Infrared Excited Proton Conductivity in BaZr_0.8Y_0.2O_3-δ

Proton-conducting oxides, such as acceptor-doped BaZrO₃, exhibit excellent proton conductivity at intermediate temperature, and can be applied in proton ceramic electrochemical cells. Modulating the atomic vibration, including lattice and localized vibration, has been recently suggested as an emerging approach to promote the ion transport of materials. However, such studies on proton-conducting oxides are still limited. The frequency of infrared light covers the O-H vibration and lattice phonon modes in doped BaZrO₃, thus can potentially promote proton transport. In this work, we show an enhancement in bulk and grain boundary (GB) proton conductivities of BaZr_0.8Y_0.2O_3-δ (BZY20), upon excitation using a 140-mW continuous-wave mid-infrared (MIR) light. While the operating temperature is maintained at 160 °C, a reversible enhancement in bulk and GB proton conductivities of 28.6% and 41.2% upon MIR irradiation was observed, respectively. The enhancement in proton conductivity is power-dependent. Narrowband MIR irradiation indicates that the enhancement effect is greater at the wavelength at the resonant frequency of O–H stretching vibration. Infrared light helps to reveal the role of atomic vibration on proton conduction, thereby facilitate improving the proton conductivity in oxides at lower temperatures.