Thickness and Humidity on Proton Conductivity in MOF-508 Thin Film by Twin-Zinc-Source Method

Abstract

To achieve structurally stable and high proton conductive materials, preferably under ambient humidity and pressure, the well-controlled thickness and conductivity of the MOF thin films represent an effective approach. Electrodes are the most important part of fuel cells; proton conducting materials are often used for electrodes, but today high proton conducting materials are expensive and use harsh conditions. Therefore, the goal of researchers is the pursuit of stable structure high proton conductive materials. We prepared well controlled thickness and conductive MOF-508a thin films on a Zn substrate by the “twin zinc source” method, which is very rare in conventional proton conductive materials. The results show that when the thickness of the MOF-508a/Zn thin film was at its minimum (16 µm), the resistivity and proton conductivity reached 2.5 × 103 Ω cm and 4 × 10−4 S cm−1, respectively. The MOF-508b/Zn thin film can absorb water molecules in a high humidity atmosphere and the conductivity decreases significantly with increasing humidity. When the film was put into the atmosphere with a relative humidity of 85%, the resistivity reached 200 Ω cm significantly. This work provides a simple, low cost, and environmentally friendly strategy for fabricating high proton conducting MOF films by exploring the “twin-zinc-source” method, which is critically important for PEMFC. It is believed that higher conductivity MOF films can be obtained with further modifications, indicating the potential of such films as humidity detectors.