Fe/S: Toward Energy with Nanoparticles – FeSTEN

The bio-inspired approach implies that we do not aim to precisely mimic the nature, but rather that we build a simple functional model that has some of the characteristics of the natural system without the complex cell machinery. To do so, several severe challenges have to be assessed and considered:
• preparation of nanometric size Fe/S particles (i.e. = 10 nm),
• control of the Fe/S ratio of the material,
• solubility and stability of the nanoparticles in aqueous media,
• reversibility of the catalytic reaction (H+ reduction and H2 oxidation).
The novelty and originality of this approach combines the abundance and cheapness of the raw materials (iron is 2nd most abundant metal and sulfur the 14th most abundant element in the Earth’s crust) to the research of a simple preparation for a Fe/S nanometric material, together with a comprehensive catalytic study of the performance of the designed catalyst.
Another point that will be considered is the reversibility of this reaction. Very few molecular systems are indeed presenting catalytic activity toward dihydrogen oxidation to release protons and electrons. This reaction is crucial in terms of fuel cell activity, since electrons have to be ‘recaptured’ after having been stored in chemical bonds. The systems that will be prepared will be designed to perform both sides of the reaction.
Furthermore it is well known that iron sulfides are an intrinsic and essential part of the biogeochemical sulfur cycle, and have been associated with the ‘iron-sulfur world’ hypothesis for the development of life. This concept proposes that iron sulfides played an extensive role in prebiotic organic synthesis on the early Earth. This project seeks to propose a path to link the chemistry of iron sulfides, notably in term of catalysis, and the microbial respiration based on Fe/S enzyme catalysis.

The results obtained so far showed that Fe3S4 nanoparticles synthesized by the polyol process are very active towards the reduction of protons into dyhydrogen. Bulk electrolysis run in neutral water have been performed, and hydrogen evolution for time lengths up to 5 days with no loss in activity. Overpotential is a bit higher than for other transition metal catalysts, but the stability and the ease of preparation is clearly favored in our system. This catalytic system has been patented in june 2013.

We are currently running more stability tests, as well as some experiments with other stoechiometries for the iron/sulfide ratio. Other types of catalysis are also envisaged, such as CO2 reduction or O2 reduction.

European patent EP13305888.3: “Iron sulfide based catalyst for electrolytic water reduction into hydrogen gas“.

Global energy consumption is projected to increase in the future years because of population and economic growth. This evolution requires the invention and development of new carbon-neutral energy sources at a high scale in order to supply this demand while maintaining the atmospheric CO2 content at a low level. To fulfill this need, solar energy seems by far the largest exploitable sustainable resource, but due to the period of sunshine intermittency, it has to be stored and dispatch. One of the attractive approaches consists in storing solar energy in terms of chemical energy through the formation of chemical bonds, which is achieved by the photosynthetic process. In this context, this proposal focuses on one of the ‘hydrogen economy’ paradigm, namely the preparation of cheap, sustainable and robust catalyst for dihydrogen evolution/uptake. We propose here to prepare and characterize Fe/S nanoparticles as bio-inspired catalysts and study the catalytic activity of such materials by the mean of electrochemistry. The two partners involved in this project are combining their expertise from their respective fields, nanomaterial preparation and characterization on one hand, and electrochemistry on the other hand, to design and improve catalysts from simple and cheap starting materials.