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Nicolas Kaeffer

Construction of molecular cathodes and photocathodes for hydrogen evolution

Published on 11 March 2016

Thesis presented on March 11, 2016

Solar fuels generated from the light-induced splitting of water into H2 and O2 is an appealing strategy for securing future energy. The use of platinum for catalyzing hydrogen evolution may be bypassed with earth-abundant catalysts. In a previous study, our lab realized the immobilization of a proton reduction catalyst, the cobalt diimine-dioxime molecular complex, within a cathode material steadily evolving H2 from fully aqueous media. In this work, we report on the implementation of this catalyst into light-driven devices. Operating conditions in the solvent of interest, water, were screened. The molecular catalyst degrades when free in solution, but retains activity when supported on an electrode, even in the presence of O2, and could thus be integrated into a tandem cell. Further on, new derivatives of the catalyst were developed for the attachment onto transparent conducting oxides. Co-grafted photocathodes were constructed by anchoring a functionalized catalyst along with photosensitizers onto p-type NiO. These architectures were checked by a whole set of analytical techniques and light-driven catalytic hydrogen evolution was achieved by photocathodes assessed under device-related photoelectrochemical conditions. Immobilizable dye-catalyst dyads were also successfully synthetized as alternative derivatives and open up new possibilities to develop molecular photocathodes.

Hydrogen, Catalysis, Photoelectrocatalysis, Surface chemistry, Electrochemistry

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