Ga Selenide Photocatalyst Band Gap Engineering

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Solution Overview

Problem

Current photocatalysts for water splitting, such as Cu-based chalcopyrite materials, have insufficient water splitting activity due to their band gap positioning, which fails to effectively sandwich the reduction and oxidation potentials of water, limiting hydrogen production efficiency.

Innovation Solution

A photocatalyst comprising Ga selenide, Ag-Ga selenide, or both, with a higher valence band maximum positioning, allowing for higher water splitting activity, and optionally incorporating Rh or Pt as promoters to enhance reaction rates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If Cu-based chalcopyrite materials are used as photocatalysts, then the band gap can be controlled by changing composition, but the valence band maximum is too low to achieve sufficient water splitting activity

Engineering Contradiction:

Improveband gap controlVSAvoidwater splitting activity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters by substituting Cu with Ag in the chalcopyrite structure, forming Ag(In,Ga)(Se,S)2 materials. This parameter change raises the valence band maximum to achieve proper positioning for water splitting while maintaining controllable band gap through composition adjustment.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates composite materials by combining multiple elements (Ag, In, Ga, Se, S) in a chalcopyrite structure. The composite nature allows simultaneous optimization of band gap for light absorption and valence band position for water oxidation, resolving the contradiction between adaptability and reliability.

Inventive Principle:

Principle #40Composite materials

2Ease of operation

If conventional photocatalysts are used for water splitting, then the process can proceed without external voltage, but the hydrogen production efficiency is limited due to insufficient water splitting activity

Engineering Contradiction:

Improveoperation simplicityVSAvoidhydrogen production efficiency

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The patent optimizes the electronic structure parameters of the photocatalyst by adjusting the Ag/(In+Ga) ratio and Se/S composition. These parameter changes enhance water splitting activity and hydrogen production efficiency while maintaining the simplicity of operation without external voltage.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the valence band maximum is increased to improve water splitting activity, then hydrogen production efficiency increases, but the band gap positioning may shift away from optimal light absorption range

Engineering Contradiction:

Improvewater splitting activityVSAvoidlight absorption efficiency

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The patent employs composite chalcopyrite materials with multiple variable components (Ag, In, Ga, Se, S) that allow independent optimization of band gap and valence band position. The composite structure provides sufficient degrees of freedom to simultaneously achieve optimal light absorption and high water splitting activity.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent utilizes composition parameter changes to decouple the optimization of band gap and valence band maximum. By adjusting the ratio of different elements, the patent achieves proper band gap positioning for light absorption while simultaneously raising the valence band maximum for efficient water splitting.

Inventive Principle:

Principle #35Parameter changes

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 use of Ga selenide and Ag-Ga selenide photocatalysts with optimized band gap positioning achieves higher water splitting activity and hydrogen production, potentially reducing the need for external voltage in the water splitting reaction.

Implementation Method 1

a photocatalyst capable of splitting water using a natural energy such as sunlight to produce hydrogen

Methodology Applied

Scientific EffectPhotocatalysis:

Implementation Method 2

the at least one semiconductor region is of Group III-VI and is selected from the group consisting of InSe, InTe, InS, GaSe

Methodology Applied

Scientific EffectPhoton absorption: Absorption (EM radiation)

Data Source

PatentUS9975115B2Photocatalyst for water splitting comprising gallium selenide and photoelectrode for water splitting comprising the same

Publication Date: 2018.05.22 TOYOTA JIDOSHA KK

AI summary

Provided are a photocatalyst having higher activity for hydrogen production through water splitting and a photoelectrode comprising the photocatalyst. The photocatalyst for water splitting of the present invention comprises a Ga selenide, an Ag—Ga selenide, or both thereof.