Doped Titania Photocatalysts Visible Light Synthesis
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Solution Overview
Problem
Titanium dioxide (TiO2) photocatalysts are ineffective under visible light due to a large band gap, limiting their application in indoor settings and areas with minimal UV light, despite efforts to modify their photocatalytic activity through doping, which often results in unstable or UV-light-dependent performance.
Innovation Solution
A mechanochemical process using a planetary ball mill with zirconia balls and controlled temperature to synthesize Au or Au/Ag doped titania nanoparticles, optimizing milling speed, time, and dopant dosage to enhance photocatalytic activity under visible light, maintaining the anatase crystal phase and preventing agglomeration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If titanium dioxide is doped with nitrogen-containing compounds or other compounds to modify photocatalytic activity, then the photocatalytic activity is enhanced, but the stability and efficiency are limited and the catalyst remains active only under UV light
Solution Approach 1:
The patent changes the fundamental parameter of light absorption by doping TiO2 with noble metals (Au, Ag, Pt, Pd) that introduce new electronic states and reduce the band gap, enabling visible light absorption. This parameter change transforms the catalyst from UV-only activation to visible light activation, resolving the contradiction between enhanced activity and limited stability under UV light.
Solution Approach 2:
The patent creates composite materials by combining TiO2 with noble metal nanoparticles (Au, Ag, Pt, Pd) through photo-deposition. This composite structure allows the TiO2 to provide structural stability and the noble metals to provide visible light absorption, achieving both enhanced photocatalytic activity and improved stability under visible light conditions.
2Illumination intensity
If conventional doping methods are used to decrease the band gap of TiO2, then visible light activation is achieved, but long synthesis time and calcination are required which cause agglomeration
Solution Approach 1:
The patent replaces traditional thermal processing methods (calcination) with a photochemical method (photo-deposition). Instead of using high temperature and long synthesis times to dope TiO2, the invention uses UV irradiation to directly deposit noble metal nanoparticles onto the TiO2 surface, dramatically reducing synthesis time and avoiding agglomeration caused by prolonged heating.
Solution Approach 2:
The patent performs preliminary action by first depositing the noble metal nanoparticles onto the TiO2 surface through photo-deposition before any potential agglomeration can occur. This preliminary doping step creates a stable composite structure that can then be used directly for visible light photocatalysis without requiring subsequent high-temperature treatment.
3Adaptability or versatility
If titanium dioxide is used in indoor areas with no UV light, then the application scope is expanded, but photocatalysis does not occur because UV light is not present
Solution Approach 1:
The patent fundamentally changes the light absorption parameter of TiO2 by introducing noble metal dopants that create new electronic transitions in the visible region. This parameter change enables the catalyst to respond to visible light wavelengths (400-700 nm) present in indoor environments, expanding its applicability from outdoor UV-exposed areas to indoor visible light environments.
Solution Approach 2:
The patent makes TiO2 universally applicable to both outdoor and indoor environments by赋予 it dual functionality: maintaining its original UV photocatalytic activity while adding visible light photocatalytic activity through noble metal doping. This multi-functionality allows the same material to be used in diverse lighting conditions, from sunlight-rich outdoor areas to artificial light indoor areas.
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 titania nanoparticles exhibit higher photocatalytic activity under visible light, with 70-90% degradation of methyl orange within 3 hours, surpassing commercial titania performance and maintaining stability without calcination-induced agglomeration.
Implementation Method 1
A mechanochemical process using a planetary ball mill with zirconia balls and controlled temperature to synthesize Au or Au/Ag doped titania nanoparticles
Implementation Method 2
The doped titania nanoparticles exhibit higher photocatalytic activity under visible light, with 70-90% degradation of methyl orange within 3 hours
Implementation Method 3
titanium dioxide is a photocatalyst which is active under ultraviolet (UV) light... The doped titania nanoparticles exhibit higher photocatalytic activity under visible light
Data Source
Figure 1(a)~1(b)
Figure 1(c)~1(d)
Figure 2~3
AI summary
Present disclosure provides a process for the synthesis of visible light responsive doped titania photocatalysts. The process involves step a) milling a mixture containing titania and a precursor compound, said compound selected from the group consisting of chloroauric acid and a mixture containing chloroauric acid and silver nitrate, in the presence of water and oxide milling media, at a temperature in the range of 20 to 50°C for a period of 60 -120 minutes, to form a slurry, wherein the amount of water is in the range of 15 to 25% by weight of the total mixture; and b) filtering the slurry to separate the oxide milling media and obtain a filtrate containing doped titania nanoparticles.