Electrodes Materials for Ammonia Oxidation to Produce Hydrogen and Nitrogen.

The past three decades have seen an explosion of research on new technologies to produce green energy by investigating new systems that can reduce coal, oil, and natural gas usage. In particular, the European Union imposes Carbon Neutrality by 2050, which requires an ecological transition to renewable sources, electric mobility, a circular economy, and energy storage. Two key points of the energy transition are reducing carbon dioxide emissions into the atmosphere and using green hydrogen as an energy vector. Using hydrogen as an energy carrier allows for overcoming the intrinsic limits of renewable energy. When the electricity produced by the renewable source exceeds the demand, the surplus can be used to carry out water electrolysis and produce hydrogen. And when demand exceeds supply, hydrogen can be used to produce electricity in fuel cells. However, there are several problems with the direct use of hydrogen. First of all, hydrogen does not exist in nature in molecular form. Secondly, it is difficult to store or transport due to its low volumetric energy density and small molecular size. Treating pollutants in wastewater coupled with energy recovery is an attractive solution to reduce environmental pollution and provide alternative energy sources simultaneously. Hydrogen may be generated from hydrogenated pollutants in water through photocatalysis, and the overall reaction is thermodynamically more favorite than water splitting for hydrogen. Within this context, the project aims to study the electrolysis of polluting molecules in water, such as nitrogenated molecules, using ammonia as a model molecule. Electrolysis, which separates water molecules into oxygen and hydrogen, is a clean but energy-intensive process, which is convenient only on occasions when there is a lot of energy available and little need. So the aim is to couple to the cathodic reaction that produce H2 from water in an electrolyzer an anodic oxidation that lallows for the detoxification of an industrial or civil effluent. To help in the oxidation process of polluted molecule oxidation also a "sono-photo-electrocatalysis” has been adopted. We started by creating a setup consisting of an electrolytic cell and three electrodes: the working electrode, the counter electrode, and the reference electrode. The reference electrode is Hg/HgO (+0.092V versus SHE), and the counter electrode was made of platinum foil. The starting material is Platinum, then graphite and different metals were tested: Nickel, Titanium, Lead Oxide, Copper, and 304 stainless steel. The electrolytic solutions were 1M KOH, then 5M and 0.1M, respectively. For each material, numerous CVs were made in a specific range of potential to determine the possible oxidation of ammonia. The materials that gave positive feedback were Platinum and Copper. Copper is an interesting material from an industrial perspective since it is cheaper than Platinum (it is not a precious metal) and much more widespread.