(Invited) Electrocatalytic Ammonia Splitting for Hydrogen Generation

Abstract

Much of the global effort toward producing solar fuels has involved splitting water to obtain molecular hydrogen. Unfortunately, hydrogen gas has a relatively low energy-per-volume, and extreme cryogenic temperature and pressure is needed to bring hydrogen to a condensed state. An interesting choice for a hydrogen storage medium that circumvents these setbacks is ammonia. Synthesis of ammonia (largely via the Haber-Bosch process) is already the second-largest chemical industrial process in the world, and as a result the infrastructure for ammonia storage and transport already exists. In the first part of this talk, I will introduce a new method of storing liquid ammonia at room temperature and atmospheric pressure by combing it with certain ammonium salts to form binary solutions. Preliminary electrochemical investigations of this interesting solvent system will be introduced, including electrolysis to generate hydrogen and nitrogen. The ammonia oxidation overpotential ultimately limits the efficiency of ammonia electrolysis. The second part of this talk will discuss electrocatalytic measurements of homogeneous electrocatalysts, including the transition metal complex, [Ru(tpy)(dmabpy)NH3]2+ (tpy = 2,2′:6′,2′′-terpyridine, dmabpy = 4,4'-dimethylamino-2,2'-bipyridine), in non-aqueous solvent systems with the aim of lowering the overpotential. Recent results at uncovering the mechanism of ammonia oxidation with this ruthenium catalyst will be presented and used to model and interpret the cyclic voltammetric response of electrocatalysis.