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Sustainable plasmon-enhanced catalysis

Periodic Reporting for period 1 - SPECs (Sustainable plasmon-enhanced catalysis)

Reporting period: 2019-01-01 to 2020-06-30

Industries creating inorganic, organic, and agricultural chemicals use a staggering 4.2% of the worldwide delivered energy, mainly from unsustainable fossil fuels. Meanwhile, the sun provides energy that could be utilized to power photochemical reactions sustainably and cleanly. Recent advances revealing how localized surface plasmon resonances (LSPRs), light-driven electron oscillations in metal nanoparticles, can concentrate light at the molecular scale made the dream of efficient photochemistry one step closer. However, plasmonic materials are almost exclusively constructed from the rare and unsustainable metals Ag and Au. In addition to being incompatible with current industrial practices relying on catalytic surfaces to lower energy barriers and guide reactions, Ag and Au cause prohibitive cost challenges for real-world applications. But there is hope: several of the few metals predicted to sustain LSPRs and become potential alternatives to Ag and Au are amongst the most abundant, i.e. sustainable, elements on Earth (Al, Mg, Na, K).
The way forward, and key objective of this project, is to design, synthesize, and understand multimetallic nanostructures where a cheap, Earth-abundant plasmonic material traps and concentrates (sun)light directly at a catalytic surface to efficiently and intelligently power and choreograph chemical reactions. To achieve this ambitious goal, the team is concurrently advancing important aspects of sustainable plasmon-enhanced catalysis, from the development of synthetic approaches for Earth-abundant plasmonic-catalysts, to the fundamental studies of light-trapping in these new materials with state-of-the-art numerical and experimental approaches and the unravelling of the relative contribution of plasmon-generated hot electrons, enhanced field, and heat using key model chemical reactions. These results will help develop a more sustainable future by lowering our reliance on both fossil fuels and rare metals.
The reporting period covers the first year and a half of the project, where one new post-doctoral research associate started (Jan 2019) and one new PhD student started (Oct 2019). So far we have made important advances in the understanding of the crystallography, decoration, and plasmonic properties of Mg nanoparticles.
We developed the electrochemical cell to deposit Cu on Au decahedra at different rates, and acquired coating thickness statistics on single nanoparticles, toward controllable synthesis of bimetallics using electrodeposition (WPA). Earth-abundant structures have been synthesized and investigated (WPB): the study of plasmonic properties in single crystal and singly twinned Mg NPs led to a publication in ACS Nano (Asselin, Boukouvala et al, 2020). Further, we achieved galvanic replacement of noble elements (Au, Ag, Pd, Fe) on Mg to produce bi- or multimetallic particles (Asselin et al, J. Phys. Chem., 2019). In WPC, we advanced the understanding and numerical approaches to predict shapes in Mg NPs and anticipate their LSPR properties (Boukouvala and Ringe, J. Phys. Chem. C, 2019). In addition, we have characterised single-particle scattering for bare and decorated Mg (WPB), and correlated these optical signatures with the numerical results (Asselin, Boukouvala et al, 2020). Advances in WPD and WPE include the synthesis of polydopamine-coated Mg nanoparticles that are stable in water, and the purchase of a GC-MS system for catalytic studies, respectively. Unfortunately the most Covid-affected area of research is WPE, as the PDRA hired for this saw his start date delayed from March to September 2020 due to the department closure and personal circumstances.
In the remainder of the project, the team aims to explore new compositions of plasmonic nanostructures, their controlled decoration, and their catalytic properties. Our aim is to make progress on the design, synthesis, and understanding of multimetallic nanostructures where a cheap, Earth-abundant (i.e. sustainable) plasmonic material traps and concentrate light, eventually sustainable sunlight, directly at a catalytic surface to efficiently and intelligently power and choreograph chemical reactions. We aim to further expand plasmonics towards Mg, Na, and K, all predicted to be better than Al and nearly as good as Au, but orders of magnitude less expensive than the latter. We also aim to perform electrodeposition to controllably deposit thin layers of metals, and catalytic experiments on the resulting plasmonic structures.
Summary of the synthetic and characterization advances on the Earth-Abundant Mg plasmonic NPs