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. 2023 Jun 16;28(12):4798.
doi: 10.3390/molecules28124798.

Effect of the Synthetic Parameters over ZnO in the CO2 Photoreduction

Danny Zanardo  1   2 , Giulia Forghieri  1 , Elena Ghedini  1 , Federica Menegazzo  1 , Alessia Giordana  3 , Giuseppina Cerrato  3 , Elti Cattaruzza  4 , Alessandro Di Michele  5 , Giuseppe Cruciani  6 , Michela Signoretto  1
Affiliations

Effect of the Synthetic Parameters over ZnO in the CO2 Photoreduction

Danny Zanardo et al. Molecules. .

Abstract

Zinc oxide (ZnO) is an attractive semiconductor material for photocatalytic applications, owing to its opto-electronic properties. Its performances are, however, strongly affected by the surface and opto-electronic properties (i.e., surface composition, facets and defects), in turn related to the synthesis conditions. The knowledge on how these properties can be tuned and how they are reflected on the photocatalytic performances (activity and stability) is thus essential to achieve an active and stable material. In this work, we studied how the annealing temperature (400 °C vs. 600 °C) and the addition of a promoter (titanium dioxide, TiO2) can affect the physico-chemical properties of ZnO materials, in particular surface and opto-electronic ones, prepared through a wet-chemistry method. Then, we explored the application of ZnO as a photocatalyst in CO2 photoreduction, an appealing light-to-fuel conversion process, with the aim to understand how the above-mentioned properties can affect the photocatalytic activity and selectivity. We eventually assessed the capability of ZnO to act as both photocatalyst and CO2 adsorber, thus allowing the exploitation of diluted CO2 sources as a carbon source.

Keywords: carbon dioxide adsorber; carbon dioxide photoreduction; opto-electronic properties; surface properties; zinc oxide.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) XRD diffractograms and (b) N2 physisorption isotherms of ZnO materials.
Figure 2
Figure 2
(a–c) SEM images of 4CSZ at different magnifications and SEM images of (d) T4CSZ, (e) 4TCSZ, (f) 6CSZ.
Figure 3
Figure 3
HR-TEM images of (a) 4CSZ, (b) 6CSZ, (c) T4CSZ and (d) 4TCSZ. Insets to Figure 3a,b refer to low-magnification situations, whereas the black images with bright spots in all images refer to FFT elaboration, i.e., virtual electron diffraction patterns, for all samples.
Figure 4
Figure 4
(a) O1s and (b) C1s XPS signals of ZnO materials.
Figure 5
Figure 5
(a) ATR-FTIR spectra and (b) UV-vis absorption spectra (Kubelka–Munk function) of ZnO materials. The asterisk on ATR-FTIR spectra point out the δO−H shoulder.
Figure 6
Figure 6
(a) Steady-state PL spectra and (b) TR-PL graph of the visible emissions (λEM = 641 nm) of ZnO-based samples.
Figure 7
Figure 7
Proposed band diagram and visible emission mechanisms of ZnO materials.
Figure 8
Figure 8
(a) TOF of CH4 and O2 and (b) TOF of CH4 normalized by the SSA (TOF*) of ZnO samples.
Figure 9
Figure 9
Reaction tests and re-cycles of the T4CSZ catalyst with a CO2-free reaction medium. The used catalyst was exposed to a dark CO2 flow prior to the 2nd, 3rd and 4th runs.
See this image and copyright information in PMC

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