Surface engineered metal nitrides for genuine nitrogen Reduction – SUNRed

氨是当今社会和现代农业不可缺少的重要基础化学品。鉴于气候变化和利用氨形成无碳、高能量、液氢载体和未来燃料，近年来对电化学氨合成的兴趣急剧增长。“表面工程金属氮化物用于真正的氮还原（SuNRed）”项目的目标是演示从元素氮到过渡金属氮化物及其氧氮化物（部分由碳氮化物贡献）的真正（照片）电化学氨合成，这些化合物通过表面工程提高了性能（效率和/或选择性）。来自奥尔登堡卡尔·冯·奥西茨基大学、德国航空航天中心（DLR）、波洪鲁尔大学和爱尔兰廷德尔国家研究所的一位同事作为墨卡托研究员，联合了来自表面工程纳米结构材料、薄膜催化剂和多孔材料合成领域的深入专业知识，并在电化学和光电化学评估方面具有能力，包括表面反应的理论化学计算。氮化物上的电催化氮还原反应最有可能通过异相Mars-van-Krevelen （MvK）机制进行，克服了氮吸附作为限制其他催化剂性能的初始机制步骤的缺点。在MvK机制中，氮空位的形成和填充起着至关重要的作用。这些空位的作用及其工程将是SUNRed的重点，因此我们利用氮空位来提高过渡金属氮化物的活性和选择性。因此，我们假设表面工程和杂原子掺杂可以调节氮空位的浓度和配位环境，这可以用来控制氮还原反应的基本机制步骤，并促进选择性过渡到氨而不是不想要的副产物。利用从面控模型催化剂表面获得的知识，通过插入空位和杂原子掺杂对过渡金属氮化物模型催化剂的活性位点进行修饰，将使我们能够系统地研究和理解这些材料的结构-性能关系。墨卡托研究员通过对MvK机制中氮空位、稳定性和氮还原反应动力学的计算描述，研究了与应用相关的催化剂形态（多孔结构、纳米颗粒）和互补的理论见解，将全面了解过渡金属氮化物的氮还原反应活性。

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.