IRS-PEC · Elucidating the water photo-oxidation mechanism by infrared spectroscopy
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2017-02-01 → 2019-01-31
- EU contribution
- €165,599
- Participants
- 1
- Scheme
- MSCA-IF-EF-ST
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Results in brief
Elucidating the water photo-oxidation mechanism by infrared spectroscopy
For a society to solely depend on renewable energy sources, the fluctuating energy demand as well as the intermittent nature of renewable energies need to be addressed. A promising solution is to use the energy to produce chemicals (so-called solar fuels), either for use in the chemical industry or to act as a storage medium. A likely candidate that can serve both is hydrogen (H2). Photoelectrochemical (PEC) water splitting is a potentially effective method for direct conversion of solar power into chemical energy in the form of hydrogen and oxygen (O2). Currently, the water oxidation reaction is limiting the water splitting efficiency. Therefore, the main objective is to gain insight into the water oxidation reaction. If we know at which surface sites the oxidation reaction takes place and which are the intermediate species formed during the water splitting process, we can fabricate tailored photoelectrodes with, for example, a maximum number of catalytic sites. Thereby, the photo-oxidation process can be enhanced and, hence, the water splitting efficiency improved. To this end, a PEC set-up and samples are designed, developed, and fabricated with which reaction intermediates can be detected by means of infrared (IR) spectroscopy during actual operating conditions, the so-called infrared spectroscopy photoelectrochemical (IRS-PEC) cell. This enables us to elucidate the chemical reactions occurring at the surface of a photo-electrode during operation. The unique combination of PEC analysis with IR spectroscopy will gain fundamental insight into the water oxidation mechanism during actual operating conditions. If we know at which surface sites the oxidation reaction takes place, we can fabricate a photoelectrode with a maximum number of those catalytic sites. Thereby, enhancing the photo-oxidation reaction and, hence, improving the water splitting efficiency. It has the potential of making water splitting an efficient, clean, and viable method to store renewable energy in the form of hydrogen and to produce hydrogen for the chemical industry. The main objective is to gain insight into the water photo-oxidation reaction. To this end the work was divided in three specific objectives: 1. Design and fabrication of an IRS-PEC cell for operando measurements 2. Demonstration of the proof-of-principle of the IRS-PEC cell 3. Study oxidation mechanism of a novel material Conclusion of the action: 1. Samples for IRS-PEC measurements can be fabricated and are stable (no delamination) 2. Large area and low temperature (<300 °C) fabrication routes of Fe2O3 photoanodes can be fabricated with good PEC performance 3. Surface intermediates can be detected 4. Novel photocatalyst (Ag3PO4) can be studied by IR spectroscopy
Data: CORDIS, © European Union
Project objective
Hydrogen is a highly versatile fuel that is believed to become one of the key pillars to support our future energy infrastructure. A clean and renewable method to produce hydrogen is to use sunlight to convert water into hydrogen in a photoelectrochemical (PEC) cell. The exact mechanism of this photocatalytic water splitting remains a largely unexplored area. In this project, I will provide insight into the more challenging oxidative half-reaction occurring at metal-oxide surfaces.To gain insight into the oxidative half-reaction, surface groups residing at the solid/liquid interface will be measured by infrared spectroscopy during actual device operation. Hereto, a PEC cell will be constructed with a multiple internal reflection element as key component; it will ensure a high sensitivity while simultanously act as substrate for the working electrode. The novel approach to apply a bias voltage allows for photoelectrochemical analysis, but also allows ‘freezing’ of the surface species thereby relaxing the constraints of a fast measurement speed.From in operando measurements the density and nature of surface groups present at a well-defined metal-oxide surface will be obtained as a function of electrolyte pH. With this knowledge conclusions can be drawn on which surface sites initiate the oxidation reaction, which groups present sites where (intermediate) reactions with high activation energies take place, and where undesired hole-trapping and electron-hole recombination are most likely to occur. Thereby providing fundamental insight into the water oxidation mechanism, which is required to engineer a photoelectrode material with high photocurrents and low onset potentials. Additionally, the quantified information on surface species densities is much-needed input in models and simulations. Furthermore, a tool will be delivered with which the critical steps in the oxidation reaction can be disclosed as a function of pH.
Original text from CORDIS.
Participants
- STICHTING NEDERLANDSE WETENSCHAPPELIJK ONDERZOEK INSTITUTEN · UtrechtCoordinatorNetherlands
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Data: CORDIS, © European Union