CO2 Electrolysis Reactor with Gas Diffusion Cathode
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Solution Overview
Problem
Current methods for reducing carbon dioxide to carbonate and formate have low product concentration and Faradaic efficiency, requiring separate separation and concentration processes due to non-spontaneous gas-phase reactions and high energy consumption.
Innovation Solution
An electrolysis reactor system with an anode, ion-exchange membrane, and cathode, using a Group I metal salt electrolytic solution and gas diffusion layer to facilitate the reduction of CO2 to carbonate and formate, with voltage application and pH-controlled replenishment of electrolytic solutions to enhance reaction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If liquid-phase reaction of carbon dioxide is used, then Faradaic efficiency is improved (higher than 80%), but product concentration becomes very low (several ppm) requiring separate separation and concentration processes
Solution Approach 1:
The invention changes the physical state parameter of CO2 from liquid-phase to gas-phase, and changes the reaction environment from bulk liquid to gas-liquid interface. This parameter change allows achieving high Faradaic efficiency (>80%) while obtaining high product concentration (several tens of mmol/L to several hundreds of mmol/L) by conducting the reduction reaction at the gas-liquid interface on the cathode surface.
Solution Approach 2:
The invention utilizes phase transition by supplying CO2 gas to the cathode where it contacts the liquid electrolyte film. The CO2 transitions from gas phase to dissolved state at the gas-liquid interface, enabling both high Faradaic efficiency and high product concentration by maintaining the reaction at the interface rather than in bulk liquid.
2Quantity of substance
If gas-phase reduction reaction of carbon dioxide is used, then product concentration is improved (several mmol/L to several tens of mmol/L), but Faradaic efficiency becomes very low (highest reported 10%)
Solution Approach 1:
The invention employs a gas-liquid system where CO2 gas is supplied to the cathode and contacts a liquid electrolyte film. This pneumatic-hydraulic configuration allows the gas-phase CO2 to react at the gas-liquid interface, achieving both high product concentration (several tens of mmol/L to several hundreds of mmol/L) and high Faradaic efficiency (>80%).
Solution Approach 2:
The invention utilizes phase transition by supplying CO2 gas to the cathode where it contacts the liquid electrolyte film. The CO2 transitions from gas phase to dissolved state at the gas-liquid interface, enabling both high Faradaic efficiency (>80%) and high product concentration (several tens of mmol/L to several hundreds of mmol/L) by maintaining the reaction at the interface rather than in bulk liquid.
3Quantity of substance
If conventional CO2 reduction methods are used, then separation and concentration processes are required, but this increases processing cost and device complexity
Solution Approach 1:
The invention extracts only the essential function of CO2 reduction to occur at the gas-liquid interface on the cathode, eliminating the need for separate separation and concentration processes. By designing the cathode to directly produce high-concentration carbonate and formate (several tens of mmol/L to several hundreds of mmol/L), the system removes the complexity of downstream processing equipment.
Solution Approach 2:
The cathode structure and reaction conditions are designed to self-generate high product concentration during the reduction process. The gas-liquid interface reaction inherently produces carbonate and formate at concentrations of several tens of mmol/L to several hundreds of mmol/L, making the system self-sufficient and eliminating the need for external separation and concentration equipment.
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 system achieves high concentration and Faradaic efficiency of carbonate and formate production, reducing separation and concentration costs by promoting spontaneous reduction reactions in a liquid-like environment with minimal water usage.
Implementation Method 1
an ion-exchange membrane through which metal cations derived from the Group I metal salt and water flow from an anode to a cathode
Implementation Method 2
water undergoes electrolysis to generate hydrogen ions, oxygen, and electrons
Implementation Method 3
carbon dioxide reacts with the electrons and hydrogen cations generated at the anode to cause a reduction reaction and is converted to a different material
Data Source
AI summary
The present invention relates to an apparatus and method of preparing carbonate and/or formate from carbon dioxide. The apparatus of preparing carbonate and/or formate from carbon dioxide (CO2), comprising: an electrolysis reactor comprising (i) an anode which contains an aqueous solution of a Group I metal salt as an electrolytic solution, (ii) an ion-exchange membrane through which metal cations derived from the Group I metal salt and water flow from an anode to a cathode, (iii) a cathode, and (iv) a gas diffusion layer which supplies a carbon dioxide-containing gas to the cathode; a power supply unit of applying a voltage between the anode and the cathode; a first gas-liquid separator of recovering the electrolytic solution from the products formed in the anode; a second gas-liquid separator of recovering carbonate and/or formate from the products formed in the cathode; a pH meter of measuring the pH of the electrolytic solution recovered from the first gas-liquid separator; a first reactant supply unit of supplying (a) the electrolytic solution recovered from the first gas-liquid separator and (b) the aqueous solution of the Group I metal salt with which the recovered electrolytic solution is replenished according to the pH of the electrolytic solution, to the anode; and a second reactant supply unit of supplying carbon dioxide or a mixer comprising carbon dioxide and water vapor to the cathode; wherein, when a voltage is applied between the anode and the cathode, in the anode, water undergoes electrolysis to generate hydrogen ions, oxygen, and electrons, and metal cations in the Group I metal salt are substituted with the hydrogen ions, while the generated metal cations move to the cathode through the ion-exchange membrane and the electrons move to the cathode through an external electric line; and in the cathode, carbon dioxide, water, metal cations, and electrons are reacted and produce carbonate and/or formate.