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The intrinsic flexoelectric effect observed in oxide materials often falls below the desired threshold for practical applications. In this work, we demonstrate proton doping in insulating rutile TiO2 crystal as an effective approach to significantly increase flexoelectricity by more than two orders of magnitude. We attribute the noteworthy enhancement of flexoelectricity to the dual impact of proton doping in oxide materials. First, proton doping serves to induce the presence of charge carriers, resulting in the generation of flexoelectric currents. Second, proton doping induces expansion and distortion of the lattice structure, leading to an amplified flexoelectric field when the crystal experiences a strain gradient. The formation of O–H bonding in TiO2 crystal provides another route to break centrosymmetry according to lattice distortion of the TiO2 lattice, resulting in a larger flexoelectric field. In addition, the introduction of proton doping in TiO2 single crystals leads to a substantial increase in photocurrent by effectively flattening the interfacial Schottky junction. This phenomenon results in a three-order of magnitude enhancement of the photocurrent. Our work broadens the horizon of study on dielectric materials through proton doping and may also provide an approach that enables the utilization of dielectric materials in energy conversion applications. [ABSTRACT FROM AUTHOR]

Ultrasound-stimulated piezo-electrocatalysis has been studied for a period; however, the mechanism is still unclear mainly due to the coexistence with other multiple effects like sonocatalysis, which was usually ignored. In this work, with the non-piezoelectric H2Ti3O7 nanowires following the same experimental process in piezo-electrocatalysis, the sonocatalytic reduction performance of CO2 is investigated. By applying vibration under the excitation of ultrasound with various frequencies and powers, it is found that CO is the ultimate product with a selectivity of 100%, and the optimal CO yield of 8.3 μmol g−1 h−1 is achieved with the addition of sacrificial agents. The H2Ti3O7 catalysts are also found to present a good recycling utilization ability. This work indicates that the sonocatalysis effect may exist in the piezo-electrocatalytic process using the ultrasonic excitation, which is suggested to be taken into consideration when exploring the mechanism of piezo-electrocatalysis in the future. [ABSTRACT FROM AUTHOR]

The intrinsic flexoelectric effect observed in oxide materials often falls below the desired threshold for practical applications. In this work, we demonstrate proton doping in insulating rutile TiO2 crystal as an effective approach to significantly increase flexoelectricity by more than two orders of magnitude. We attribute the noteworthy enhancement of flexoelectricity to the dual impact of proton doping in oxide materials. First, proton doping serves to induce the presence of charge carriers, resulting in the generation of flexoelectric currents. Second, proton doping induces expansion and distortion of the lattice structure, leading to an amplified flexoelectric field when the crystal experiences a strain gradient. The formation of O–H bonding in TiO2 crystal provides another route to break centrosymmetry according to lattice distortion of the TiO2 lattice, resulting in a larger flexoelectric field. In addition, the introduction of proton doping in TiO2 single crystals leads to a substantial increase in photocurrent by effectively flattening the interfacial Schottky junction. This phenomenon results in a three-order of magnitude enhancement of the photocurrent. Our work broadens the horizon of study on dielectric materials through proton doping and may also provide an approach that enables the utilization of dielectric materials in energy conversion applications. [ABSTRACT FROM AUTHOR]