SPR-Active Surfaces for Broadband Solar Energy Coupling
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Solution Overview
Problem
Current photocatalytic systems face inefficiencies due to limited overlap between solar wavelengths and optimal excitation wavelengths, particularly in semiconductor-based systems like bulk TiO2, which absorbs mainly in the ultraviolet range, thereby utilizing only a small percentage of solar energy.
Innovation Solution
The development of SPR-enhanced photocatalytic systems that utilize angular dispersion of incident light to couple into angle-dependent SPR-active surfaces, such as GCSPR, Kretschmann, and EOSPR configurations, allowing for broadband coupling of light energy into surface plasmon modes, which is then transferred to photocatalysts for enhanced chemical reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If semiconductor-based photocatalytic systems (e.g., bulk TiO2) are used, then catalytic activity is achieved, but the utilization of solar energy is limited due to absorption mainly in the ultraviolet range
Solution Approach 1:
The patent combines semiconductor photocatalysts with metallic nanostructures exhibiting localized surface plasmon resonance (LSPR) to create a composite system. The metal component (e.g., Au, Ag, Al) absorbs visible light and transfers energy to the semiconductor, enabling the system to utilize both UV and visible portions of the solar spectrum, thereby resolving the contradiction between achieving catalytic activity and maximizing solar energy utilization
Solution Approach 2:
The patent modifies the optical properties of the photocatalytic system by introducing plasmonic metals with different band structures and plasmon resonance characteristics. By selecting metals with appropriate plasma frequencies and adjusting their morphology (nanoparticles, nanorods, shells), the system can be tuned to absorb specific wavelengths in the visible range, thus expanding solar energy utilization while maintaining catalytic efficiency
2Productivity
If the excitation wavelength of the catalyst is optimized for maximum catalytic activity, then catalytic efficiency is improved, but the overlap with solar wavelength spectrum is reduced
Solution Approach 1:
The plasmonic metal acts as an intermediary that absorbs visible light (which the semiconductor cannot absorb efficiently) and transfers the energy to the semiconductor photocatalyst. This intermediary mechanism enables the system to utilize solar wavelengths that do not directly excite the semiconductor, thereby expanding solar spectrum coverage while maintaining high catalytic efficiency through the semiconductor's optimized band structure
3Stability of the object's composition
If bulk semiconductor materials are used, then material stability is achieved, but the absorption of visible light is poor
Solution Approach 1:
The patent creates a composite where the stable bulk semiconductor provides structural stability and catalytic active sites, while dispersed metallic nanoparticles provide visible light absorption through LSPR. This composite structure allows the system to maintain the stability of the bulk semiconductor while gaining visible light absorption capability from the plasmonic metal component
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient conversion of incident light energy into photocatalytic activity, capturing a large portion of the solar spectrum and improving catalytic efficiency by optimizing the angle and intensity of incident light to match resonance conditions, thereby enhancing reaction rates and energy utilization.
Implementation Method 1
surface plasmon resonance is achieved when P-polarized light couples into a charge density oscillation at a metal-dielectric interface
Implementation Method 2
Localized surface plasmon resonance has been explored extensively for a diverse range of applications and has been incorporated into a variety of photocatalytic systems
Implementation Method 3
Grating-coupled surface plasmon resonance circumvents some of the cost, size, and logistical limitations of the Kretschmann configuration
Implementation Method 4
photocatalytic splitting of water has been investigated as a source for clean and renewable hydrogen
Implementation Method 5
Transfer of photonic energy from the excited plasmon to one or more materials with photocatalytic activity
Implementation Method 6
the role of metallization and the importance of the Schottky barrier in preventing electron-hole recombination
Implementation Method 7
Angular dispersion of incident light onto an SPR-active surface, so that each incident wavelength will strike the surface at a range of angles and relative intensities that approximate the resonance curve
Data Source
AI summary
Plasmonically-enhanced catalytic surfaces and accompanying optics are described herein. These elements facilitate efficient coupling of light energy into a photocatalytic system by way of a surface plasmon. Various compatible optical configurations are presented, with an emphasis on the broadband coupling of light into a single plasmon mode. In an example embodiment, dispersive optics are used to direct polychromatic light onto a grating-embossed SPR-active surface. Dispersive optics allow resonance to be achieved at a wide range of incident wavelengths. Energy then transfers from the excited plasmon to an adjacent photocatalyst. The plasmon mode thus acts as a “funnel” of broadband light energy to the catalytic materials. High-efficiency incoupling and outcoupling from the plasmon mode suggest overall enhancement of catalytic activity, and broad applicability is anticipated due to the inherent flexibility of the system. The catalytic surfaces and optical components can be fabricated as sheets or 3D arrays, justifying industrial-scale manufacturing.