Incorporating Strong Polarity Minerals of Tourmaline with Semiconductor Titania to Improve the Photosplitting of Water

Abstract

This paper describes a method for increasing the quantum efficiency in the photosplitting of water by integrating the Degussa P25 titania photocatalyst with a polar mineral tourmaline having surface electrical fields due to the pyroelectric effect. The amount of hydrogen produced from the photosplitting of water increased considerably with a tourmaline-integrated P25 titania photocatalyst compared to that with P25 titania in systems containing pure water as well as solutions of different pH values. It is proposed that the enhancement in the photocatalytic performance is due to a reduction in the Schottky barrier for electrons to migrate to the surface of the semiconductor. The surface electric fields of tourmaline lower the barrier by reducing the band bending in the space charge layer and increasing the chemical potential (E F) of the electrons in titania. The increase in the amount of hydrogen produced at a lower pH is attributed to the decrease in the overpotential of the hydrogen evolution reaction at lower pH values. In contrast to photocatalytic reduction, tourmaline has very little effect on titania for the photocatalytic oxidation of acetaldehyde. It is proposed that the surface electric fields present on tourmaline crystals reduce the band bending in the semiconductor and thus decrease the oxidation potential of the photogenerated holes. The results have important implications for enhancing the photocatalytic activity of titania for environmental remediation, increasing the quantum efficiency in photovoltaic (PV) solar cells, and other photoassisted processes.

Incorporating Strong Polarity Minerals of Tourmaline with Carbon Nanotubes to Improve the Electrical and Electromagnetic Interference Shielding Properties

“…22,23 Electric fields on the order of 10 6 −10 7 V/m exist on the surface of micrometer-sized tourmaline. 21 The work presented here focuses on enhancing the quantum efficiency, that is, the electron transition between CNTs by integrating CNTs with the TPs having spontaneous surface electric fields into a polyurethane (PU) matrix by in situ polymerization. The change in the electrical properties of MWNT-contained polyurethane composite (PU/MWNT) by adding different loadings of TPs is investigated via two sets of experiments: (i) conductivity and (ii) EMI shielding effectiveness.…”

Investigating the synergistic effects in tourmaline/TiO2-based heterogeneous photocatalysis: Underlying mechanism insights

“…Tourmaline has fascinating properties analogous to ferroelectrics and exhibits a unique behavior with spontaneous and permanent poles, different from any other minerals in natural geologic environment. Internal dipolar field presents in the vicinity of the surface of micron-sized tourmaline with an intensity of 10 6 -10 7 V/m, which arises from the spontaneous polarization due to lack of symmetric center, mirror plane, or rotation axes oriented perpendicular to the c axis in the crystal [19]. In this sense, incorporation of TiO 2 to a polarizable mineral, tourmaline, can be envisioned to meet the challenges of both quantum efficiency and nanoparticles aggregation in TiO 2 -based photocatalysis.…”

“…However, the limited assessments concerned to date [20][21][22] mainly concentrated on parameter optimization and kinetic analysis of the degradation process. Only Yeredla and Xu [19] attempted to explain the mechanism for the enhanced activity in photosplitting of water at the band bending level; nevertheless, the results obtained were highly speculative for deficiency in supportive data and characterization means available. As such, current researches are often subject to the poor interpretation for the synergistic effect as well as the ambiguous role of tourmaline, the relevant exploration with a deep investigation into the mechanism and experimental parameters is still insufficient.…”

The effect of tourmaline additives in TiO2 photoanode for high-efficiency dye sensitized solar cells

“…Since tourmaline belongs to the trigonal or rhombohedral lattice crystal structures with the space group R3m, tourmaline has unique electrical properties, such as spontaneous polarization, pyroelectricity, piezoelectricity, and ability to generate a feeble current around 0.06 mA [4][5][6]. Tourmaline has been studied for many applications, such as photosplitting of water [6], photocatalyst [7], electrical/electromagnetic interference shielding [8], and bio-cathode microbial fuel cell [9]. However, there were no reports on the DSSCs application with tourmaline.…”