(544gd) Advanced Laser-Made Nanocatalysts for Solar Water Splitting

Conversion of solar energy into storable fuels is key to meet future energy demands. New materials that are efficient, robust, and exclusively made of non-precious elements are essential for a sustainable energy economy. We used pulsed-laser in liquids synthesis to prepare novel nanomaterials for solar water splitting applications. The method is a flexible synthetic strategy for surfactant-free nanomaterials with controlled compositional, morphological, and structural properties.

Water oxidation is a key chemical transformation for the conversion of solar energy into storable fuels.¹ Our laser-made Co₃O₄ nanocrystals had an electrocatalytic activity that compared favorably to the best reported cobalt oxides.² Multi-metal nanomaterials with tailored compositions were readily prepared by adding metal ions into the aqueous liquid; our approach allowed the rapid optimization of highly active, robust nickel–iron layered double hydroxide nanocatalysts for water oxidation in base.³ Structural analysis of these mixed-metal catalysts showed that water oxidation occurred at edge-site iron centers. Interlayer anions played key roles during turnover, as incorporating anions with different basicities tuned the catalytic performance of these materials; overpotentials depended sigmoidally on anion basicity, suggesting a base-assisted water-oxidation mechanism. Our nanocatalysts were regenerated and most active in alkaline electrolyte in ambient air, where ubiquitous carbonate rapidly replaced other interlayer anions.⁴ We gained structural and mechanistic insights from in-situ spectroscopy data: we identified a cis-dioxo iron(VI) reactive intermediate as the lowest-energy species before O–O bond formation during water oxidation catalysis.⁵ And we optimized photocurrent generation of integrated laser-made nanocatalyst photoanodes by rational design.⁶

References:

[1] Hunter, B. M.; Gray, H. B.; Müller, A. M. Chem. Rev. 2016, 116, 14120.

[2] Blakemore, J. D.; Gray, H. B.; Winkler, J. R.; Müller, A. M. ACS Catal. 2013, 3, 2497.

[3] Hunter, B. M.; Blakemore, J. D.; Deimund, M.; Gray, H. B.; Winkler, J. R.; Müller, A. M. J. Am. Chem. Soc. 2014, 136, 13118.

[4] Hunter, B. M.; Hieringer, W.; Winkler, J. R.; Gray, H. B.; Müller, A. M. Energy Environ. Sci. 2016, 9, 1734.

[5] Hunter, B. M.; Thompson, N. B.; Müller, A. M.; Rossman, G. R.; Hill, M. G.; Winkler, J. R.; Gray, H. B. Joule 2018, 2, 1.

[6] Sinclair, T. S.; Gray, H. B.; Müller, A. M. Eur. J. Inorg. Chem. 2018, 2018, 1060.