthesis reaction (C(s)+ H2(g) occurred at high temperatures by bulk phase doped carbon atoms and water vapor, and then the proportion of van der Waals band gap exposure in BiOCl nanosheets. As the exposure ratio of van der Waals band gap increases, a large number of Bi-VO••-Bi defects are generated on the surface of BiOCl nanosheets, eventually forming the "VDWG-Bi-VO••-Bi" association (Figure 1).
Figure 2. Fu van Der Waal bandgap BOC-VDWGs-AL nanosheets photocatalytic reduction of CO2 performance in pure water: (a) photocatalytic CO2 reduction in pure water, the control experiments are BOC-VDWGs-AL nanosheets under visible irradiation to reduce CO2 in pure water, visible irradiation does not contain catalyst and CO2 gas saturated pure water, BOC-VDWGs-AL nanosheets reduce CO2 gas in pure water under no light conditions and BOC-VDWGs-AL nanosheets reduce Ar saturated pure water under visible irradiation; (b) BOC-VDWGs-AL nanosheets photocatalytic CO2 reduction cycle test within 50 hours; (c) Analysis of BOC-VDWGs-AL nanosheets to reduce 13CO2 gas in pure water under visible light irradiation by gas chromatography-mass spectrometry; (d) (e) Statistical results of CO/O2 molar ratio generated in the photocatalytic reduction of CO2 in BOC-VDWGs-AL nanosheets; (f) COMPARISON OF CO2 co2 generation by photocatalytic reduction of CO2 by BOC-VDWGs-AL, CBOC-VDWGs and BOC-VDWGs-76 nanosheets under visible light irradiation; Comparison of THE RATE AT WHICH BOC-VDWGS-AL nanosheets and other layered photocatalysts photocatalytically reduce CO2 in pure water to produce CO.
After a 5-hour continuous reaction, the BOC-VDWGs-AL nanosheets have a rate of 900 μmol g−1 for photocatalytic CO2 reduction in pure water, and the selectivity of CO products exceeds 97% (Figure 2). After 50 hours of continuous photocatalytic CO2 reduction reaction, BOC-VDWGs-AL nanosheets still have good photocatalytic CO2 reduction to produce CO activity.
Figure 3. Analysis of boc-VDWGs-AL atomic layer exciton dissociation and bulk phase charge separation efficiency: (a) BOC-VDWGs-AL atomic layer and (b) BOC-VDWGs-76-VO•• nanosheet temperature-dependent steady-state fluorescence emission spectra; (c) linear dependence between van der Waals band gap exposure ratio and exciton binding energy; (d) exciton binding energy of common layered materials; (e) time-resolved transient fluorescence emission spectra; (f) transient photocurrent response density; (g) Bulk phase charge separation efficiency.
The exciton binding energy of the synthesized sample gradually decreases as the proportion of van der Waals band gap exposure increases. When the van der Waal band gap exposure ratio on the surface of the BiOCl nanosheet increased from 76% (BOC-VDWGs-76-VO••) to 99% (BOC-VDWGs-AL), the exciton binding energy of the BOC-VDWGs-AL nanosheet was reduced by 3.8 times to only 36 meV, which was significantly smaller than other layered semiconductor materials (about 80-280 meV) (Figure 3).
Figure 4. The binding structure of VDWG-Bi-VO••-Bi promotes the conversion of CO2 to CO2: (a1) C-O bond length and O-C-O angle in linear CO2 molecules; CO2 molecule adsorption in (a2) VDWG-Bi-O-Bi and (a3) C-O bond length and O-C-O angle on VDWG-Bi•-Bi structure; (b1) CO2 molecule adsorption configuration after "VDWG-Bi-Vo••-Bi" connective structure surface optimization and (b2) (c) Gibbs free energy changes in the formation of intermediate products during the catalytic conversion of CO2 molecules on VDWG-Bi-O-Bi and VDWG-Bi-VO••-Bi structures; (d) CO2-VDWGs-AL nanosheets and BOC-VDWGs-AL-O2 nanosheets CO2-TPD curves; (e) In situ infrared spectra were generated during photocatalytic CO2 reduction of BOC-VDWGs-AL nanosheets; (f) *IN IN-situ infrared signal intensities of CO on BOC-VDWGs-AL nanosheets and BOC-VDWGs-AL-O2 nanosheets; (g) CO-TPD curves corresponding to BOC-VDWGs-AL nanosheets and BOC-VDWGs-AL-O2 nanosheets.
