Surface engineered metal nitrides for genuine nitrogen Reduction – SUNRed

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Ammonia is an essential basic chemical indispensable for today’s society and modern agriculture. Interest in the electrochemical ammonia synthesis has recently grown tremendously in light of climate change and the use of ammonia to form carbon free, energy-dense, liquid hydrogen carriers and future fuels. The project “Surface engineered metal Nitrides for genuine nitrogen Reduction (SuNRed)” targets the demonstration of genuine (photo)electrochemical ammonia synthesis from elemental nitrogen on transition metal nitrides and their oxynitrides (partly under contribution of carbon nitrides) which are improved in performance (efficiency and/or selectivity) by surface engineering. The consortium from the Carl von Ossietzky University Oldenburg, the German Aerospace Center (DLR), the Ruhr University Bochum and a colleague from Tyndall National Institute in Ireland as Mercator fellow combines in depth expertise from the fields of synthesis of surface engineered nanostructured materials, thin film catalysts, and porous materials with competencies in electrochemical and photoelectrochemical evaluation including theoretical-chemical calculations of the surface reactions.The electrocatalytic nitrogen reduction reaction on nitrides most likely proceeds via the heterogenous Mars-van-Krevelen (MvK) mechanism, overcoming the drawback of nitrogen adsorption as the initial mechanistic step that limits the performance of other catalysts. In the MvK mechanism, formation and filling of nitrogen vacancies play a crucial role. The role of these vacancies and their engineering will be the focus of SUNRed, whereby we exploit nitrogen vacancies to enhance the activity and selectivity of transition metal nitrides. We therefore hypothesize that surface engineering and heteroatom doping can tune the concentration and coordination environment of nitrogen vacancies, which can be used to control the fundamental mechanistic steps in the nitrogen reduction reaction and promote selective transition to ammonia rather than undesired byproducts.Using the knowledge gained from facet-controlled model catalyst surfaces, active site modification by insertion of vacancies and heteroatom doping in transition metal nitride model catalysts will enable us to systematically study and understand structure-property-relationship of these materials. Investigations of application-related catalyst morphologies (porous structures, nanoparticles) and complementary theoretical insights, realised by the Mercator-Fellow, through the computational description of nitrogen vacancies, stability and nitrogen reduction reaction kinetics in the MvK mechanism will deliver in a comprehensive picture of the nitrogen reduction reaction activity of transition metal nitrides.