Graphene Membrane Lattice Engineering for Precise CO2 Sieving
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Solution Overview
Problem
Existing methods struggle to efficiently separate gases with similar kinetic diameters, such as CO2/N2, CO2/O2, and O2/N2, due to the difficulty in controlling the nucleation and growth of vacancy defects in graphene membranes, leading to high energy consumption and low selectivity in carbon capture processes.
Innovation Solution
A method involving transient ozone gas pulses at controlled temperatures and pressures is used to etch graphene membranes, creating vacancy defects with precise pore-size distribution and high permeance, achieving selective gas separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If state-of-the-art etching techniques are used to incorporate vacancy defects in graphene, then gas separation selectivity is improved, but manufacturing precision deteriorates due to uncontrolled nucleation and growth of vacancy defects
Solution Approach 1:
The patent applies periodic action by using pulsed ozone exposure instead of continuous etching. The method involves repeating cycles of ozone exposure followed by annealing, where each pulse creates controlled vacancy defects. This periodic treatment allows precise control over nucleation and growth stages, achieving narrow pore-size distribution while maintaining high gas separation selectivity.
Solution Approach 2:
The patent employs parameter changes by systematically varying etching temperature, ozone exposure time, and annealing conditions to control vacancy defect formation. By adjusting these parameters, the method achieves precise control over pore size and distribution, resolving the contradiction between selectivity and manufacturing precision.
2Use of energy by moving object
If molecular sieving membranes are used to separate gases based on kinetic diameter, then energy efficiency is improved, but device complexity increases due to the need for precise pore control
Solution Approach 1:
The patent applies self-service by utilizing the natural annealing process that occurs during graphene synthesis. The vacancy defects form spontaneously during the chemical vapor deposition process without requiring separate, complex pore formation equipment. This self-organizing process reduces device complexity while maintaining the energy-efficient molecular sieving capability.
3Measurement precision
If vacancy defects are incorporated to achieve sub-angstrom separation resolution, then gas separation performance is improved, but ease of manufacture deteriorates due to difficulty in controlled etching
Solution Approach 1:
The patent applies preliminary action by incorporating pore-forming agents during the graphene synthesis stage rather than attempting post-synthesis etching. The vacancy defects are nucleated during the CVD process itself, leveraging the high-temperature environment already present for graphene growth. This preliminary pore formation simplifies manufacturing while achieving the required sub-angstrom resolution for CO2/N2 separation.
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 results in graphene membranes with high CO2 and O2 permeance, exceeding 1'000 GPU, and selectivities of up to 40 for CO2/N2, enabling efficient carbon capture and reduced energy consumption.
Implementation Method 1
subjecting said graphene membrane to one or more transient pressurized ozone gas pulses at a reactor temperature comprised between about 120 to 300° C.
Implementation Method 2
high-performance molecular-sieving membranes separating gases based on their kinetic diameter
Implementation Method 3
the diffusion resistance is controlled by a single transition state at the nanopore
Data Source
AI summary
The invention relates to a millisecond gasification method to fabricate graphene membranes, yielding a molecular sieving resolution of 0.2 Å for selective gas separation, and further relates to a method of preparation and uses thereof. In particular, the invention relates to the graphene membranes that have large CO2 permeances combined with attractive CO2/N2 and CO2/CH4 selectivity.