Catalysts for the Electrooxidation Ammonia Reaction: Analysis with different NH_4OH concentrations

Abstract

Fuel cells are electrochemical devices that convert directly chemical energy in electrical energy. The search for a clean, economical and sustainable fuel with high density energy has led to the growing consideration of fuels based on nitrogen, such as ammonia.
Ammonia is an excellent source of hydrogen in its liquid form. Liquid ammonia can be stored in large tanks at room temperature and is safer than propane and as safe as gasoline. More than 200 million tons of ammonia are produced each year and distributed globally via pipelines, tankers & trucks, making ammonia readily available and cheap.
Platinum (Pt) is the catalyst par excellence in fuel cells due to its high electroactivity. However, this precious metal is not abundant in nature and its cost is high, which causes the development of fuel cells is not commercially attractive (Cespedes et al., 2016). The US Department of Energy (DOE) has estimated that to make the mass use of the cells the price should be reduced to about 40 USD/kW in 80 kW systems (Qaseem et al., 2016). To reduce the cost associated with the use of Pt are synthesized nanostructured catalysts, thereby greatly increasing the surface area specific and the number of atoms found on the surface of the catalyst. Additionally, the Pt is usually combined with other elements to enhance the catalytic activity thereof (Zhong et al., 2013). The catalytic activity of the materials to be prepared strongly depends on the method of synthesis to be implemented, since it can control the size, shape and composition of the catalytic nanoparticles. In recent years reproducible synthetic methods have been developed. In this way, nanoparticles can be obtained by combining different metals in alloy shape, core-shell, etc.
Electrocatalysts known as the aforementioned Pt, in its commercial form Pt-ETEK to different concentrations of ammonia, and bimetalic of the PtM type (with M = Ni, Ru) dispersed on a high-surface conductive support were evaluated using synthetic methods that involve the chemical reduction of the metallic precursors for the catalyst in question.