Nitride Semiconductor Photoelectrode for CO2 Reduction

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Solution Overview

Problem

Existing methods for reducing carbon dioxide using photoelectrodes face inefficiencies due to carrier recombination and the need for external power sources, limiting the effectiveness of carbon dioxide reduction reactions.

Innovation Solution

A photoelectrode with a nitride semiconductor layer structure, comprising a first aluminum gallium nitride layer, a second aluminum gallium nitride layer with a variable composition ratio, and a gallium nitride layer, is used to reduce carbon dioxide efficiently without an external power source, by irradiating the anode electrode with light of 360 nm or less, thereby minimizing carrier loss and enhancing reaction efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a photoelectrode is used to reduce carbon dioxide by light energy, then carbon dioxide reduction is achieved, but carrier recombination occurs leading to reduced efficiency

Engineering Contradiction:

Improvecarbon dioxide reduction efficiencyVSAvoidcarrier recombination loss

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The photoelectrode is segmented into multiple functional layers: a light-absorbing layer containing a semiconductor and carbon dioxide reduction catalyst, a hole transport layer containing a hole transport catalyst, and optionally a buffer layer. This segmentation separates the functions of light absorption, charge separation, and catalytic reduction, preventing carrier recombination and improving overall efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The photoelectrode employs composite material structures combining semiconductors (such as TiO2, ZnO, GaN) with metal catalysts (such as Pt, Pd, Au, Cu, Ni) and organic hole transport materials. These composite structures create optimal interfaces for charge separation and transfer, reducing carrier recombination losses while enhancing carbon dioxide reduction activity.

Inventive Principle:

Principle #40Composite materials

2Productivity

If an external power source is used in combination with light irradiation to reduce carbon dioxide, then reduction reaction is enhanced, but device complexity and energy input requirements increase

Engineering Contradiction:

Improvecarbon dioxide reduction rateVSAvoidpower source requirement

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The photoelectrode system is designed to be self-sufficient by utilizing only light energy input. The photoelectrode material itself generates the necessary electrons through photoexcitation and provides built-in catalytic sites for carbon dioxide reduction, eliminating the need for external power sources while maintaining high reduction rates.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention optimizes the band gap energy, catalyst particle size, and surface area of the photoelectrode to maximize light absorption efficiency and charge carrier generation. By adjusting these parameters, the system achieves sufficient reduction rates using only light energy without requiring additional electrical power input.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a simple photoelectrode structure is used, then device complexity is reduced, but carrier loss increases and reduction efficiency decreases

Engineering Contradiction:

Improvephotoelectrode structureVSAvoidcarrier loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A hole transport layer containing a hole transport catalyst (such as Ru complexes, Os complexes, or organic dyes) is introduced as an intermediary between the semiconductor and the electrolyte. This intermediary facilitates efficient hole extraction and transport, preventing electron-hole recombination while maintaining structural simplicity.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 significantly improves the efficiency of carbon dioxide reduction by reducing carrier loss at the anode electrode and increasing the supply of carriers to the cathode electrode, resulting in higher yields of reaction products such as formic acid, carbon monoxide, and hydrocarbons.

Implementation Method 1

a photoelectrode used to reduce carbon dioxide by light energy

Methodology Applied

Scientific EffectPhotoexcitation: Photosynthesis

Implementation Method 2

reduce carbon dioxide by light energy alone and without using an external power source

Methodology Applied

Scientific EffectPhotoelectrochemical reduction: Photovoltaic Effect

Data Source

PatentUS9551077B2Photoelectrode used for carbon dioxide reduction and method for reducing carbon dioxide using the photoelectrode

Publication Date: 2017.01.24 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

Disclosed is an anode electrode including a nitride semiconductor layer. This nitride semiconductor layer includes an AlxGa1-xN layer (0<x≦0.25), an AlyGa1-yN layer (0≦y≦x), and a GaN layer. The AlyGa1-yN layer is interposed between the AlxGa1-xN layer and the GaN layer. The value of x is fixed in the thickness direction of the AlxGa1-xN layer. The value of y decreases from the interface with the AlxGa1-xN layer f toward the interface with the GaN layer. The AlxGa1-xN layer is irradiated with light having a wavelength of 360 nm or less so as to reduce carbon dioxide.