The development of robust and inexpensive semiconducting materials that operate at high efficiency are needed to make the direct solar-to-fuel energy conversion by photoelectrochemical cells economically viable. In this presentation our laboratory’s progress in the development new light absorbing materials as photocathodes will be discussed along with the application toward overall solar water splitting tandem cells for H₂ production. Specifically, this talk will highlight recent results with the ternary oxide CuFeO₂, 2D transition metal dichalcogenides, and organic (π-conjugated) semiconductors as solution-processed photoelectrodes.

With respect to CuFeO₂, in our recent work [1] we demonstrate state-of-the-art sacrificial p-type photocurrent with optimized nanostructuring. Recent results addressing interfacial recombination by the electrochemical characterization of the surface states and attached co-catalysts will be presented along with approaches to overcome the limitations of this material.

In addition, two-dimensional (2-D) transition metal dichalcogenides (TMDs) generally have intriguing electronic properties making them promising candidates for high-efficiency solar energy conversion. However, it is notoriously difficult to fabricate thin films of 2-D TMDs over the large areas required to convert solar energy on a practical scale. We recently developed a simple method to fabricate high-quality thin films of 2-D layered TMDs at low cost and with good efficiency towards solar-to-fuel energy conversion [2]. The challenges with charge transport, separation [3] and water redox catalysis in these systems will also be discussed with respect to the 2D flake size.

Finally, with respect to π-conjugated organic semiconductors, in our recent work [4] we demonstrate a π-conjugated organic semiconductor for the sustained direct solar water oxidation reaction. Aspects of catalysis and charge-carrier separation/transport are discussed.

[1] Prevot, M. S.; Li, Y.; Guijarro, N.; Sivula, K. J. Mater. Chem. A 2016, 4, 3018-3026.

[2] Yu, X.; Prevot, M. S.; Guijarro, N.; Sivula, K., Nat. Commun. 2015, 6, 7596.

[3] Yu, X.; Rahmanudin, A.; Jeanbourquin, X. A.; Tsokkou, D.; Guijarro, N.; Banerji, N.; Sivula, K. ACS Energy Lett. 2017, 2, 524.

[4] Bornoz, P.; Prévot, M. S.; Yu, X.; Guijarro, N.; Sivula, K. J. Am. Chem. Soc. 2015, 137, 15338.