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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - ELCOREL (Electrochemical Conversion of Renewable Electricity into Fuels and Chemicals)

Teaser

Summary

The efficient and environmentally sustainable generation of energy is the most pressing challenge for European science and technology in the 21st century. The increasing environmental awareness of European societies, together with depletion of easily accessible fossil fuels and geostrategic considerations, calls for a paradigm shift away from large-scale technologies that deploy limited reserves and generate huge amounts of waste. Renewable energy sources, such as biomass and solar or wind energy, are the only viable long-term alternative for an infrastructure based on the concepts of recycling and the distributed generation, storage and use of energy.

The large-scale implementation of renewable energy sources necessitates the introduction of technology that can deal with the intermittent nature of renewable energy sources and their restricted predictability. These technical problems can be successfully mitigated through electrochemical technologies. While electricity is traditionally stored in electrochemical devices such as supercapacitors and batteries, large-scale implementation of renewable electricity will require to extend the existing energy storage technologies by the (photo-)electrochemical conversion to fuels and other chemicals, such as hydrogen obtained from water splitting, or small organic molecules obtained through electrochemical carbon dioxide reduction.

The scientific objectives of ELCOREL are: (1) to deploy a systematic theoretical description of electrocatalysis by means of quantum chemical calculations to gain fundamental insight into the rational design of electrocatalysts for water oxidation and CO2 reduction; (2) to implement advanced techniques of material synthesis to prepare novel nano-particulate catalysts for multiple electron redox reactions meeting the predictions of the rational computational design; (3) to investigate the dynamics of nanostructured metal and metal-oxide interfaces in the electrocatalytic processes using state-of-the-art electrochemical and spectroscopic techniques and (4) to engineer the knowledge and materials developed under (1)-(3) into working electrochemical applications which meet the cost and scale requirements of the industrial partners, and (5) to transfer the knowledge to the public so that the society can discuss the best options for the implementation of the Paris agreement to reshape the society based on carbon energy into the one based on renewable energy sources.

Work performed

The activity concentrated on systematic investigations of the nature of electrocatalytic oxygen evolution and carbon dioxide reduction, development of novel catalysts and their implementation into test electrolyzers.

In respect to electrocatalytic oxygen evolution the consortium extended the DFT based computational techniques to develop fundamentally error model of the oxygen evolution thermodynamics on semiconducting oxides. This model outlines and removes the intrinsic drawback of the conventional model(s) which are unable to replicate correctly the binding energy of the oxo intermediates on semiconducting surfaces. This model improvement is fundamental for rational design of OER catalysts targeted for alkaline media. On the experimental side the consortium developed low temperature synthesis of nanoparticulate catalysts both for acid as well as alkaline media. In the acid media the consortium developed novel class of pyrochlore based catalyst based on catalytic behavior of Ru and Ir with reduced transition metal content, increased activity and improved stability with respect to the benchmark IrO2 based catalysts. The control of the activity can be achieved by a local structure control when the overall activity is related to the spacing of the transition metal cations. The consortium also developed protocol for gas phase deposition of extended oriented oxide surfaces for fundamental mechanistic studies. The consortium also developed procedures for deposition and integration of the developed catalyst into alkaline electrolyzers.

In respect to catalytic carbon dioxide reaction the consortium followed the two directions leading to controlled 2 electron reduction (to CO or formic acid) as well as multiple electron reduction to alcohols and hydrocarbons. In the case of the 2 electron reduction we have employed quantum chemical methods to describe the role of single atom catalysts both on carbon as well as on copper based surfaces. From the experimental point of view the consortium performed systematic investigations affecting the CO2 reduction process - namely the role of the local pH (and connected dis-proportionation reactions) and the process selectivity control resulting from the supporting electrolyte adsorption or from polymer modification of the electrode surface. In the case of the multiple electron reduction of carbon dioxide the main attention was paid to the CO2 reduction on catalysts based on carbon multi-wall nanotubes and oriented nanocrystalline oxides. In the case of carbon multi-wall nanotubes the selectivity of the process is achieved by a variation of temperature when the formation of gaseous products (mainly of the methane) is promoted at increased processes temperatures. Thee industrial consortium members also developed procedures for nanocrystalline alloy catalyst into gas diffusion electrodes and their integration into electrolyzer.

Final results

The main progress beyond the state of the art is found in the following areas:

in the activities relevant to the oxygen evolving catalysts it is conceptually novel improvement of the theoretical models to avoid finite size and band structure related systematic errors. The novel theoretical approaches will be utilized in prediction of the behavior of mainly Ni based perovskite OER catalyst. This extension of the theoretical modeling will be mirrored in experimental synthesis of the novel nanoparticulate catalysts based on Ni based perovskites utilizing the local structure and transition metal synergy control of the oxygen evolution activity. this second generation of the catalysts will be implemented and tested in the laboratory scale electrolyzers.

in the activities relevant to carbon dioxide reduction the main progress beyond the state of the art was achieved in theoretical description of the the single atom catalysts. From the experimental point of view the main progress is seen in elucidation of the supporting electrolyte role in steering the selectivity of the CO2 reduction towards Co or formic acid. The formate producing catalysts were also successfully integrated into gas diffusion electrodes which can be optimized in the following period to meet the feasibility standards of the industrial scale formate production. With respect to the multi electron carbon dioxide reduction the main achievement is seen in the implementation of carbon nanotubes as alkane producing catalyst. Further development in this respect can be seen in gaining the fundamental understanding of the reduction mechanism on nonmetal catalyst where the initial experiments clearly outline different binding mechanisms between metals and non-metals.