Content description of the project
Thermocatalytic nitrogen activation, which has been known for more than a century, is plagued by high energy demands and using H2 as a feedstock. Although the process has been steadily improved, it has reached the physical constraints imposed by the inertness of nitrogen. Hence, high temperatures, high pressures and H2 feed are required, all consuming copious amounts of energy. Herein, we propose a radically novel approach – plasmonic catalysis. It had been shown to be feasible before, but the activity and selectivity had remained too low.
Climate change is a pressing crisis, which demands immediate action in terms of both: a) greener energy sources and b) lowering energy consumption. Nitrogen activation for the production of ammonia is a process that cannot be avoided because it produces fertilizers, feeding the world, and is projected to play an important role in energy-to-fuel demands (ammonia can be used as a chemical storage for hydrogen).
Plasmonic catalysis is a promising environmentally friendly alternative to classical thermocatalysis, where the interaction between incident light and small nanoparticles (NP) is harnessed to steer and catalyse chemical reactions. The effect is strongly dependent on the NPs. An optimal catalyst material size/shape, composition/formulation, irradiation and reaction conditions must be found. Nowadays, these need not be searched for by trial and error – available computing power has reached levels where atomistic simulations, kinetic modelling and dynamic descriptions of reactors can guide us in setting up the process.
In this project, we will improve nitrogen activation using plasmon-induced nanoparticle photocatalysts. By doing so, we will 1) harness solar energy, 2) use less energy altogether because of a different reaction mechanism and 3) use water and sacrificial reducing agent instead of H2.
We will arrive at this goal with a targeted approach. Instead of trial-and-error testing, we will use first-principle simulations of excited states and incorporate them in a multiscale model. We shall 1) understand the fundamentals of the three plasmonic effects on Ag and Au, 2) computationally probe catalyst materials from the periodic table (starting with plasmonic Ag, Au and catalytic Fe, Ru) and test their alloys/co-catalyst/doping, 3) predict and simulate the effect of nanoparticle shape/size, irradiation/conditions, core-shell and other structures using a multiscale model, 4) synthesize the catalysts and use them to produce ammonia.
A multiscale model, which will include different levels of simulations (quantum, kinetic, reactor-scale) will include a feedback loop to account for changes in NP geometry and structure. Based on theoretical predictions, the most promising catalysts (plasmonics: Ag, Au + catalytic materials) will be synthesized and characterised. Synthesis will include fine controlling of catalyst shape, size and composition. Catalytic testing under various photoconditions will provide an experimental feedback loop to the modelling and synthesis efforts, allowing for an intelligent design of catalyst materials.
We expect 1) fundamental understanding of plasmonic photocatalysis, 2) a multiscale framework for screening of potential plasmonic photocatalysts for different reactions, 3) a superior plasmonic photocatalyst for nitrogen activation.
The project will further a novel catalytic approach, which has not been extensively used yet, although it had shown promising preliminary laboratory results. To avoid pitfalls and dead-ends, the experimental efforts will follow a thorough theoretical understanding and modelling.
