Hydrogen production from wastewater: study of electrode materials for ammonia oxidation

During the last three decades, there has been an exponential growth in the research of new technologies able to generate green energy by reducing the consumption of fossil fuels. In particular, the imposition of Carbon Neutrality by 2050 by the European Union requires an ecological transition to renewable sources, electric mobility, a circular economy, and energy storage. Hydrogen has been identified as a potential alternative energy carrier. The chemical energy stored in hydrogen can be converted into useful energy in a number of ways, electric energy by a fuel cell, mechanical energy by a hydrogen combustion engine, and heat energy by a hydrogen water heater. To date, hydrogen-based technologies show critical issues that require further investigation. Among them, the main difficulties are associated with the costs of production, storage and safe transportation of hydrogen [1]. The degradation of pollutants in wastewater coupled with the production of energy by ammonia splitting is an attractive and interesting method that allows to reduce environmental pollution and simultaneously provide alternative energy sources. Within this context, the present project aims to study the electrolysis of nitrogen-rich polluting molecules in water. The preliminary results summarized in the present work regard the use of ammonia as a model molecule. In general, electrolysis, which separates water molecules into oxygen and hydrogen, is a clean but energy-intensive process. Here, we combine the cathodic reaction that produce H 2 from water with an anodic oxidation that allows for the detoxification of an industrial or civil effluent by screening suitable electrodes. The reaction was carried out in the absence and in the presence of ultrasounds to enhance energetically the oxidation process and at the same time maintain clean the electrode’s surface. Different electrodes have been tested, such as graphite and different metals (platinum, nickel, titanium, lead oxide, copper, palladium) and 304 stainless steel [2]. 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.