Photocatalyst Semiconductor Junction Layout for Charge Separation
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Solution Overview
Problem
Existing photocatalytic systems face low quantum yield and inefficiencies due to uncontrolled spatial separation of electron-hole pairs and reverse reactions, particularly in systems involving gaseous reactions with solid electrodes.
Innovation Solution
A semiconductor device with a semiconductor layer coated by oxidation and reduction catalyst layers forming Schottky and ohmic junctions, respectively, and an insulation layer to prevent deterioration, facilitating efficient spatial separation and movement of charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metal fine particles are coated on the surface of titanium oxide particles to facilitate hydrogen production, then the reduction reaction is improved, but the oxidation and reduction sites are not spatially separated, causing reverse reactions
Solution Approach 1:
The device divides the photocatalyst surface into distinct oxidation reaction sites and reduction reaction sites that are spatially separated. Titanium oxide particles serve as the photocatalyst base, with oxidation catalysts positioned at specific locations and reduction catalysts at other locations, ensuring that electron-hole pairs are separated into different spatial zones to prevent reverse reactions.
Solution Approach 2:
Different regions of the photocatalyst surface are assigned different functional qualities: oxidation reaction sites are equipped with oxidation catalysts (such as metal oxides) to facilitate water oxidation, while reduction reaction sites are equipped with reduction catalysts (such as noble metals) to facilitate proton reduction. This local differentiation ensures that each site performs its specific function efficiently while maintaining spatial separation.
2Reliability
If oxidation and reduction reaction sites are provided in a separated manner using electrically connected plates, then electron-hole separation is improved, but the system becomes complex and requires electrolyte systems with ion exchange membranes
Solution Approach 1:
The device merges the photocatalyst support function and the reaction site separation function into a single integrated structure. Titanium oxide particles serve as both the photocatalyst material and the structural framework that holds both oxidation and reduction catalysts in spatially separated positions. This integration eliminates the need for separate electrically connected plates and ion exchange membranes, simplifying the overall system while maintaining effective electron-hole separation.
3Ease of manufacture
If the entire surface of titanium oxide particles is coated with a single catalyst layer, then manufacturing is simplified, but spatial control of reaction sites is lost
Solution Approach 1:
The device incorporates reaction site patterning into the catalyst layer formation process itself. During the coating process, oxidation catalysts and reduction catalysts are deposited in predetermined spatial arrangements directly onto the titanium oxide particle surfaces. This preliminary arrangement of catalysts in specific patterns ensures that when the device operates, electrons and holes are automatically directed to the correct reaction sites without requiring additional complex assembly steps.
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
Improves quantum yield and suppresses deterioration reactions, enabling efficient production of hydrogen and oxygen without significant reverse reactions.
Implementation Method 1
a semiconductor layer disposed on a surface of a substrate and causing an oxidation reaction and a reduction reaction when irradiated with light
Implementation Method 2
an oxidation catalyst layer that is disposed on part of a surface of the semiconductor layer, forms along with the semiconductor layer a Schottky junction, and oxidizes an oxidation target substance
Implementation Method 3
a reduction catalyst that is disposed on part of the surface of the semiconductor layer where the oxidation catalyst layer is not disposed so as to be separated from the oxidation catalyst layer, forms along with the semiconductor layer an ohmic junction, and reduces a reduction target substance
Data Source
AI summary
A semiconductor device includes a semiconductor layer, which is disposed on the surface of a substrate and causing an oxidation reaction and a reduction reaction when irradiated with light, an oxidation catalyst layer, which is disposed on part of the surface of the semiconductor layer, forms along with the semiconductor layer a Schottky junction, and oxidizes an oxidation target substance, a reduction catalyst layer, which is disposed on part of the surface of the semiconductor layer where the oxidation catalyst layer is not disposed so as to be separated from the oxidation catalyst layer, forms along with the semiconductor layer an ohmic junction, and reduces a reduction target substance, and an insulation layer, which is disposed on the entirety of the surface of the semiconductor layer where none of the oxidation catalyst layer and the reduction catalyst layer is disposed so as to be in contact with the oxidation catalyst layer and the reduction catalyst layer.