Nano‐Ferroelectric for High Efficiency Overall Water Splitting under Ultrasonic Vibration

Abstract

Piezocatalysis,converting mechanical vibration into chemical energy,h as emerged as ap romising candidate for water-splitting technology.H owever,t he efficiency of the hydrogen production is quite limited. We herein report welldefined 10 nm BaTiO 3 nanoparticles (NPs) characterized by al arge electro-mechanical coefficient which induces ah igh piezoelectric effect. Atomic-resolution high angle annular dark field scanning transmission electron microscopy(HAADF-STEM) and scanning probe microscopy(SPM) suggests that piezoelectric BaTiO 3 NPs displayac oexistence of multiple phases with lowe nergy barriers and polarization anisotropy which results in ahigh electro-mechanical coefficient. Landau free energy modeling also confirms that the greatly reduced polarization anisotropyf acilitates polarization rotation. Employing the high piezoelectric properties of BaTiO 3 NPs,w e demonstrate an overall water-splitting process with the highest hydrogen production efficiency hitherto reported, with aH 2 production rate of 655 mmol g À1 h À1 ,whichcould rival excellent photocatalysis system. This study highlights the potential of piezoelectric catalysis for overall water splitting.

Ultrasmall Barium Titanate Nanoparticles for Highly Efficient Hypoxic Tumor Therapy via Ultrasound Triggered Piezocatalysis and Water Splitting

“…After 5 min of irradiation with ultrasound (US; 1 MHz, 1 w/cm 2 , 50% duty cycle), little O 2 production was observed for the 200 nm BTO group and BTO nanowire group, which should be due to the piezoelectric potential in both of these groups not reaching the energy for water splitting (1.23 eV). 27 In contrast, the O 2 concentration in the US+P-BTO group was nearly 1.5 times higher than that in the control group, P-BTO group, US group, the 200 nm BTO group, and BTO nanowire group. These results suggested that O 2 generation was attributed to the P-BTO nanoparticles irradiated by ultrasound, indicating that ultrasmall barium titanate could be used for the O 2 production in tumor treatment.…”

“…As a result, the imbalanced charges will induce redox reaction with the water molecules to produce O 2 and ROS (Figure 3a). 27 A dissolved oxygen meter (AZ8403, China) was used to measure the O 2 generation in deoxygenated deionized water. Six groups were set to verify the piezocatalytic water-splitting ability of P-BTO nanoparticles (Figure 3b).…”

“…24−26 As a result, the excess charges could induce at least two redox reaction behaviors: (1) The released charges could directly react with the water molecules to produce O 2 . 27 (2) The released charges could also combine with water molecules or O 2 to produce ROS. 28 On the contrary, when the agitating mechanical force decreases, charges will be adsorbed from the surrounding electrolyte to balance the bound charges induced by the piezoelectric effect, which will also trigger two reaction behaviors: (1) The charges in the electrolyte are attracted to the surfaces of barium titanate to induce high surface potential for water splitting to produce O 2 .…”

“…28 On the contrary, when the agitating mechanical force decreases, charges will be adsorbed from the surrounding electrolyte to balance the bound charges induced by the piezoelectric effect, which will also trigger two reaction behaviors: (1) The charges in the electrolyte are attracted to the surfaces of barium titanate to induce high surface potential for water splitting to produce O 2 . 27 (2) The charges in the electrolyte with opposite polarity to those of bound charges will participate in the redox reaction to produce ROS again. 28 At present, research about the piezocatalytic effect of barium titanate was mainly focused on tooth whitening, 28 hydrogen production, 27 and bacterial disinfection; 29 its full application in tumor therapy was still in its infancy, especially for using both of its functions of O 2 and ROS generation.…”

“…27 (2) The charges in the electrolyte with opposite polarity to those of bound charges will participate in the redox reaction to produce ROS again. 28 At present, research about the piezocatalytic effect of barium titanate was mainly focused on tooth whitening, 28 hydrogen production, 27 and bacterial disinfection; 29 its full application in tumor therapy was still in its infancy, especially for using both of its functions of O 2 and ROS generation.…”