Earth-Abundant Molecular Z-Scheme Photoelectrochemical Cell for Overall Water-Splitting

Christopher D. Windle (1) , Hiromu Kumagai (2) , Masanobu Higashi (3) , Romain Brisse (4) , Sébastien Bold (1, 5, 6) , Bruno Jousselme (4) , Murielle Chavarot-Kerlidou (1) , Kazuhiko Maeda (2) , Ryu Abe (3) , Osamu Ishitani (2) , Vincent Artero (1)

1 SolHyCat - Solar fuels, hydrogen and catalysis
2 Department of Chemistry, School of Science
3 Department of Energy and Hydrocarbon Chemistry
4 LICSEN - Laboratoire Innovation en Chimie des Surfaces et NanoSciences
5 Abber Center of Photonics
6 Leibniz Institute of Photonic Technology Jena, Department Functional Interfaces

A push-pull organic dye and a cobaloxime catalyst were successfully co-grafted on NiO and CuGaO$_2$ to form efficient molecular photocathodes for H$_2$ production with >80% Faradaic efficiency. CuGaO$_2$ is emerging as a more effective p-type semiconductor in photoelectrochemical cells and yields a photocathode with four-fold higher photocurrent densities and 400 mV more positive onset photocurrent potential compared to the one based on NiO. Such an optimized CuGaO$_2$ photocathode was combined with a TaONǀCoO$_x$ photoanode in a photoelectrochemical cell. Operated in this Z-scheme configuration, the two photoelectrodes produced H$_2$ and O$_2$ from water with 87% and 88% Faradaic efficiency, respectively, at pH 7 under visible light and in the absence of an applied bias, equating to a solar to hydrogen conversion efficiency of 5.4×10$^{−3}$%. This is, to the best of our knowledge, the highest efficiency reported so far for a molecular-based noble metal-free water splitting Z-scheme.

Domains: Chemical Sciences; Material chemistry; Chemical Sciences; Catalysis

Christopher D. Windle, Hiromu Kumagai, Masanobu Higashi, Romain Brisse, Sébastien Bold, et al.. Earth-Abundant Molecular Z-Scheme Photoelectrochemical Cell for Overall Water-Splitting. Journal of the American Chemical Society, 2019, 141 (24), pp.9593-9602. ⟨10.1021/jacs.9b02521⟩. ⟨cea-02147070⟩