A catalyst device for use with battery cells to recombine oxygen and hydrogen gas and thereby improve the performance and life of such cells. The catalyst device has the ability to filter out catalyst poisons and control the temperature of the recombination reactions. A container houses the catalyst within a chamber. A catalyst poison filter is provided in the chamber with the catalyst. The movement of gas and vapor to and from the chamber is controlled by a microporous section of the device. The pore size is chosen to allow gas and vapor to pass, but not liquids, and to also prevent a flame from passing through. Within these parameters the pore size can also be chosen to control and or limit the amount of gas that can pass through to the catalyst in a given time period. Preferably, the microporous section is formed as a disc that seals an opening in the chamber. The filter material is then placed as a layer between the catalyst and the opening such that the poison in the gas must pass through the filter material before reaching the catalyst.