HotElecTEM · In-Depth Dynamical Structural and Optical Study of Unconventional Au Based Plasmonic Core@ Catalytic Shell Antenna-Reactor System by Electron Microscopy and Simulations

In-Depth Dynamical Structural and Optical Study of Unconventional Au Based Plasmonic Core@ Catalytic Shell Antenna-Reactor System by Electron Microscopy and Simulations

Global energy demand grew by 2.2% in 2024, a notably faster rate than the annual average of 1.3% seen between 2013 and 2023. Fossil fuels have 80% contribution in this production which alarmingly increases the amount of CO2 in the environment. Sunlight is a renewable energy source and an efficient use of it can lower the CO2 level significantly. Ni-based photocatalysts is showing a great efficiency with very good reproducibility, however a surge in the electric vehicle (EV) production is making Ni more valuable and it is predicted that within 2025 the global demand for Ni will exceed the supply making it a scarce material. Hence an alternate material is urgently needed and plasmonic noble metal nanoparticles (NMN) have shown a great potential in this aspect. Upon excitation with external electromagnetic wave, plasmonic NMN can produce hot electrons (e-) and holes (h+), which can drive reactions at the nanoparticle surface. This incredible phenomenon can make NMN a potential replacement of fossil fuels and Ni-based catalysts for different energy application. Besides, use of NMN for photocatalysis will also reduce the CO2 emission in the atmosphere, which is an urgent need for the globe in current scenario. However, single component NMN shows a high e--h+ recombination rate making the system less efficient. They also show a deteriorated behavior when they are subjected to high temperature, repetitive I-V cycles during the energy production reaction which prevents production of large-scale industrial devices containing these structures. Multicomponent hybrid nanomaterials provided a paradigm shift in this aspect. In these systems, the plasmonic core acts as the energy concentrator and the shell material extracts the energy in the form of electronic excitation. Bi-metallic nanoparticles combination of Au-Pd/Pt, Ag-Pt (in face centered cubic (fcc) phase) showed great potential to be commercial photocatalyst. All these prompts make this material quite promising; however, during the catalysis process, nanomaterials containing 3H-HCP (hexagonal closed packed) or fcc Au lost the size, shape and plasmonic efficiency. So, finding a stable configuration with intense plasmon resonances at lower energies and of significant lifetime is still an open challenge and is urgent considering the global energy crisis for their applications in photocatalysis and photothermal reactions. In HotElecTEM, our aim is to find out the best conditions to obtain an efficient, robust bi-metallic systems for photocatalytic and photothermal applications. We will use unconventional 4H(2H)-HCP Au core instead of conventional 3H-HCP Au core as fcc configuration does not provide a stable mechanical property at high temperatures (beyond 300-400K) contributed by high ductility and low stacking fault energy. In HotElecTEM, we will synthesize composite consisting of 4H-HCP Au triangular nanoparticle (AuTNP) as the core and metal as catalytic shell to investigate the optical properties, especially hot-e- generation and transfer efficiency experimentally using low-energy electron-energy loss spectroscopy (EELS) in a state-of-the-art aberration corrected TEM (Ac-TEM) at LMA, UNIZAR, Spain and also theoretically using molecular dynamics and light-matter interaction simulation. In-situ thermal, plasmonic and structural stability of single and bi-metallic Au core and catalytic shell (metal) composite will be investigated using in-situ heating/cooling and biasing experiment in TEM. The specific objectives defined to achieve HotElecTEM’s main goal are: Objective (O1): Production of Au triangular nanoparticle’s (AuTNP) and core@shell AuTNP@Pd/graphene composite with 4H-HCP (2H-HCP) configuration and optimization for enhanced optoelectronics and mechanical properties of the synthesis procedure to obtain a high-yield of the nanoparticles. Objective (O2): Experimentally reveal structural and (opto)electronic properties of hybrid materials by electron microscopy and spectroscopy techniques. Objective (O3): Unravel response and properties of the nanomaterials to external stimuli (heating/cooling and biasing) by in-situ electron microscopy. Objective (O4): Obtain structure and (opto)electronic properties of the identical nanomaterials by conducting computational studies (via models) congruent with the experiments Successful implementation of this project possesses a long-term effect on the development of low-cost sustainable photocatalyst, SERS based sensors and plasmonic-based solar cells. It has the potential to replace fossil fuel and Ni based catalysts, which are getting scarce and valuable day by day and this project has the potential to pave the way. As plasmonic catalysts has the potential to replace fossil fuels, it will lead to decrement in the CO2 and other greenhouse gas emission, which is now a global problem and is vastly compatible with “Fit for 55” EU climate policy, the objective of which is to become first climate neutral continent by 2050. Also, integration of unconventional plasmonic nanostructure in photovoltaic Solar cells can increase the efficiency significantly, making the societal impact of the project really vast.

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