Diaphragm-Electrode Assembly for High Purity Hydrogen
Solution Overview
Problem
Existing water electrolysis cells face challenges in achieving high purity hydrogen production at high current densities while maintaining low cell voltage, with membrane cells experiencing ohmic drop issues and diaphragm cells producing low purity hydrogen due to oxygen diffusion.
Innovation Solution
An assembly of a gas-evolving electrode with a porous body containing an electrocatalyst in a conductive matrix and a porous separator diaphragm with inorganic hydrophilic particulates is used, where the gas-evolving electrode has a very fine porosity and a catalyst gradient, enhancing hydrogen purity and reducing cell voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion-exchange membranes are used in water electrolysis cells, then high purity hydrogen production is achieved, but ohmic drop increases significantly at high current densities
Solution Approach 1:
The patent employs composite materials by combining a porous diaphragm substrate with dispersed inorganic hydrophilic particulates (such as metal oxides or hydroxides) to create a diaphragm-electrode assembly that exhibits both low ohmic resistance and high hydrogen purity. The composite structure leverages the conductive properties of the inorganic particles while maintaining the porous architecture for efficient ion transport.
Solution Approach 2:
The invention utilizes porous materials as the foundational structure of the diaphragm, which allows for high electrolyte saturation and efficient ion conduction. The porous network provides continuous pathways for ion transport while the dispersed inorganic hydrophilic particulates enhance the hydrophilicity and ionic conductivity of the overall structure, enabling low ohmic drop operation at high current densities.
2Loss of energy
If porous diaphragms are used in water electrolysis cells, then low ohmic drop is achieved at high current densities, but hydrogen purity decreases due to oxygen diffusion
Solution Approach 1:
The patent applies local quality by creating regions with different properties within the diaphragm structure. The dispersed inorganic hydrophilic particulates are locally distributed throughout the porous network, creating zones of enhanced hydrophilicity and ion conduction that preferentially guide ion transport while limiting gas diffusion pathways. This local modification of properties allows the diaphragm to simultaneously achieve low ohmic drop and high hydrogen purity.
Solution Approach 2:
The inorganic hydrophilic particulates act as intermediaries within the diaphragm structure, mediating between the porous network and the electrolyte. These particles enhance the hydrophilic character of the diaphragm, promoting electrolyte saturation and ion conduction while the overall porous structure maintains gas-tight separation. The intermediary particles facilitate ion transport while the structured porous matrix prevents oxygen diffusion, resolving the contradiction between low ohmic drop and high purity.
3Manufacturing precision
If inorganic hydrophilic particulates are dispersed in a porous network, then hydrogen purity exceeds 99.8% at high current densities, but device complexity increases
Solution Approach 1:
The patent merges the diaphragm function and electrode function into a single integrated diaphragm-electrode assembly. The inorganic hydrophilic particulates are directly dispersed within the porous diaphragm network, combining the separator and electrode components into one unit. This merging eliminates the need for separate electrodes and diaphragms, reducing assembly complexity while achieving high hydrogen purity through the optimized porous structure with dispersed hydrophilic particles.
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 solution allows for the production of hydrogen with purities exceeding 99.8% at voltages typical of diaphragm cells, matching the purity of membrane cells, while maintaining stability at high current densities without scalability issues.
Implementation Method 1
a gas-evolving electrode made of a porous body having a pore size below 50 nm containing an electrocatalyst dispersed in a conductive matrix
Implementation Method 2
one major surface of a generally planar separator diaphragm comprising inorganic hydrophilic particulates dispersed in a porous network
Implementation Method 3
the hydrogen purity is severely penalised by the oxygen travelling across the diaphragm. This inconvenience is caused by the diffusion rate of oxygen in the liquid phase filling the porosity
Implementation Method 4
The electrolyte which fills the internal porosity of the diaphragm allows to operate with much lower ohmic drops even at very high current densities
Data Source
AI summary
The invention relates to an assembly of a porous gas-evolving electrode and a porous separator diaphragm, suitable for use in a water electrolyser operating with an alkaline electrolyte. A water electrolyser having the gas-evolving electrode component of the assembly arranged as the cathode allows manufacturing hydrogen with a purity exceeding 99.8%.