Photoinduced water splitting is the ultimate source of storable and clean energy in the form of H2. For over four decades, to optimize this process has been the grail of sustainable energy research.
The possibility of splitting water through photoinduced radical reactions enabled by a simple organic chromophore is a recent theoretical prediction, which already counts on preliminary experimental corroboration. These reactions, however, are not the ones commonly expected in water splitting processes, as they involve hydrogen radicals rather than protons. For this reason, they may represent a deep paradigm shift in the H2 photocatalysis from water, if a series of bottlenecks in terms of recombination rates can be eliminated.
At this point, not much is known about these radical reactions. The WSplit project has been set up exactly to apply state-of-the-art experimental and computational techniques to close this knowledge gap. The project joins the expertise of three research terms, two experimental and one computational, to disentangle the reactive process through a combination of a large battery of techniques, including theoretical simulations, time-resolved experiments, and laser spectroscopy coupled to mass spectrometry. This analysis will be applied to isolated microsolvated clusters. The goals of the project are:
• To develop and use advanced experimental and computational methods to characterize the radical dynamics in microsolvated pyridine-water clusters.
• To use this basic knowledge to search for ways to reduce the recombination rate in these photoreactions.
• To test the efficiency of this class of radical reactions when photoinduced by other organic chromophores.
The choice of systems to be investigated is based on the preliminary experimental and theoretical information available on these radical reactions. It is also set to allow clean spectral signatures from the experiments done in small cold cluster obtained in supersonic jet, allowing an optimal synergy with the theoretical simulations.
The theoretical work will be split in two axes: method developments and simulations. The method development axis will focus on the implementation of a mixed quantum-classical dynamics approach to simulate tunneling using rare-events sampling and machine learning algorithm. This methodology will be then used to investigate the excited-state nonadiabatic dynamics of (Py)k(H2O)n clusters (k = 1,2; n = 1-3).
The experimental work will also be split in two axes: time-resolved spectroscopy and photochemical measurements. The first axis will focus on measuring the picosecond dynamics of the photoinduced dissociation of water. The second axis will use laser spectroscopy coupled to mass spectrometry to find the role of the OH radical in the reaction dynamics, to determine what is controlling the NH dissociation of the pyridinyl radical, and to check whether other organic chromophores may be more productive than pyridine.
WSplit is a three years’ project focused on fundamental research. It is the first step of a larger research programme, whose goal is to build a water-splitting photocatalytic cell using an organic chromophore as a co-catalyst. The maturation of the project will allow us to orient the investigations towards more applied topics in the near future; to access European funds through “Future and Emerging Technologies” calls, as the processes proposed here perfectly fits in the “Key Enabling Technologies” concentration area of the Horizon 2020.
Monsieur Mario BARBATTI (Institut de Chimie Radicalaire)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
ISMO Institut des Sciences Moléculaires d'Orsay
PIIM Physique des interactions ioniques et moléculaires
ICR Institut de Chimie Radicalaire
Help of the ANR 306,417 euros
Beginning and duration of the scientific project: September 2017 - 36 Months