Content description of the project
The project aims to improve ammonia synthesis as one of the most energy‐hungry reactions, using plasmon‐induced nanoparticle photocatalysts. Such an approach (1) harnesses solar energy, (2) uses less energy altogether (change in reaction mechanism) and (3) substitutes H2 with water as a feedstock. The ability to produce NH3 from readily available feedstocks – H2 and N2 – has made the population explosion and technological boom of the 20th century possible. Historically, ammonia had been produced with dry distillation of vegetable and animal products, from nitrates and ammonium salts, which was expensive and of limited scale. Nowadays, 235 Mt of ammonia is produced annually by the century‐old Haber‐Bosch process, consuming 1.8 % of global energy and producing 500 Mt of CO2 emissions. More than 88 % of NH3 finds use as a fertilizer, literally feeding the world. Additionally, it is used as an important precursor in the chemical industry (production of urea, phenols, amino acids, acrylonitrile, hydrazine, explosives etc.), as a cleaning and antimicrobial agent, and in niche applications (lifting gas, woodworking, textile treatment, stimulant). NH3 cannot be replaced. Virtually all NH3 production in the EU uses fossil‐based natural gas as a feedstock for H2. Although this is less energetically wasteful that the old process of producing H2 from coal, it is still not sustainable. Utilizing renewable electricity sources (solar, wind) to produce H2 from water hydrolysis would increase electricity consumption and cannot be a sustainable solution. Moreover, this does not address the underlying problem: the reaction between H2 and N2 still requires extremely high temperatures and pressure. The Haber‐Bosch process has remained fundamentally the same since its discovery in 1910. Traditional catalysts are iron‐based, have a complicated composition and are produced by an elaborate procedure (Ca, K, Al, Si promoted iron oxide magnetites). Second‐generation catalysts are ruthenium‐based, supported on oxides (MgO, Al2O3), plagued by Ru being an expensive critical raw material. Moreover, the old process is thermocatalytic, requiring high temperatures (400–500 °C) and pressures (80–300 atm) because of two opposing constraints. Thermodynamically favoured low temperatures are kinetically useless (high activation barrier); at high temperatures the equilibrium shifts away from NH3 (Le Chatelier’s principle). Thermocatalytic processes, perfected for the past century, have little room for improvement. As climate change calls for optimization of the most energy‐hungry production processes, new catalytic approaches are needed. Plasmonic photocatalysis is a potential alternative if we can optimize the catalyst material, particle shape/size, irradiation, conditions. These can now be predicted, as the available computing power has reached levels that allow atomistic simulations of chemical reactions, kinetic modelling of catalysts and dynamic descriptions of reactors. This new catalytic route will be unlocked with a unique approach. Instead of trial‐and‐error catalyst/conditions testing, we will use multiscale modelling to understand, describe, predict and simulate the effect of nanoparticle shape/size, core‐shell structures, and conditions/irradiation on Au/Ru catalysts. The overarching objective of the project is to establish a new paradigm of plasmonic catalysis by providing fundamental understanding, which will be used for a guided screening of prospective catalyst materials for ammonia production through first‐principles machine‐learning assisted multiscale modelling. Understanding of plasmonic photocatalysis for ammonia synthesis is pivotal for addressing issues with a great projected impact on our environment, health and prosperity as individuals and as a society.
