Biomimetic Copper Complexes for Energy Conversion Reactions

Project Information

Cu4Energy

Grant agreement ID: 637556

DOI

10.3030/637556

Project closed

EC signature date 10 March 2015

Start date 1 May 2015

End date 30 April 2020

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 500 000,00

EU contribution

€ 1 500 000,00

Coordinated by

UNIVERSITEIT LEIDEN
Netherlands

Periodic Reporting for period 4 - Cu4Energy (Biomimetic Copper Complexes for Energy Conversion Reactions)

Reporting period: 2019-11-01 to 2020-04-30

Summary of the context and overall objectives of the project

Water oxidation (WO) and oxygen reduction (OR) are crucial reactions to produce and to consume solar fuels. It is important that WO and OR occur with very high catalytic rates with only a very small thermodynamic driving force. In these terms, Natural catalysts perform significantly better than the artificial systems that are currently employed in fuel cells and electrolyzers. Especially the copper enzyme Laccase operates fast at a low overpotential. In principle one could use the same design principles used in the enzymatic systems to produce artificial catalysts for OR and WO. The aim of the proposal is to significantly increase of fundamental understanding of the design principles for molecular OR and WO catalysts and to deliver new and very active molecular copper catalysts for OR and WO at the end of the project.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Due to a very fast equilibrium between coordination and de-coordination of ligands their corresponding copper complexes are very labile. Formation of small amounts of non-coordinated copper easily leads to formation of copper or copper oxide deposits on the electrode.
Many of the molecular catalysts that were explored during the initial stages of the project resulted therefore in formation of deposits on the electrode, even despite some of these were claimed to be molecular catalysts in literature reports previously.
We have unraveled the mechanism of oxygen reduction at various stable, mononuclear and homogeneous copper sites. In these reactions hydrogen peroxide is an obligatory intermediate. On one hand this opens up the possibility to produce hydrogen peroxide electrochemically in a sustainable process. On the other hand this limits potential efforts to push the onset of oxygen reduction above that of the equilibrium potential of hydrogen peroxide oxidation. Minimal yields of peroxide were obtained in case of trinuclear copper sites.
Copper based water oxidation catalysts more easily allow for adjustment of its onset potential. Similar to ruthenium complexes electron donating and/or electron withdrawing ligands at the ligand periphery have a massive effect on the electronics of the catalyst.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

An extremely fast catalyst for the oxygen reduction reaction was developed. Reduction of dioxygen to hydrogen peroxide proceeds with almost two million turnovers per second. We are currently exploring this reaction for the sustainable electrochemical synthesis of hydrogen peroxide.
From the oxygen evolution part of the overall project we have been able to draw clear relationships between the catalyst structure, electronic effects at the catalytic site, and the reaction conditions. This allows us to pinpoint clear design principles for further catalysts development.

erc-summary.jpg