BaTiO₃ Nanosheets and Caps Grown on TiO₂ Nanorod Arrays as Thin-Film Catalysts for Piezocatalytic Applications

Abstract

Powder-form piezocatalysts suffer from poor recyclability and pose a potential threat of creating serious secondary pollution, which restrict their practical applications. Thin-film piezocatalysts, which not only exhibit good recyclability but also fully contact with solution, are believed to be one of the solutions to address these problems. In this work, the nanostructured BaTiO3 (BTO) thin films were fabricated by a facile hydrothermal method for their potential applications in piezocatalysis. The vertically standing BTO nanosheets grown on the top of TiO2 nanorod arrays exhibited superior piezocatalytic performance as well as piezo-electrochemical property. Given the different strain states between thin-film piezocatalyst and powder-form piezocatalyst, both the impact force of water and isostatic pressure are taken into consideration in finite element method (FEM) simulation. The FEM simulation shows that a stronger piezoelectric filed can be built in BTO nanosheets because of their easier deformation, and thus can lead to a higher piezocatalytic degradation efficiency. Our work presented here is expected to provide a potential route for the nanoengineering of thin-film piezocatalysts and clarify the catalytic mechanism for substrate-fixed piezocatalysts.

Piezocatalytic Foam for Highly Efficient Degradation of Aqueous Organics

“…It is reported that tert ‐butanol (TBA) is a free radical scavenger which consumes the ⋅OH radicals in solution. [ 33,39,42,61 ] After the addition of TBA, the piezocatalytic efficiency is dramatically reduced (Figure 4d). On the other hand, the ferrous ions (Fe 2+ ) can accelerate the generation of ⋅OH through the Fenton reaction, [ 11,62,63 ] thereby improving the piezocatalytic efficiency in our system (Figure 4d).…”

“…Upon ultrasonic treatment, bubbles emerge in the solution and collapse, which can inflict a high pressure (≈10 8 Pa) and further generate piezoelectric dipoles (electrons, e − , and holes, h + ) on the foam surface. [ 33,39,42,61 ] As the energy level of the conduction band is −0.83 V (vs the normal hydrogen electrode, NHE) for BaTiO 3 , the piezoelectric electrons are able to reduce the dissolved O 2 to ⋅O 2 − (with a standard redox potential of −0.33 V vs NHE). On the other hand, the energy level for the valence band is 2.31 V versus NHE, by which the piezoelectric holes are capable of oxidizing OH − to ⋅OH (with a standard redox potential of 1.9 V vs NHE) in solution.…”

“…Furthermore, they tend to diffuse and cause secondary pollution in natural water bodies, which greatly restrict their applicability in practical water treatment. [ 41–44 ] Therefore, it would be ideal to embed piezoelectric materials in the form of a free‐standing scaffold, where piezocatalytic process could take place under the strike of the water flow ( Figure a). However, the supporting scaffolds of integral piezocatalytic platforms are usually piezoelectrically inert, which only limits the deformation of piezocatalysts and reduces the accessibility of pollutants to the reaction sites.…”

“…As a result, the piezocatalytic efficiency of an integral platform is usually inferior to that of piezoelectric nanoparticles. [ 41,42 ] Acquah and coworkers embedded ZnO nanoparticles in carbon nanotube (CNT) paper for degrading methylene blue (MB) in water, whereas only 12% of the total MB decomposed after ultrasonic treatment for 140 min. [ 43 ] For the aforementioned TMD nanoflowers with an ultrahigh piezocatalytic efficiency, when embedded into the polydimethylsiloxane (PDMS) substrate, the time for complete RhB degradation increases by more than one order.…”

Synergetic contribution of enriched selenium vacancies and out-of-plane ferroelectric polarization in AB-stacked MoSe2 nanosheets as efficient piezocatalysts for TC degradation

“…1 Over the past few years, typical piezoelectric nanomaterials have been exploited, including ZnO, Bi 4 Ti 3 O 12 , BaTiO 3 , Bi 0.5 Na 0.5 TiO 3 , C 3 N 4 , BN, WS 2 , and MoS 2 . [2][3][4][5][6][7][8][9][10] Among these materials, two-dimensional (2D) transition metal dichalcogenides (TMDs) have demonstrated excellent piezocatalytic performance in water splitting, contaminant degradation, carbon dioxide reduction, polymerization reaction and disease treatment due to their large piezoelectric coefficients, inherent layered crystal structures and high mechanical flexibility (that can withstand large strain). 11 However, their insufficient active sites and poor electrical conductivity hinder the improvement of their piezocatalytic efficiency.…”