Doped TiO2 Photocatalyst for Visible Light Absorption
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Solution Overview
Problem
Current photocatalysts, particularly titanium dioxide (TiO2), are limited in their ability to degrade organic pollutants under visible light due to their large band gap, making them inactive in indoor conditions and poorly illuminated areas, and existing modifications often result in reduced stability and efficiency.
Innovation Solution
Development of doped TiO2 photocatalysts using environmentally friendly methods with renewable sources, incorporating metal and non-metal dopants like nitrogen, silver, bismuth, and sulfur, which are synthesized through in-situ sol-gel methods to enhance stability and reactivity under visible light, allowing for broader solar spectrum utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If TiO2 is used as a photocatalyst under UV irradiation, then high reactivity and chemical stability are achieved, but it remains inactive under visible light and solar illumination comprising less than 5% of solar energy is utilized
Solution Approach 1:
The patent applies parameter changes by doping TiO2 with nitrogen and silver, which modifies the electronic structure and band gap of the material. This chemical composition change enables the photocatalyst to absorb visible light wavelengths that pristine TiO2 cannot utilize, thereby expanding solar spectrum utilization from less than 5% to a significantly broader range including visible light portions.
Solution Approach 2:
The patent creates a composite material system by combining TiO2 with nitrogen-doped components and silver particles. This composite structure leverages the complementary properties of each component: TiO2 provides chemical stability and UV photocatalytic activity, nitrogen doping extends visible light absorption, and silver enhances electron-hole separation and visible light responsiveness, achieving synergistic photocatalytic performance under both UV and visible light.
2Use of energy by moving object
If TiO2 is doped with nitrogen-containing compounds to extend light absorption into visible range, then visible light activation is achieved, but stability and efficiency are reduced
Solution Approach 1:
The patent merges multiple doping approaches by combining nitrogen doping with silver deposition on TiO2. The nitrogen doping extends visible light absorption while silver particles provide electron trapping sites that prevent recombination of electron-hole pairs. This combination compensates for the stability and efficiency losses associated with nitrogen doping alone, as silver reinforces the structural stability and maintains high photocatalytic efficiency under visible light irradiation.
3Productivity
If metal dopants are used to extend light absorption and act as electron traps, then electron-hole separation is enhanced, but photocatalytic activity in UV range is reduced
Solution Approach 1:
The patent applies local quality by distributing silver particles selectively on the TiO2 surface rather than uniformly doping throughout the bulk material. This localized surface modification allows silver to function as electron traps at critical surface sites where electron-hole recombination occurs, enhancing separation efficiency. Meanwhile, the bulk TiO2 structure and its UV absorption properties remain largely intact, preserving UV photocatalytic activity while adding visible light responsiveness at the surface.
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
The doped TiO2 photocatalysts demonstrate high stability and reactivity under artificial and solar visible light, enabling effective degradation of organic compounds in gases, liquids, and on surfaces, even in poorly illuminated areas, with recyclability and enhanced synergistic activity compared to individual dopants.
Implementation Method 1
Nitrogen atoms have attracted the most attention because its p state contributes to the band gap narrowing by mixing with the oxygen 2p states
Implementation Method 2
Metal dopants affect the surface properties by generating a Schottky barrier of the metal in contact with TiO2 surface, which acts as an electron trap and inhibits e−-h+ recombination
Implementation Method 3
The doped TiO2 photocatalysts demonstrate high stability and reactivity under artificial and solar visible light, enabling effective degradation of organic compounds
Data Source
AI summary
Methods for preparing and using a photocatalyst are described. The catalyst is prepared by oxidation of a metal salt which has been doped in situ to form a photocatalyst active in visible light. The photocatalyst is used for degrading toxic and irritating compounds and infectious agents.