Cathode Strontium Sulfate Coverage Reduces Polarization

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Solution Overview

Problem

In solid oxide fuel cells and electrolysis cells, strontium (Sr) from the cathode can diffuse into the electrolyte layer, reacting with elements to form high-resistance layers, which deteriorate power generation performance, despite the use of intermediate layers to prevent such reactions.

Innovation Solution

The electrochemical reaction unit cell incorporates a cathode with an active layer containing strontium-containing perovskite oxide, second cerium oxide, and strontium sulfate, where strontium sulfate forms and covers the second cerium oxide, reducing the area of strontium sulfate coverage on the perovskite oxide, thereby minimizing activation polarization and preventing high-resistance layer formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an intermediate layer is disposed between the cathode and the electrolyte layer to prevent Sr diffusion, then formation of high-resistance layer is prevented, but Sr may still diffuse into the intermediate layer and react with elements to form high-resistance layer, deteriorating power generation performance

Engineering Contradiction:

Improvepower generation performanceVSAvoidintermediate layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent introduces a second intermediate layer containing GDC and sulfur between the first intermediate layer (GDC) and the cathode. This second intermediate layer acts as an additional mediator to prevent Sr diffusion into the first intermediate layer, thereby preventing formation of high-resistance SrZrO3 layer while maintaining the protective function of the original intermediate layer structure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a composite intermediate layer structure where the second intermediate layer contains GDC and sulfur in specific proportions (0.1-10 wt% sulfur). This composite material approach allows the layer to simultaneously provide ion conductivity (from GDC) and Sr diffusion barrier function (from sulfur-containing compounds), resolving the contradiction between reliability and structural complexity

Inventive Principle:

Principle #40Composite materials

2Reliability

If Sr reacts with S and oxygen to form SrSO4 in the cathode active layer, then diffusion of Sr to the electrolyte layer is prevented, but SrSO4 is an insulating substance that covers the perovskite oxide surface and reduces oxygen ionization reaction site area, increasing activation polarization

Engineering Contradiction:

Improveprevention of high-resistance layer formationVSAvoidactivation polarization

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent introduces sulfur locally in the second intermediate layer rather than uniformly throughout the cathode structure. This localized sulfur placement ensures SrSO4 formation occurs primarily at the Sr diffusion path (at the perovskite oxide/second intermediate layer interface) rather than covering large areas of the cathode surface, thus preventing high-resistance layer formation while minimizing impact on oxygen ionization reaction sites

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The second intermediate layer containing sulfur acts as an intermediary that facilitates controlled SrSO4 formation. The sulfur in this layer reacts with Sr at the interface to form SrSO4, which then acts as a barrier to further Sr diffusion into the electrolyte, while the layered structure ensures this reaction occurs at specific locations rather than broadly across the cathode surface

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 configuration effectively prevents the formation of high-resistance layers, maintaining power generation performance and reducing the load on the intermediate layer, leading to improved fuel cell and electrolysis cell efficiency.

Implementation Method 1

strontium (Sr) reacts with sulfur (S) and oxygen to form strontium sulfate (SrSO4) in the active layer of the cathode

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 2

a fuel cell for generating electricity by utilizing electrochemical reaction between hydrogen and oxygen

Methodology Applied

Scientific EffectElectrochemical reaction: Fuel Cell

Implementation Method 3

an electrolyte layer containing a solid oxide

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 4

a solid oxide electrolysis cell (hereinafter may be referred to as 'SOEC') for generating hydrogen by utilizing the electrolysis of water

Methodology Applied

Scientific EffectElectrolysis: Electrolysis

Data Source

PatentUS11024856B2Electrochemical reaction single cell having cathode including cerium oxide and strontium sulfate and electrochemical reaction cell stack including the same

Publication Date: 2021.06.01 NITERRA CO LTD

AI summary

An electrochemical reaction unit cell including an electrolyte layer containing a solid oxide; a cathode and an anode which face each other in a first direction with the electrolyte layer intervening therebetween; and an intermediate layer disposed between the electrolyte layer and the cathode and containing a first cerium oxide. In the electrochemical reaction unit cell, the cathode includes an active layer containing a strontium-containing perovskite oxide, a second cerium oxide, sulfur, and strontium sulfate and having ion conductivity and electron conductivity, and a grain of the strontium sulfate covers at least a portion of the surface of a grain of the second cerium oxide.