Fundamental Analysis of Piezocatalysis Process on the Surfaces of Strained Piezoelectric Materials

Abstract

Recently, the strain state of a piezoelectric electrode has been found to impact the electrochemical activity taking place between the piezoelectric material and its solution environment. This effect, dubbed piezocatalysis, is prominent in piezoelectric materials because the strain state and electronic state of these materials are strongly coupled. Herein we develop a general theoretical analysis of the piezocatalysis process utilizing well-established piezoelectric, semiconductor, molecular orbital and electrochemistry frameworks. The analysis shows good agreement with experimental results, reproducing the time-dependent voltage drop and H2 production behaviors of an oscillating piezoelectric Pb(Mg1/3Nb2/3)O3-32PbTiO3 (PMN-PT) cantilever in deionized water environment. This study provides general guidance for future experiments utilizing different piezoelectric materials, such as ZnO, BaTiO3, PbTiO3, and PMN-PT. Our analysis indicates a high piezoelectric coupling coefficient and a low electrical conductivity are desired for enabling high electrochemical activity; whereas electrical permittivity must be optimized to balance piezoelectric and capacitive effects.

Piezo‐Catalytic Effect on the Enhancement of the Ultra‐High Degradation Activity in the Dark by Single‐ and Few‐Layers MoS2 Nanoflowers

“…To quantitatively understand the piezoelectric potential induced electric fi eld by the spontaneous polarization through the single-and few-layer MoS 2 NFs, Equation ( 5) can explain the total strain-induced potential energy shift across the semiconductor. [ 23 ] …”

“…Therefore, this piezoelectric potential which modulates the energetics of the valence band and conduction band across the piezoelectric MoS 2 semiconductor, can have a dramatic effect on the catalyst's interaction with its environment. [ 23 ] The maximum concentration of the adsorbed molecules on the semiconductor's surface is given by Equation ( 6) in order to estimate the relationship between the dopant density of the semiconductor and the adsorbed molecules.…”

“…[ 23,24 ] Therefore, when the non-centrosymmetric structure of the catalyzing material was applied by an external force, an electric fi eld was instantly built up inside the piezoelectric crystal due to its spontaneous polarization, which can effi ciently separate the free carriers of the electron and hole to trigger the catalyzing process for destroying the organic matters in the dark.In this work, the MoS 2 nanofl owers (NFs) are discovered for the fi rst time to have a highly effi cient piezo-catalyst effect, which can dramatically improve their degradation activity for destructing the organic dyes by imposing an ultrasonic wave in the dark. The piezoresponse force microscopy (PFM) revealed that a signifi cant amount of piezoelectric potential generated on the edge sites of the abundantly single-and few-layer MoS 2 NFs.…”

Coupling of piezoelectric effect with electrochemical processes

“…One such heterojunction that is particularly dynamic is that which exists between a piezoelectric material and a chemical solution [6,7]. Piezoelectric fields have been used to control the corrosion rate of materials exposed to etchant solutions [8][9][10][11][12][13][14][15][16][17][18], selectively control the energetics and spatial separation of adsorbed [19,20] and photo-deposition materials [21][22][23][24][25][26][27][28], and have even been used to directly drive electrochemical reactions across piezoelectric/solution interface [6,7,[29][30][31].…”

“…With sufficient shifts in the energies of these states, it is possible to drive the flow of electrons from the piezoelectric's surface to species in solution or from species in solution to the piezoelectric's surface (Fig. 4e) [7]. In pyroelectric and ferroelectric materials, the presence of a spontaneously dipole means an electric field, and its associated electronic distortion, is present throughout the material even in the absence of an applied strain.…”