Silver-Zirconia Porous Clusters for Stable Metal-Air Electrodes
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Solution Overview
Problem
Silver catalysts used in metal-air cells and batteries face degradation due to the formation of silver oxides in alkaline electrolytes, leading to dissolution and reduced electrode performance, as they are prone to oxidation and decomposition, which affects the stability and efficiency of oxygen reduction reactions.
Innovation Solution
A tri-functional gas-diffusion electrode comprising porous clusters of silver particles with crystalline ZrO2 particles on their surface, which functions as a catalyst for oxygen reduction, provides additional energy through silver oxide reduction, and acts as a counter/auxiliary electrode for hydroxide ion oxidation, enhancing stability and performance in both discharge and charge modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver catalyst is used in metal-air cells with alkaline electrolyte, then oxygen reduction catalysis is achieved, but silver oxide formation causes catalyst dissolution and degradation
Solution Approach 1:
Zirconium oxide particles are introduced as an intermediary substance that interacts with silver particles to form a composite catalyst. The ZrO2 acts as a mediator that prevents direct contact between silver and the alkaline electrolyte, thereby reducing silver oxide formation and dissolution while maintaining catalytic activity for oxygen reduction reactions.
Solution Approach 2:
The invention creates a composite catalyst material consisting of silver particles combined with zirconium oxide particles. This composite structure leverages the high catalytic activity of silver while the zirconium oxide component provides stability and resistance to alkaline corrosion, solving the contradiction between catalytic performance and chemical stability.
2Use of energy by moving object
If silver catalyst undergoes deep oxidation and reduction cycles during charging and discharging, then additional energy is provided, but catalyst morphology and activity degrade
Solution Approach 1:
The zirconium oxide particles are pre-introduced to the silver catalyst before the electrode undergoes charging and discharging cycles. This creates a protective structure in advance that cushions the silver particles against the damaging effects of repeated oxidation and reduction, preventing morphology degradation and maintaining catalytic activity throughout the battery's operational life.
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 electrode maintains morphology and catalytic activity after deep oxidation and reduction cycles, providing improved stability and energy efficiency, with additional energy contributed by silver oxide reduction processes, extending the lifespan and performance of metal-air cells and batteries.
Implementation Method 1
the oxidizing reactant (oxygen) which undergoes reduction during discharge is supplied from outside the cell. This reaction of oxygen reduction occurs in the presence of water and gives hydroxide ions (OH−). The oxygen is reduced on the surface of the cathode during discharge. The cathode comprises a material that catalyzes the above-mentioned oxygen reduction.
Implementation Method 2
At an anodic oxidation of silver in alkaline solution, the first phase transition at a potential of +0.24V is Ag→Ag2O. The next phase transition is Ag2O→AgO at a potential of about +0.5V.
Implementation Method 3
If a silver-catalyzed cathode works as a bi-functional electrode, the potentials in the charge mode of operation could reach +0.4-0.5V and even higher, until the process of oxygen evolution occurs. This means that substantially all the problems of silver catalyst dissolution result from the formation of different types of silver oxides at OCV and anodic polarization, and their subsequent decomposition and precipitation.
Data Source
AI summary
This invention provides a rechargeable cell comprising an electrode including: a plurality of porous clusters of silver particles, wherein each cluster includes: (a) a plurality of silver particles, and (b) crystalline particles of zirconium oxide (ZrO2), wherein at least a portion of the crystalline particles of ZrO2 is located in pores formed by a surface of the plurality of silver particles. Electrodes of the present invention catalyze the reduction of oxygen in alkaline solution. When the cell is charged, the silver in the electrodes can be oxidized to Ag2O and further to AgO. Upon discharge, the reduction of the oxidized silver results in additional available energy. This invention provides electrodes for use in rechargeable cells or batteries and methods of making thereof.