High-Entropy Oxide Co-Precipitation for Narrow Particle Distribution
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Solution Overview
Problem
Existing methods for synthesizing high-entropy oxides often result in large particles with broad size distributions, which hinder their applications due to limited specific surface area and increased overpotential when used as electrode materials.
Innovation Solution
A method involving the use of at least four metal salts, mixing them in a solvent to form a solution, adding a precipitating agent to obtain a precipitate, and subsequently thermally treating the precipitate to produce a high-entropy oxide, with controlled thermal treatment conditions to achieve a narrow size distribution and homogeneous composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If solid state synthesis method is used to fabricate high-entropy oxides, then the material can be easily prepared, but the particles become large which limits specific surface area and catalytic reaction rates
Solution Approach 1:
The patent replaces the mechanical grinding process of traditional solid-state synthesis with a chemical precipitation process. Metal salts are dissolved in water and precipitated using ammonia or ammonium hydroxide to form hydroxide precursors, which are then calcined to produce oxide particles. This chemical approach enables better control over particle size and surface area compared to mechanical ball milling.
Solution Approach 2:
The patent controls particle size and surface area by adjusting precipitation parameters such as the concentration of metal salt solutions, the addition rate of precipitating agents, temperature, and pH conditions. By optimizing these parameters, the method produces particles with enhanced specific surface area while maintaining the simplicity of the preparation process.
2Manufacturing precision
If co-precipitation method with NaOH or ammonia solution is used, then nanosized particles can be obtained, but severe agglomeration occurs during annealing which broadens size distribution
Solution Approach 1:
The patent introduces a controlled precipitation process using ammonia or ammonium hydroxide as intermediaries to form hydroxide precursors before calcination. This intermediate step allows for homogeneous distribution of multiple metal cations (Mg2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+) in the precipitate, preventing severe agglomeration during subsequent annealing and maintaining composition homogeneity in the final oxide product.
Solution Approach 2:
The patent optimizes precipitation conditions including pH control, temperature, and addition rates to produce uniform hydroxide precursors with narrow size distribution. The controlled precipitation parameters ensure that the subsequent calcining process does not cause severe agglomeration, thereby maintaining both particle size distribution and composition homogeneity.
3Quantity of substance
If nebulised spray pyrolysis is used, then particles with nanometre to micrometre size can be produced, but broad size distribution leads to high overpotential on large particles
Solution Approach 1:
The patent controls particle size and reduces overpotential by optimizing precipitation parameters such as metal salt concentration, precipitating agent addition rate, pH, and temperature. These parameter controls produce particles with narrower size distribution and smaller average size, reducing the formation of large particles that would cause high overpotential during electrochemical reactions.
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 method effectively produces high-entropy oxides with a narrow particle size distribution and uniform composition, enhancing their electrochemical performance and catalytic efficiency by reducing overpotential and improving specific surface area.
Implementation Method 1
mixing the solution obtained in step (b) with a precipitating agent to obtain a precipitate
Implementation Method 2
the thermal treatment step (d) includes a calcining process to provide an oxide intermediate
Implementation Method 3
the thermal treatment step (d) includes an annealing process performed immediately after the calcining process
Data Source
AI summary
Disclosed are high-entropy oxides, and methods of their preparation. The high-entropy oxide is characterised by a sub-micron particle size and rod-like particle shape. The method of its preparation includes a co-precipitation step, preferably using an oxalate compound as a precipitating agent. Also disclosed are an electrode, e.g. an anode, a catalyst and an electrochemical cell comprising the high-entropy oxide.