Controlled Porosity in Ferroelectric BaTiO₃ Photoanodes

Abstract

The use of ferroelectric polarization to promote electron–hole separation has emerged as a promising strategy to improve photocatalytic activity. Although ferroelectric thin films with planar geometry have been largely studied, nanostructured and porous ferroelectric thin films have not been commonly used in photo-electrocatalysis. The inclusion of porosity in ferroelectric thin films would enhance the surface area and reactivity, leading to a potential improvement of the photoelectrochemical (PEC) performance. Herein, the preparation of porous barium titanate (pBTO) thin films by a soft template-assisted sol–gel method is reported, and the control of porosity using different organic/inorganic ratios is verified by the combination of scanning electron microscopy and ellipsometry techniques. Using piezoresponse force microscopy, the switching of ferroelectric domains in pBTO thin films is observed, confirming that the ferroelectric polarization is still retained in the porous structures. In addition, the presence of porosity in pBTO thin films leads to a clear improvement of the PEC response. By electrochemical poling, we also demonstrated the tuning of the PEC performance of pBTO thin films via ferroelectric polarization. Our work offers a simple and low-cost approach to control the morphology optimization of ferroelectric thin films, which could open up the development of materials with great potential for PEC applications.

Photocatalytic and Photoelectrocatalytic Water Splitting by Porous g-C3N4 Nanosheets for Hydrogen Generation

“…23,24 The separation of photogenerated charge carriers on the surface of the photoelectrode can reduce the electron−hole pair recombination by fabricating highly porous nanostructures. 25 In this context, we have exfoliated bulk g-C 3 N 4 by using sulfuric acid (H 2 SO 4 ) to form highly porous 2D-shaped nanosheets of g-C 3 N 4 , which exhibit a higher surface area than bulk g-C 3 N 4 . Furthermore, we have used two different sacrificial agents, namely, sodium sulfide/ sodium sulfite (Na 2 S/Na 2 SO 3 ) and triethanolamine (TEOA), for a better understanding to enhance the photocatalytic activity toward water-splitting hydrogen generation.…”

“…It is well-known that exfoliation of the bulk material leads to an increase in the pore volume, which is useful for enhancing the BET surface area. , The separation of photogenerated charge carriers on the surface of the photoelectrode can reduce the electron–hole pair recombination by fabricating highly porous nanostructures . In this context, we have exfoliated bulk g-C 3 N 4 by using sulfuric acid (H 2 SO 4 ) to form highly porous 2D-shaped nanosheets of g-C 3 N 4 , which exhibit a higher surface area than bulk g-C 3 N 4 .…”

Enhanced Mechanical Stability and Scratch Resistance of Mesoporous Aluminosilicate Thin Films

“…[68,74] Contrary to more commonly used techniques to study the surface morphology (like scanning electron or atomic force microscopy), EP probes the accessible porosity across the entire film thickness and for a representative sample volume. [66,67,75] Moreover, EP provides also information about pore size distribution and the Youngs modulus. [71] As shown in the Supporting Information (Figure S2), some changes were also observed with the modification over the O:I ratio: 7.2±0.1 nm (AlSi-20); 8.2±0.3 nm (AlSi-30) and 10.0±0.1 nm (AlSi-40), which is in agreement with previous studies, [73] Young's modulus (E) values were obtained from the fitting of the EP measurements (Figure 2D).…”

Highly transparent Bi4Ti3O12 thin-film electrodes for ferroelectric-enhanced photoelectrochemical processes

“…30 Besides photo-catalysis, adopting ferroelectric semiconductors can be particularly effective in photoelectrochemical (PEC) cells as photo-electrode materials, considering the possibility to modify cell efficiency towards the desired reaction by simply polarizing the photo-electrode, thus representing a great operational advantage. A lot of work has been published on the study and development of poled ferroelectric photo-electrode such as BiFeO 3 , [31][32][33][34][35][36][37][38][39][40] BaTiO 3 , [41][42][43][44][45] Li/Na/K-NbO 3 , [45][46][47][48][49] PbTiO 3 -PbZrTiO 3 , 50-53 SrTiO 3 , 54,55 for the PEC water-splitting reaction, but the use of ferroelectric photocathodes for CO 2 PEC reduction has not been exploited yet. On the other hand, some works on the production of BiTO ferroelectric layers have been reported for photovoltaic applications, [56][57][58] and only one preliminary work in photoelectrocatalysis, where thin films BiOI/BiTO electrodes were fabricated via a metering rod method for the photoelectrochemical characterization of this heterostructure, as photo-anode in the ferroelectric-assisted water-splitting reaction.…”

“…A lot of work has been published on the study and development of poled ferroelectric photoelectrodes such as BiFeO 3 , [31][32][33][34][35][36][37][38][39][40] BaTiO 3 , [41][42][43][44][45] Li/Na/K-NbO 3 , [45][46][47][48][49] PbTiO 3 -PbZrTiO 3 , [50][51][52][53] and SrTiO 3 , 54,55 for the PEC water-splitting reaction, but the use of ferroelectric photocathodes for CO 2 PEC reduction has not been exploited yet. On the other hand, some studies on the production of BiTO ferroelectric layers have been reported for photovoltaic applications, [56][57][58] and only one preliminary work on photo-electrocatalysis has been reported, where thin lm BiOI/BiTO electrodes were fabricated via a metering rod method for the photo-electrochemical characterization of this heterostructure, as a photoanode in the ferroelectric-assisted water-splitting reaction.…”