Photoelectrodeposition of Amorphous Cobalt and Manganese Oxide Hydroxides onto Fe2WO6 Photoelectrodes

Moritz Kölbach^a, Sebastian Fiechter^a, Peter Bogdanoff^a

^aElectrochemistry, Electrocatalysts, Water oxidation, Manganese oxide, Cobalt oxide, Electrodeposition, Solar fuels

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting 2018 (NFM18)

S2 Light Driven Water Splitting

Torremolinos, Spain, 2018 October 22nd - 26th

Organizers: Wolfram Jaegermann and Bernhard Kaiser

Poster, Moritz Kölbach, 276
Publication date: 6th July 2018

In the development of photoanodes for light-induced water oxidation it is often essential to deposit a co-catalyst that either passivates surface states at the electrode/electrolyte interface or catalyzes the oxygen evolution reaction (OER). In this contribution we demonstrate the influence of cobalt as well as manganese oxide/hydroxide on semiconducting and photosensitive iron tungstenate Fe₂WO₆ layers. Thin films of amorphous CoO_xOH_y and MnO_xOH_ywere deposited on this ternary oxide [1-3], a novel semiconductor with an indirect/direct band gap of 1.7 eV and 2.4 eV. After deposition of a CoO_xOH_y film on top of the electrode the photocurrent density could be doubled while in case of amorphous MnO_xOH_y the onset potential under illumination could be shifted by ~250mV. Annealing the electrodes after photoelectrodeposition of MnO_xOH_y at 500°C, crystalline a‑Mn₂O₃ is formed. However, after this treatment the photosensitivity of the electrode is completely lost. This behavior can be explained by a reaction of Mn₂O₃ with Fe₂WO₆ under formation of a (Fe_1-xMn_x)₂WO₆ interface layer acting as a trap for excited charge carrieres. Our results show that the deposition of amorphous co-catalysts on iron tungstenate films can strongly influence its photoelectrochemical performance.

References:

[1] Kölbach, M.; Fiechter, S.; van de Krol, R.; Bogdanoff, P. Evaluation of electrodeposited α-Mn2O3 as a catalyst for the Oxygen Evolution Reaction; Evaluation of Electrodeposited α-Mn2O3 as a Catalyst for the Oxygen Evolution Reaction. Catalysis Today 2017, 290, 2–9.

[2] RAMÍREZ, A.; HILLEBRAND, P.; STELLMACH, D.; MAY, M. M.; BOGDANOFF, P.; FIECHTER, S. Evaluation of MnOx, Mn2O3, and Mn3O4 Electrodeposited Films for the Oxygen Evolution Reaction (OER) of Water. J. Phys Chem. C 2014, 118, 14073-14081.

[3] HILLEBRAND, P.; RAMÍREZ-CARO, A.; CALVET, W.; BOGDANOFF, P.; FIECHTER, S.: On the Structure-Function Relationship of Cobalt and Manganese Oxides as Oxygen Evolving Catalysts for Light-Driven Water Electrolysis: An In-Line Synchrotron Radiation Photoelectron Spectroscopy Study; ECS Transactions, 61 (2014) 9-20. HILLEBRAND, P.; RAMÍREZ-CARO, A.; CALVET, W.; BOGDANOFF, P.; FIECHTER, S.: On the Structure-Function Relationship of Cobalt and Manganese Oxides as Oxygen Evolving Catalysts for Light-Driven Water Electrolysis: An In-Line Synchrotron Radiation Photoelectron Spectroscopy Study; ECS Transactions, 61 (2014) 9-20. HILLEBRAND, P.; RAMÍREZ-CARO, A.; CALVET, W.; BOGDANOFF, P.; FIECHTER, S.: On the Structure-Function Relationship of Cobalt and Manganese Oxides as Oxygen Evolving Catalysts for Light-Driven Water Electrolysis: An In-Line Synchrotron Radiation Photoelectron Spectroscopy Study; ECS Transactions, 61 (2014) 9-20. Hillebrand, P.; Ramírez-Caro, A.; Calvet, W.; Bogdanoff, P.; Fiechter, S. Hillebrand, P.; Ramírez-Caro, A.; Calvet, W.; Bogdanoff, P.; Fiechter, S. On the Structure-Function Relationship of Cobalt and Manganese Oxides as Oxygen Evolving Catalysts for Light-Driven Water Electrolysis: An In-Line Synchrotron Radiation Photoelectron Spectroscopy Study. ECS Transactions 2014, 61, 9-20.

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