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Advanced oxidation processes including piezocatalysis and photocatalysis are considered as promising strategies for environmental remediation. More efforts have been made to clarify the factors that can improve the catalytic efficiency in piezocatalysis. Diphasic Ba1−xCaxTiO3 piezoelectric materials near a solubility limit have been found to exhibit potential for piezoelectric performance far beyond their corresponding single-phasic materials. It is interesting to explore how phase structures (single phase and diphase) will influence the catalytic performance of nanoscale piezoelectric materials. In this study, Ba1−xCaxTiO3 nanowires were used as representative materials to explore the influence of phase structures on catalytic performance. It is found that when x = 0.2 (near the solubility limit), the Ba1−xCaxTiO3 nanowires exhibit better piezocatalytic and photocatalytic performance. This can be ascribed to higher spontaneous polarization induced by the interaction of a ferroelectric tetragonal Ba-rich phase and a normal dielectric orthorhombic Ca-rich phase and band alignment of Ba-rich and Ca-rich phases, which can both effectively enhance charge carrier separation rates. In addition, with the simultaneous assistance of ultrasonic vibration and ultra-violet light, there is a coupling catalytic effect of Ba1−xCaxTiO3 nanowires, with a rate constant kobs of 71% higher than the simple sum-up of the rate constants of piezocatalytic and photocatalytic reactions. The increasing piezo-/photocatalytic degradation efficiency is mainly attributed to increased free charge carrier concentrations (thermally-excited and photo-induced charge carriers) and a strong piezoelectric field induced by the piezoelectric effect, which is beneficial for the separation of free charge carriers. We believe that this work provides mechanistic insights into how phase structures affect catalytic performance and a novel route to furnish environmentally-friendly catalysts that can efficiently utilize multiple energy sources.

As a new catalytic effect, piezocatalysis has attracted much attention due to its ability to degrade organic pollutants under mechanical vibration. However, improving the efficiency of piezocatalysis still remains a challenge. Here, we report an efficient route to enhance the piezocatalytic performance of BaTiO3 by surface modification with Ag nanoparticles (NPs). The Ag NPs were deposited by a facile in situ photo-reduction method. The piezocatalytic efficiency of the as-prepared samples was investigated by monitoring the degradation of methyl orange (MO) under ultrasonic vibration in the dark. The results indicate that the Ag loaded BaTiO3 particles show greatly enhanced piezocatalytic activity for degradation of MO molecules. A suitable amount of Ag deposition gives the highest piezocatalytic activity, while a higher Ag loading leads to reduced piezocatalytic activity. The degradation of MO and the possible by-products as well as the active radical species generated in the piezocatalytic system were investigated systematically. Based on the experimental results, a mechanism was proposed to explain the enhancement effect of Ag NPs on the piezocatalytic performance of BaTiO3. The strategy presented here provides a promising route towards the development of high-efficiency piezocatalysts for actual applications.