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. 2023 Feb 24;8(9):8303-8319.
doi: 10.1021/acsomega.2c06717. eCollection 2023 Mar 7.

The Role of the Ferroelectric Polarization in the Enhancement of the Photocatalytic Response of Copper-Doped Graphene Oxide-TiO2 Nanotubes through the Addition of Strontium

Nuhad Abdullah Alomair  1   2 , Nouf Saleh Al-Aqeel  1   2 , Sanaa Saad Alabbad  1 , Hafedh Kochkar  1   2 , Gilles Berhault  3 , Muhammad Younas  4 , Fathi Jomni  5 , Ridha Hamdi  2 , Ismail Ercan  6
Affiliations

The Role of the Ferroelectric Polarization in the Enhancement of the Photocatalytic Response of Copper-Doped Graphene Oxide-TiO2 Nanotubes through the Addition of Strontium

Nuhad Abdullah Alomair et al. ACS Omega. .

Abstract

To evaluate the potential role of in situ formed Sr-Ti-O species as a ferroelectric component able to enhance the photocatalytic properties of an adjacent TiO2 semiconductor, Cu-doped/graphene oxide (GO)/TiO2 nanotubes (TiNTs) composites (with 0.5 wt % Cu and 1.0 wt % GO) have been synthesized while progressive amounts of strontium (up to 1.0 wt %) were incorporated at the surface of the composite through incipient wetness impregnation followed by post-thermal treatment at 400 °C. The different resulting photocatalytic systems were then first deeply characterized by means of N2 adsorption-desorption measurements, X-ray diffraction (XRD), UV-vis diffuse reflectance (UV-vis DR), Raman and photoluminescence (PL) spectroscopies, and scanning electron microscopy (SEM) (with energy-dispersive X-ray (EDX) spectroscopy and Z-mapping). In a second step, optimization of the kinetic response of the Sr-containing composites was performed for the formic acid photodegradation under UV irradiation. The Sr-containing Cu/GO/TiNT composites were then fully characterized by electrochemical impedance spectroscopy (EIS) for their dielectric properties showing clearly the implication of polarization induced by the Sr addition onto the stabilization of photogenerated charges. Finally, a perfect correlation between the photocatalytic kinetic evaluation and dielectric properties undoubtedly emphasizes the role of ferroelectric polarization as a very valuable approach to enhance the photocatalytic properties in an adjacent semiconductor.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
(A) XRD patterns of the xwt%Sr-Cu-GO-TiNT nanomaterials with comparison to the copper-free GO-TiNT and the Sr-free Cu-GO-TiNT: (a) GO-TiNT, (b) Cu-GO-TiNT, (c) 0.2wt%Sr-Cu-GO-TiNT, (d) 0.4wt%Sr-Cu-GO-TiNT, (e) 0.6wt%Sr-Cu-GO-TiNT, (f) 0.8wt%Sr-Cu-GO-TiNT, and (g) 1.0wt%Sr-Cu-GO-TiNT. (B) Zoom in of the region of the (101) anatase reflection showing the absence of shift consecutively to the addition of strontium. (C) (f) 0.8wt%Sr-Cu-GO-TiNT, and (h) 0.8wt%Sr-Cu-GO-TiNT after photocatalytic test.
Figure 2
Figure 2
(A) N2 adsorption–desorption isotherms of the xwt%Sr-Cu-GO-TiNT nanomaterials with comparison to the Sr-free Cu-GO-TiNT and (B) BJH pore size distribution plot derived from the desorption branch with (a) GO-TiNT, (b) Cu-GO-TiNT, (c) 0.2wt%Sr-Cu-GO-TiNT, (d) 0.4wt%Sr-Cu-GO-TiNT, (e) 0.6wt%Sr-Cu-GO-TiNT, (f) 0.8wt%Sr-Cu-GO-TiNT, and (g) 1.0wt%Sr-Cu-GO-TiNT.
Figure 3
Figure 3
(A) Raman spectra of the xwt%Sr-Cu-GO-TiNT materials: (a) Cu-GO-TiNT, (b) 0.2wt%Sr-Cu-GO-TiNT, (c) 0.4wt%Sr-Cu-GO-TiNT, (d) 0.6wt%Sr-Cu-GO-TiNT, (e) 0.8wt%Sr-Cu-GO-TiNT, and (f) 1.0wt%Sr-Cu-GO-TiNT. (B) Zoom in to the region of the E1g active mode of anatase showing the presence of shift effects with the addition of strontium.
Figure 4
Figure 4
UV–vis diffuse reflectance spectra of the xwt%Sr-Cu-GO-TiNT materials with comparison to TiNT, GO-TiNT, and Cu-GO-TiNT: (a) TiNT, (b) GO-TiNT, (c) Cu-GO-TiNT, (d) 0.2wt%Sr-Cu-GO-TiNT, (e) 0.4wt%Sr-Cu-GO-TiNT, (f) 0.6wt%Sr-Cu-GO-TiNT, (g) 0.8wt%Sr-Cu-GO-TiNT, and (h) 1.0wt%Sr-Cu-GO-TiNT.
Figure 5
Figure 5
SEM images of (A) Cu-GO-TiNT, (B) 0.4wt%Sr-Cu-GO-TiNT, (C) 0.6wt%Sr-Cu-GO-TiN,T and (D) 0.8wt%Sr-Cu-GO-TiNT.
Figure 6
Figure 6
EDX mapping analysis of (A) Cu-GO-TiNT (given as reference) and (B) 0.4wt%Sr-Cu-GO-TiNT.
Figure 7
Figure 7
Photoluminescence spectra of TiNT, GO-TiNT, and Cu-GO-TiNT used as references.
Figure 8
Figure 8
Photoluminescence spectra of the xwt%Sr-Cu-GO-TiNT materials with x varying between 0.2 and 1.0 wt % Sr.
Figure 9
Figure 9
Correlation between predicted C/C0 obtained by the nonlinear regression model (with kn = 0.075 min–1 and n = 1.9) vs experimental C/C0 values in the case of the 0.4wt%Sr-Cu-GO-TiNT material.
Figure 10
Figure 10
Variation of formula image vs time for the 0.4wt%Sr-Cu-GO-TiNT material (a1 = 0.04 min–1 and α = 1.50 × 10–4 min–1): red line (model) and blue squares (experiments).
Figure 11
Figure 11
(A) Nyquist diagrams acquired for the 0.4wt%Sr-Cu-GO-TiNT sample at temperatures of acquisition varying between −10 °C and +60 °C with corresponding fitting simulations and representation of the equivalent electric circuit and (B) Arrhenius plot of ln(σT) vs 1000/T.
Figure 12
Figure 12
(A) Correlation between the kinetic parameter a1 and the dielectric constant ε′ vs strontium loading. (B) Correlation between the modified kinetic term (a1*τd) including intradiffusion and the dielectric constant ε′ vs strontium loading.
See this image and copyright information in PMC

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