Study of nickel-molybdenum alloy based catalysts for hydrogen evolution reaction and oxygen evolution reaction in a anion exchange membrane electrolyzer

The hydrogen economy is becoming more feasible in recent years due to technological progresses in materials development. Such improvements have allowed a reduction in manufactory cost from year to year, making hydrogen competitive with the solutions currently available on the market. To this regard, the best way to produce H2 is by water electrolysis, that is one of the most abundant and renewable sources of hydrogen present in nature. Unfortunately, some problems remain due to the use of critical raw materials employed for the fabrication of the catalysts, like Platinum Group Metal (PGM) and the membrane stability and permeability. In order to make these technologies available to a large market, many efforts have been made to limit or eliminate precious metals from the catalysts. Here we report PGM free catalysts for anion exchange membrane electrolyzer based on Nickel-Molybdenum alloys and iron oxide-hydroxide: MoNi4:MoOx-3/Nifoam for the cathode and Fe-MoNi4:MoOx-3/Nifoam for the anode. These materials have some interesting advantages; firstly a facile hydrothermal synthesis, this procedure requires only the metal salts and water, representing also a "green" alternative with respect other pathways, once the mixed oxide are grown on the Nifoam surface , thermal annealing under reducing atmosphere leads to the formation of MoNi4:MoOx-3/Nifoam. An iron oxide-hydroxide anode can be prepared by simply dipping the lamina of MoNi4:MoOx-3/Nifoam in a solution of FeCl3. Tests carried out in a complete AEM electrolyzer demonstrate improved performances, showing very good stability with a current loading of 500 mA/cm2 for 1 day at 60°C, keeping the potential around 1.8 V. Further improvements are aimed to bring the current density to 1 A/cm2 maintaining the same cell potential.