Excellent catalytic performance of molten-salt-synthesized Bi0.5Na0.5TiO3 nanorods by the piezo-phototronic coupling effect

Abstract

The coupling between piezoelectricity and photoexcitation has recently been emerged as an effective strategy to improve the catalytic performance of semiconductors. Lead-free Bi 0.5 Na 0.5 TiO 3 (BNT) is a promising system for effective piezo-photocatalysis owing to its favorable piezoelectricity, photoexcited response, and electrical conductivity. In this work, one-dimensional BNT nanorods prepared by a high-temperature molten-salt method were developed for piezo-photocatalysis applications for the first time, which exhibited excellent catalytic activity. The degradation efficiency of RhB solution (initial concentration C 0 = 5 mg/L) in the presence of BNT nanorods reached 95% in 30 min, leading to a high first-order rate constant k of 0.094 min −1 . For reveal the underlying mechanisms, the piezoresponse characterization, piezoelectric potential simulation, band diagram analysis, and photoelectrochemical measurements were carried out, and the BNT nanospheres synthesized by hydrothermal method were simultaneously studied for comparison. A higher piezoelectric coefficient d 33 * of 200 pm/V and a larger potential output under pressure were achieved in the BNT nanorods. The BNT nanorods also displayed the narrower band gap, stronger photocurrent response, and lower charge transfer resistance. These merits enabled the BNT nanorods to exhibit strong piezo-photocatalytic activity. Moreover, it was found that the BNT nanorods showed better piezo-photocatalytic activity for cationic dyes (RhB and MB) than anionic dyes (MO). For RhB, MB, and MO solutions with C 0 of 10 mg/L, k values of 0.041, 0.075, and 0.013 min −1 were achieved, respectively. • Highly-crystalline, tough, and durable BNT nanorods were prepared by a molten-salt method. • The BNT nanorods show large piezoelectric potential and effective separation of photogenerated carriers. • The k value reaches 0.094 min −1 for RhB degradation via the BNT nanorods and piezo-phototronic coupling effect.