Solar Fuel Generation through Photoelectrochemical Reduction of CO2 Using Copper Porphyrins in Molecularly Designed Reaction Environments

Project Information

SolTIME

Grant agreement ID: 101031365

DOI

10.3030/101031365

Project closed

EC signature date 5 March 2021

Start date 1 September 2021

End date 31 August 2023

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 172 932,48

EU contribution

€ 172 932,48

Coordinated by

FUNDACIO INSTITUT CATALA D'INVESTIGACIO QUIMICA
Spain

Periodic Reporting for period 1 - SolTIME (Solar Fuel Generation through Photoelectrochemical Reduction of CO2 Using Copper Porphyrins in Molecularly Designed Reaction Environments)

Reporting period: 2021-09-01 to 2023-08-31

Summary of the context and overall objectives of the project

Solar technologies have become economically competitive because of investment in solar energy research, spurred in part by concerns over the detrimental environmental consequences associated with conventional energy sources. This has led to an electrical grid with an increasing share of solar electricity; and sometimes, even a surplus. To continue the trajectory towards climate-friendly energy sources, technologies must be developed that can profit from this inexpensive solar energy by storing it for times when the sun is not shining.

One approach to solar fuel production is through the use of photovoltaics to drive electrochemical reactions, using semiconductors as light harvesting components for driving uphill solution-phase reactions to effectively store sunlight in chemical bonds. However, using photo-generated charges to synthesize fuels remains an outstanding challenge, due in part to the large energy requirements needed.

Urgent measures are needed against climate change to limit global temperature rise. Nowadays, we are facing an energy transition where new technologies, together with societal changes, will be needed to shift from a fossil-based system of energy production and consumption to renewable energy sources like wind and solar. The share of renewable energy has considerably increased in the latest years, but these are intermittent energy sources, therefore storage solutions are also needed. Batteries development is an important asset, but additionally transformation of renewable energy to chemical energy in the form of fuels and other commodities is also needed, especially in sectors difficult to electrify.

This research advances the field of solar fuels with an increased understanding of both structure-function relationships in solar-driven electrocatalysis. Managing ammonia oxidation to generate hydrogen fuel using molecular catalysts and sunlight to lower the required energy inputs is a significant advance compared to previous state-of-the-art constructs.

Solar Fuels by Tuning Immobilized Molecular Catalytic Environments (SolTIME) has focused on the development of hybrid cathodes for ammonia oxidation using an integrated approach that houses molecular catalysts in distinct three-dimensional architectures in order to tune the reactivity and selectivity of the embedded catalyst, thus advancing fundamental knowledge of factors favoring performance in solar-driven electrochemical devices.

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

For carbon-free fuel formation, the fuel-forming reaction must be powered by renewable energy. Hydrogen fuel can be obtained through water splitting, but this typically requires multiple photovoltaic cells and/or junctions to drive the reaction. Because of the lower thermodynamic requirements to oxidize ammonia compared to water, solar cells with smaller open circuit voltages can provide the required potential for ammonia splitting.

This project investigated hydrogen production from ammonia by first developing catalysts to lower the energy requirements for ammonia splitting. We found that a ruthenium-based catalyst met the requirements for implementation in a electrocatalytic cell. It was able to be modified for attaching to the electrode and it was sufficiently stable to be analyzed.
We looked at the catalyst in three different environments:
1) directly linked to the electrode,
2) as an amorphous polymer-like coating, and
3) in a well-ordered 2-dimensional framework.

The second approach was the most promising and gave us new insights into how the catalyst works. These hybrid electrodes were used in a cell along with a platinum counter electrode and connected to a perovskite solar cell. When light was shone on the solar panel, the electrochemical cell was able to split ammonia without any additional energy input.

This research was disseminated in a peer-reviewed publication as well as in a manuscript currently under peer review. It was also shared at a non-technical talk for high school students as well as at 2 scientific conferences. It has led to 2 scientific collaborations. Results from this project are being advanced by 2 PhD students that were trained during this project’s realization.

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)

This project advanced the state-of-the-art in using molecular catalysts for ammonia oxidation in three key ways.
First, the construction of a hybrid electrode was the first example of an immobilized molecular catalyst being used in ammonia oxidation.
Second, the use of a oligomer to house the catalyst improved the catalytic performance above anything previously reported.
Third, by integrating the catalyst-functionalized electrode into an electrochemical cell powered by a perovskite solar panel we were able to show the first example of solar-driven ammonia oxidation aided by a molecular catalyst.

As the ammonia economy develops, these findings contribute to the understanding of catalysts for ammonia oxidation. In addition, the project provided training for myself and 2 PhD students on an emerging field in alternative fuel development.

Image of a Ru-based molecular catalyst for ammonia oxidation