A key challenge for the development of materials and technologies for solar-to-fuels energy conversion lies in resolving structure, structural dynamics, and mechanisms underlying solar fuels catalysis, and measuring these structural parameters during functional conditions. Our research programs investigate mechanisms for coupling light-generated excited states to charge accumulation and multi-electron fuels catalysis in materials that span the range from photosynthetic proteins to artificial photosynthesis. This presentation will highlight our work on biomimetic designs for solar energy conversion and also recent work on the development of synchrotron X-ray techniques for in-situ structure-function characterization of solar fuels catalysts. In particular, this presentation will discuss examples of the use of high energy X-ray scattering and atomic pair distribution function (PDF) analysis for characterization of amorphous thin film and molecular water-oxidation catalysts, and for resolving metal-oxo coordination chemistry during electrocatalytic water-splitting. The PDF technique offers an opportunity to resolve atomic pair correlations across the full inner and outer shell coordination spheres for transition metal complexes with 0.2 Å spatial resolution. This level of precision is sufficient to develop explicit coordinate models. We are developing PDF techniques as in-situ approaches for investigation of photochemical processes for both homogeneous and interfacial, electrode-supported, solar-driven water splitting and fuels catalysis. We have extended the in-situ PDF technique by developing 3-D porous electrode architectures based on microchannel arrays ALD coated with conductive ITO layers that enable structural characterization of interfacial thin films of first row transition metal oxides during photo-electrochemical function. With these porous electrode architectures, we find that are able to carry out high resolution PDF analysis for amorphous oxide catalyst thin films with thickness below 70 nm and under active electrochemical control. This work will show opportunities to use in-situ X-ray PDF approaches to achieve atomic scale characterization of both heterogeneous and molecular catalysts during photochemical function with applications in natural and artificial photosynthesis.

Biomimetic designs and In-Situ x-ray structural characterization of catalysts for the artificial leaf

253rd National Meeting (2017)

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