TRUSol · Towards Rational Understanding of the Fe-quarterpyridine-mediated CO2 Reduction to Solar Fuels

Towards Rational Understanding of the Fe-quarterpyridine-mediated CO2 Reduction to Solar Fuels

The search for environmentally benign renewable energy sources as alternatives to fossil fuels is essential given increasing energy demands and the consequences of the associated greenhouse gas emissions. Natural catastrophes derived from global warming threaten billions of living beings, with a disproportionate effect on the poorest and most vulnerable people. In addition, we still source about 85% of our energy from combustion of fossil fuels, which not only makes us dependent on a limited resource, but also continues to drive global warming. This may ultimately lead to a point of no return in terms of the balance of our ecosystem as we know it. For all these reasons, there is an urgent need to shift from fossil fuels to sustainable energy sources. On this basis, European initiatives such as the “2030 climate & energy framework” aim to fight climate change by decreasing greenhouse gas emissions by 40% towards a carbon-neutral Europe by 2050 (European Green Deal). A promising direction in renewable energy research applies artificial photosynthesis to generate energy vectors from water, sunlight and harvested atmospheric CO2. The CO2 reduction reaction (CO2RR) is a highly attractive target since it can reduce environmental CO2 levels, while simultaneously providing a wide variety of solar fuels and useful chemicals. To overcome the kinetic and thermodynamic energy barriers of CO2 reduction, the design of efficient, selective and robust catalysts is indispensable for innovative sustainable technologies. Molecular catalysts based on Co phthalocyanines, Fe porphyrins and Ni macrocycles have shown to be highly active and selective towards CO production. They prove the opportunity to study mechanistic pathways through spectroscopic techniques and their catalytic activity can be tuned via specific ligand design. Moreover, the possibility of their immobilization on (photo)electrodes makes molecular catalysts promising candidates for future use in photoelectrochemical (PEC) devices. In this context, understanding the activity, selectivity, mechanism and deactivation pathways of molecular catalysts is fundamental for guiding rational catalytic design. A wide range of experimental techniques, such as X-ray spectroscopy, (spectro)electrochemistry, Mössbauer and electron paramagnetic resonance (EPR) spectroscopies have recently emerged as powerful tools for experimentally revealing the mechanisms of catalytic CO2 reduction. The TRUSol project explores the mechanisms and the factors that control catalytic performance through the rational design of ligands and spectroscopic studies. With this goal in mind, we developed a strategy to synthesize a novel family of Fe-based quaterpyridine-based CO2 reduction catalysts. The new complexes were tested electro- and photocatalytically, combining the molecular catalysts with light absorbing materials. Afterwards, the reaction mechanisms was investigated under steady-state and operando conditions using a spectroscopic toolkit that includes EPR, Mössbauer, X-ray absorption, and emission spectroscopy to shed light on the electronic structures, geometries of key reactive intermediates. Then, taking advantage of the ability of synchrotron techniques to selectively irradiate the metal center, laser/X-ray pump/probe time-resolved X-ray absorption spectroscopy was employed to investigate the highly reactive intermediates on the nanosecond to microsecond time scales.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз