[22p-E204-1~13] 6.3 Oxide electronics

▼ [22p-E204-9] Reversible rapid protonation of WO₃ films in non-acid solution

〇Zhiping Bian¹, Jiangtao Zhao¹, Heng Cao¹, Yongqi Dong^1,2, Zhenlin Luo¹ (1.NSRL, USTC, 2.SIAT, CAS)

Keywords:protonation, non-acid, WO3

Protonation, an effective way to tune the properties of transition metal oxide (TMO) thin films, has been long-awaited to be performed safely and without external energy input. Recently, metal-acid-TMO has been reported to be an effective approach for protonation, but the requirement of acid limits its application.^[1-3] In this work, the reversible and rapid protonation of WO₃ in NaOH (aq.) | Al (s) | WO₃ (s) is revealed by structural and electrical measurements.^[4] Accompanied by the structural phase transition identified by in-situ X-ray diffraction measurements, the electrical resistance of the WO₃ film is found to be able to change by five orders of magnitude. A significant electrical response of touching, 8-fold in amplitude and 3 seconds in a cycle, can be achieved in the low resistance state. These reactions are reversible at room temperature. This study unambiguously proves that the protonation-driven dynamic phase transition of WO₃ in metal-solution-WO₃ systems could occur not only in acid solutions but also in some non-acid environments. Unlike the monotonic increase of resistance revealed during H_δWO₃ to WO₃ transition, an intriguing non-monotonic evolution was found for crystal lattice parameter c, indicating that the mechanism of WO₃ protonation involves a series of metastable states, more comprehensive and reasonable. This work sheds light on the potential applications of metal-solution-TMO protonation in touching sensors, circuits survey and information storage.
[1] Y. Chen et al., Nat. Commun. 9, 818 (2018).
[2] L. Xie et al., J. Am. Chem. Soc. 142, 4136-4140 (2020).
[3] X. Yao et al., Nat. Commun. 11, 3134 (2020).
[4] Z. Bian et al., ACS Appl. Mater. Interfaces 13, 13419 (2021).