Materials and Mechanisms in Solar Hydrogen Production CO 2 + H 2 O Jan Philipp Hofmann Emiel Hensen
Photoelectrochemistry Crucial parameters: Bandgap Lifetime of charge carriers Concentration of the defects Charge carriers free path Stability against photocorrosion Interface properties Requirements: solar to H 2 efficiency > 10 % lifetime > 10 years
Materials choice: band gaps and band positions E 0 vs NHE / V -2-1 0 1 2 3 4 H + /H 2 H 2 O/O 2 GaP 2.25 ev GaAs 1.4 ev TiO 2 3.2 ev 388 nm ZnO 3.2 ev Fe 2 O 3 2.1 ev 590 nm 517 nm Cu 2 O 2.1 ev WO 3 2.6 ev SnO 2 3.8 ev ZnS 3.7 ev 335 nm FeS 2 0.9 ev CdSe 1.7 ev CdS 2.4 ev / Inorganic Materials Chemistry 28-4-2014 PAGE 2
Anton Litke, PhD Bjorn Joos, MSc Materials for light harvesting making use of faults: twinned Cd 0.5 Zn 0.5 S no additives 0.1M NaOH 0.1M EN 0.1M KCl 20 30 40 50 60 2 / degree H 2 production / mmol g -1 h -1 H 2 production / mmol g -1 h -1 20 10 0 2 1 0 optimized loading: 5.7 mg in 50 ml 23.7 19.2 16.8 no co-cat. 1wt% Pt 1wt% NiS 2.3 loading 50 mg in 50 ml 1.06 0.87 0.43 no add. 0.1M NaOH 0.1M EN 0.1M KCl twinning in pyrite FeS 2 zinc blende structure 28-4-2014 PAGE 3
Twinned Cd 0.5 Zn 0.5 S: Enhanced charge carrier separation CB E, ev H 2 H + /H 2 H + S 2 2- S 2 2- /S 2- S 2- VB M. Liu et al., Nature Communications, 2013, 4, 2278. HR-TEM + TEM hologram of Cd 0.5 Zn 0.5 S courtesy of T. Niermann, TU Berlin / Inorganic Materials Chemistry 28-4-2014 PAGE 4
Probing reactions on photocatalysts Combined IR and UV-Vis Spectroscopy Anton Litke, PhD IR probe reactions at surface of nanoparticles UV-Vis probe photoluminescence UV-Vis probe absorption target time resolution 10 8-10 9 s / Inorganic Materials Chemistry 28-4-2014 PAGE 5
Interfaces: Theory of water oxidation e.g. Au/TiO 2 & CoO/TiO 2 Bartek Szyja, PD Mechanism: 2 H 2 O 4 H + + 4 e + O 2 Au 4 /TiO 2 Co 4 O x /TiO 2 / Inorganic Materials Chemistry 28-4-2014 PAGE 6
Cu 2 O as photoabsorber Quanbao Ma, PD Andrey Goryachev, PhD Elif Teksen, BSc Earth-abundant materials production by chemical bath deposition or hydrothermal reaction ph dependent preferential growth in chemical bath 28-4-2014 PAGE 7
Cu 2 O as photoabsorber stability Cu 2 O before photoelectrochemical reaction Cu 2 O after photoelectrochemical reaction / Inorganic Materials Chemistry 28-4-2014 PAGE 8
Protection Multilayer model systems co-catalyst Paracchino et al., Nat. Mater., 10, 2011, 456. R,C (PL) R, C (Abs) layer model of photoelectrode with resistances and capacitances of layers (left) and interfaces (right) Protective layer (PL) Cu 2 O (Absorber) FTO glass R (PL CoCat) R (Abs PL) / Inorganic Materials Chemistry 28-4-2014 PAGE 9
Quanbao Ma, PD Andrey Goryachev, PhD Charge carrier dynamics probed by photoelectron spectroscopy bias voltage dependent shift of XPS peaks [1] Inorganic Materials Group/Solar Fuels Catalysis [1] U.K. Demirok, et al., J. Phys. Chem. B, 108 (2004) 5179-5181 PAGE 10
Interfaces: Dynamic XPS Dynamic XPS = analogue of electric impedance spectroscopy + no electrolyte surface science (vacuum) technique + not destructive no photocorrosion + surface sensitive non bulk analysis + chemically specific element specific analysis of electronic behavior R C Data: (Ertas, Demirok, Atalar, & Suzer, 2005; Suzer, Sezen, Ertas, & Dâna, 2010) / Inorganic Materials Chemistry 28-4-2014 PAGE 11
Suggestion for Goals, challenges and roadmap Stable Solar Fuels device with >15% overall efficiency 1. Novel light harvesting materials with high quantum h 2. Efficient co-catalysts 3. Earth-abundant materials 4. Device integration (high-tech system) 5. Integration into current energy infrastructure Highly multidisciplinary efforts needed Chemistry, Physics, Engineering / Inorganic Materials Chemistry 28-4-2014 PAGE 12
The Solar Fuels Scientist recently seen in Eindhoven / Inorganic Materials Chemistry found at: bsrobo.wikispaces.com 28-4-2014 PAGE 13
Nederlands Instituut voor Onderzoek in de Katalyse Solar Fuels Catalysis Graduate programme started in September 2013 Highly interdisciplinary Master and PhD programmes Focus on all aspects of Solar Energy Conversion into Clean Fuels Utrecht University (UU) In-situ Spectroscopy of Catalyst Materials Technical University Eindhoven (TU/e) Catalyst Materials and Mechanisms Leiden University (UL) Electrochemistry / Electrocatalysis Twente University (UT) - Photocatalysis
Solar Fuels Catalysis Graduate Programme Prepare the students for a career in science by offering them the best possible training and education in the challenging research field of catalytic conversion of sun light, carbon dioxide and water into fuels 15
Thanks for your attention! / Inorganic Materials Chemistry found at: bsrobo.wikispaces.com 28-4-2014 PAGE 16
/ Inorganic Materials Chemistry 28-4-2014 PAGE 17