Strain‐Engineered Nano‐Ferroelectrics for High‐Efficiency Piezocatalytic Overall Water Splitting

Abstract

Developing nano‐ferroelectric materials with excellent piezoelectric performance for piezocatalysts used in water splitting is highly desired but also challenging, especially with respect to reaching large piezo‐potentials that fully align with required redox levels. Herein, heteroepitaxial strain in BaTiO3 nanoparticles with a designed porous structure is successfully induced by engineering their surface reconstruction to dramatically enhance their piezoelectricity. The strain coherence can be maintained throughout the nanoparticle bulk, resulting in a significant increase of the BaTiO3 tetragonality and thus its piezoelectricity. Benefiting from high piezoelectricity, the as‐synthesized blue‐colored BaTiO3 nanoparticles possess a superb overall water‐splitting activity, with H2 production rates of 159 μmol g−1 h−1, which is almost 130 times higher than that of the pristine BaTiO3 nanoparticles. Thus, this work provides a generic approach for designing highly efficient piezoelectric nanomaterials by strain engineering that can be further extended to various other perovskite oxides, including SrTiO3, thereby enhancing their potential for piezoelectric catalysis.

The Mechanism of Piezocatalysis: Energy Band Theory or Screening Charge Effect?

“…This signifies that the amplitude of the piezopotential should fully reach or exceed the Gibbs free energy threshold of water splitting to energetically assist the reactions, since it is similar to the onset potential in electrocatalysis. A further verification of the important role of piezopotential was made by comparatively testing the overall water splitting performance of strain‐engineered and normal BaTiO 3 [19] . As shown in Figure 7 e,f, only the strain‐engineered BaTiO 3 can produce H 2 and O 2 as a result of the enhancement of the piezopotential (1.6 V).…”

“…In terms of the positive screening charges,p rotons are considered to be the major species that work as acceptors in piezocatalytic oxidations. [19] Nevertheless,t here are other forms of screening charges,s uch as oxygen vacancies,t hat have received less attention but are also very important for catalytic activity.Anoxygen vacancy (OV) in oxide catalysts provides the active site for redox reactions because of its cationic features. [42] It has been reported that carbon contaminations adsorbed on the external surface can react with lattice oxygen under low temperatures,thereby giving rise to surface OVst hat screen the polarization.…”

“…1]. [11c, 19] …”

“…surface charged adsorbates from an external system). More specifically, piezopotential as the driving force should fully reach or exceed the required Gibbs free energy change of a specific reaction, which is deemed the prerequisite for piezocatalysis [19] . Moreover, another significant characteristic that distinguishes the screening charge effect from the energy band theory is that the charges participating in the redox reactions are surface‐adsorbed screening charges from an external system rather than internal charges from the material.…”

High Efficiency Water Splitting using Ultrasound Coupled to a BaTiO3 Nanofluid

“…[ 26 , 28 , 29 , 30 ] The majority of work to date has focused on morphological design, such as the formation of microfibers, [ 10 , 11 , 25 ] nanowires, [ 27 ] nanosheets, [ 9 , 28 , 29 ] and nanoparticles. [ 16 , 31 , 32 ] Other work has been reported on the exploitation of noble metals as the co‐catalyst [ 29 , 30 , 33 ] and maximizing the polarization change when the working temperature is close to the Curie temperature, T c , of a ferroelectric. [ 34 , 35 ] Recent work by Su et al.…”