This paper presents the report on the piezophotocatalysis of single-crystal rhombohedral ZnSnO 3 nanowires. An essential feature of this study was the close coupling of the functions of piezophototronics (semiconductors, piezoelectricity, and photonics) and photocatalysis for achieving synergistic catalytic performance. Vertically aligned lead-free noncentrosymmetric high purity ZnSnO 3 nanowires (LiNbO 3 -type, R3c) were fabricated using a two-step hydrothermal reaction. The piezophototronic effect was demonstrated to substantially enhance the photocatalytic activity (by approximately 27%) by modulating the piezopotentials across the ZnSnO 3 nanowires. The enhancement was attributed to reduced recombination of photogenerated electron-hole pairs and enhanced mobility of these pairs resulting from the energy band distortion caused by applied stresses.

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This paper reports a facile fabrication method for robust and separated polycrystalline Ta 4 N 5 nanocolumn arrays on a FTO/glass substrate that involves using reactive sputtering, which provides an alternative approach to fabricating nitrides without using caustic NH 3 gases. The bandgap of Ta 4 N 5 nanocolumns made at 600 • C was observed to be approximately 2.5 eV. The excellent photodegradation performance was demonstrated in an environment with a pH of 10, in which approximately 80% of methylene blue (5 ppm) was photodegraded in 90 min. The incident photon-to-current efficiency of the 600 • C sample showed equivalent or superior characteristics compared with the Ta 3 N 5 and IrO 2 /Ta 3 N 5 thin films reported in the literature. The photoelectrochemical current measurement also demonstrated the stability of the sample. These features suggest that Ta Photodecomposition of organic pollutants that entails using longlasting solar power is one of the most sustainable applications of photocatalysis, 1 in addition to photocatalytic water splitting for hydrogen (H 2 ) production.2,3 Although various semiconductors have been proposed for such applications, most of these semiconductors exhibited various problems and limitations; for example, PbS and CdS 4,5 are toxic and easily photocorroded in a solution; ZnO is photocorrosive 6 and difficult to synthesize using solution-based processes because of its low solubility in water;7 Fe 2 O 3 , SnO 2 , and WO 3 require additional power to trigger harvesting of H 2 because of the unsuitable conduction band edges. 8 TiO 2 has been the most studied photocatalyst, 9,10 but exhibits excellent photocatalytic activity only under ultraviolet (UV) irradiation because of its wide bandgap (approximately 3.2 eV for anatase and 3.0 eV for rutile 9 ). A desirable photocatalytic process should occur in the visible light range, which comprises the prevailing portion (approximately 43%) of the solar spectrum. 3,11Tantalum nitride, existing in various stable and metastable phases, 12,13 represents another promising material system because it exhibits various favorable properties. The microstructure, as well as the mechanical and electrical properties, can be modulated within a wide range, depending on the deposition techniques 14 and the stoichiometry of nitrogen. 19,[24][25][26] and photodecomposition of organic pollutants. In particular, Ta 3 N 5 has received considerable attention because of its advantageous band structure (E g ∼ = 1.5 eV-2.1 eV).19,27-30 Studies have typically synthesized Ta 3 N 5 by using a two-step approach; Ta 2 O 5 was first grown, and subsequent nitridation was employed to obtain Ta 3 N 5 in a moisturized NH 3 atmosphere. 25,[30][31][32][33] This method typically exhibited the poor control of film thickness and structural discontinuities during oxidation and nitridation. 31 Consequently, high defect densities of Ta 3 N 5 were attained, thus compensating the photoelectrochemical (PEC) performance. 34 In addition, the chemical and functional instability of Ta 3 N 5...

This study examined the fabrication of high‐density rhombohedral ZnSnO3 nanowire arrays on fluorine‐doped SnO2 (FTO) substrates through single‐step hydrothermal synthesis and their synergistic piezo‐related performance. The band gap (approximately 3.7 eV) and valence band (Ev) position (approximately 2.7 eV below the Fermi energy of Au [approximately −4.9 eV]) of the arrays were obtained using ultraviolet‐visible (UV‐Vis) spectrometry and UV photoelectron spectroscopy, respectively. An energy band diagram was obtained, revealing the favorable band positions of the samples for photodegradation and water splitting. Reliable and superior piezophotodegradation capability with a degradation rate constant of approximately 17.6 × 10−3 min−1 was also observed. Holes and •OH were predominant for the degradation mechanism, as determined by scavenger studies. Moreover, the samples exhibited favorable piezophotoelectrochemical (PPEC) performance, which was validated by the obtained applied bias photon‐to‐current efficiency. The stress‐induced photocurrent density observed in a PPEC reaction was more than twice that observed in a photoelectrochemical reaction. Both piezophotodegradation and PPEC reactions were attributable to the inhibition of electron‐hole pair recombination because of the excellent alignment of the nanowires, piezopotential buildup, and band bending of the ZnSnO3 nanowires. Our results indicate a positive effect of piezoelectricity on the piezo‐related applications of the sample.

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