Mid-infrared light resonance-enhanced proton conductivity in ceramics

Ionic transport in solids is critical for energy applications in batteries and fuel cells. To improve ionic transport, an emerging approach is the selective excitation of atomic vibrations related to the mobile ions. However, there is limited direct experimental evidence demonstrating enhanced macroscopic ionic conductivity through this approach. Here, we used a 140-mW continuous-wave mid-infrared (MIR) light to excite the O–H stretch vibration in proton-conducting yttrium-doped barium zirconate. We observed reversible enhancement of 28.6% in bulk, and 41.2% in grain boundary proton conductivities, controlled by MIR irradiation. Decreases in the activation energy and prefactor for bulk proton conduction suggest possible reduction in activation entropy and attempt frequency of proton hopping. We rationalize the enhancement by modelling the excitation of vibrational states in the potential energy surface of the proton. Our findings highlight MIR irradiation as a power-saving strategy to optimize the performance and operation cost of solid-state electrochemical devices by selective modulation of the vibrational properties.