CO2 molecules are transformed into CO molecules by similar reaction pathways on VDWG-Bi-O-Bi and VDWG-Bi-VO••-Bi structures (Figure 3.24). Among them, the *COOH intermediate lysis process (*COOH → *CO + *OH) is the rapid step of the whole reaction. *The formation barrier of COOH intermediates on the VDWG-Bi-VO••-Bi structure is 1.27 eV, which is 1.51 eV lower than the formation barrier (2.78 eV) on the VDWG-Bi-O-Bi structure, that is, the oxygen vacancy in the VDWG-Bi-VO••-Bi structure can promote the cleavage of the *COOH intermediate. In addition, the oxygen vacancy can also accelerate the desorption of *CO intermediates from the surface of the catalyst, that is, the *CO → CO desorption process on the VDWG-Bi-VO••-Bi structure will release 0.39 eV energy. Conversely, on the VDWG-Bi-O-Bi structure, the *CO → CO desorption process requires the absorption of 0.57 eV energy.
The results were recently published in Nature Communications, and the first authors were Dr. Yanbiao Shi, Dr. Jie Li, and Dr. Chengliang Mao, School of Chemistry, Central China Normal University.
Van der Waals Gap-Rich BiOCl Atomic Layers Realizing Efficient, Pure-Water CO2-to-CO Photocatalysis
Yanbiao Shi, Jie Li*, Chengliang Mao, Song Liu, Xiaobing Wang, Xiufan Liu, Shengxi Zhao, Xiao Liu, Yanqiang Huang and Lizhi Zhang*
Nat. Common., 2021, 12, 5923, DOI: 10.1038/s41467-021-26219-6
Mentor Profile
Professor Zhang Lizhi, winner of the National Science Foundation for Outstanding Young Scholars, Jiang Scholar Distinguished Professor of the Ministry of Education, Leading Talents of Science and Technology Innovation in the Young and Middle-Aged Science and Technology Innovation Leading Talents Program of the Ministry of Science and Technology, and Leading Talents in Scientific and Technological Innovation of the 10,000 Talents Program of the Central Organization Department. Professor Zhang Lizhi's main research interests are pollution control chemistry, photocatalysis, and environmental catalytic materials. It has been granted more than 30 patents. In Chem, Acc. Chem. Res.、Nature Commun.、JACS、Angew. Chem.、Adv. Mater., ES&T and other SCI-source academic journals have published more than 290 papers, of which 27 have been selected as highly cited papers in ESI. As of May 2020, the paper has been cited more than 22,680 times, he has cited more than 21,900 times, and the H index is 99. In 2008, he won the second prize of natural science in Hubei Province (the first completer), in 2010 he won the Elsevier Environmental Science Field 2005-2010 Highly Cited Chinese Author Award, in 2011 he won the Hubei Youth Science and Technology Award, in 2011 he was selected as the "Double Hundred Plan" of Hubei Province Independent Innovation, in 2012 he was selected into the Hubei Provincial High-end Talent Leadership Training Program and the Hubei Provincial High-level Talent Project, and since 2014 he has been continuously selected for The Release of Elsevier" List of Highly Cited Scholars in China in the Field of Chemistry", won the second prize of natural science of the Ministry of Education's Outstanding Achievement Award for Scientific Research (Science and Technology) in 2015 (the first completer), won the second prize of natural science of the Ministry of Education in 2016, and was continuously selected into the list of global highly cited scientists in the cross-field of Claivate (Web of Science) from 2018 to 2020. In 2019, he won the first prize of natural science in Hubei Province (the first person to complete it).
Zhang Lizhi
https://www.x-mol.com/university/faculty/10804
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