”In this bright future you cannot forget your past” B. Marley
The driving philosophy of our work has been developed when Jonathan started his first postdoc in the group of Prof Matthias Arenz at the University of Copenhagen, Denmark, and further collaboration when Prof Matthias Arenz moved to the University of Bern, Switzerland. The surfactant-free polyol synthesis was then used and developed together with the group of Dr Sebastian Kunz at the University of Bremen, Germany. This synthesis first reported in 2000 by Wang et al. allows producing, without surfactants, small size precious metal nanoparticles based on a the polyol synthesis developed by Fievet and co-workers.
However, this approach requires relatively viscous solvents and washing steps. A significant achievement in 2018 was to develop and patent a synthesis using mono-alcohols like methanol and ethanol. This approach leads to catalysts with high activity produced in a very simple way. This also leads to ideal model systems to understand nanomaterial formation. This new synthetic approach further leads to a range of opportunities with a second patent application in 2021 towards the development of room temperature syntheses of surfactant-free precious metal nanomaterials.
Typical colloidal syntheses of nanomaterials often require many chemicals and high temperatures and/or controlled gas atmosphere. Our approach alleviate from these challenges. Ultimately we envision our syntheses to be ideal simpler model systems to unravel the actual role of different molecules and additives used as solvent, reducing agents, and/or stabilizers, in order to provide a more complete chemical and structural picture of nanomaterial formation mechanism(s).
Our interest in this direction is going towards bi- and multi- metallic nanomaterials: to reduce the amount of precious metals and tune the shape, structure and properties of nanomaterials.
Characterisaiton is a must to understand how nanoparticles form and/or evolve during their use, for instance as cataysts. This brings useful knowledge to tune the properties of the nanomaterials and/or propose mitigation strategies to optimise their synthesis but also their lifetime in real-life conditions.
We use a range of characterisation such as UV-vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and more advanced techniques like small angle X-ray scattering (SAXS), X-ray total scattering with pair distribution function analysis (PDF), X-ray absorption spectroscopy (XAS), etc., in house or via collaborations, e.g. at synchrotron facilities. The fun starts when different techniques can be combined to learn more about the nanoscale.
Our interest in this direction is to understand better how surfactant-free nanomaterials are formed and stabilized, moving towards a deeper understanding of the nanomaterial formation at the chemical and structural levels. See here and here.
Precious metal nanomaterials are relevant for almost any type of catalysis. Precious metal nanoparticles are typically supported on another material and in recent years colloidal precious metal nanoparticles have shown to be ideal system to perform fundamental catalytic studies. We believe that our surfactant-free colloidal approach will help to bridge the gap academia-industry. Surfactant-free nanoparticles are more simply functionalized to develop hybrid homogeneous-heterogeneous catalysts. Surfactant-free nanoparticles are often more active than the state-of-the-art. While proof of concepts have been made in particular for electro-catalytic applications, it is now time to explore further these features for more systems. See examples here.
Our interest in this direction is to keep exploring the benefits of colloidal surfactant-free nanoparticles.
In a first range of applications are energy conversion reactions and electrocatalysis at broad, such as reactions with small molecules (e.g. oxygen evolution reaction ORR, oxygen evolution reaction OER, and possibly ultimately CO2 reduction reaction CO2RR or nitrogen reduction reaction NRR) or small organic molecules oxidations (e.g. methanol oxidation reaction MOR, ethanol oxidation reaction EOR or formic acid oxidation FAO). Since there is a lot to explore, we are very open to receiving input from interested collaborators and prospective team members.
In a second range of applications are all sort of liquid and gas phase heterogeneous catalytic processes where our colloidal surfactant-free precious metal nanoparticles supported on various support materials, with tuned nanoparticle size, composition, loading and so interparticle distances, can be relevant. See examples here. Since there is a lot to explore we are very open to receiving input from interested collaborators and prospective team members.
Since precious metals are critical raw materials their re/up-cycling is key. This can be achieved by developing stable materials that do not degrade over time, materials than can be re-used several times, and/or developing ways to recover the precious metals. For instance, converting nanomaterials back to molecular complexes that can then be used to re-synthesize nanomaterials would be an important achievement.
Although we have little expertise in this area yet, we are very much looking forward to look into it in the future.