Gas-Diffusion Composite Electrode Containing Zeolite and Carbon in the Gas-Diffusion Layer

A composite gas-diffusion electrode containing carbon and zeolite, for rechargeable metal-air batteries was developed. To ensure the uniform distribution of the clinoptiolite particles in the carbon matrix, as well as mechanical stability of the gas-diffusion layer high-energy milling (5000 rpm for 1 min) and subsequent pressing of the mixture (300 kg.cm⁻² at 280 °C) were applied. By partially replacing the teflonized carbon black in the gas-diffusion layer with clinoptiolite the necessary hydrophobicity could be attained while maintaining the high gas permeability of the zeolite material. The teflonized carbon black: zeolite mass ratio was optimized in terms of the mechanical stability of the electrode and its electrochemical performance. The catalytic layer comprised a bimetallic catalyst consisting of Ag and γ-MnO₂ in a 1:1 mass ratio. The morphology of the catalytic layer, as well as the pore size in the gas-diffusion layer, were studied using scanning electron microscopy and the Brunnauer-Emmett-Teller method. The determined pore size below 10 nm implies mainly the Knudsen diffusion through the gas-diffusion layer. In the preliminary durability tests high mechanical, chemical, and electrochemical stability (more than 750 cycles) was obtained for the newly developed composite gas-diffusion electrode.