Graphene Membrane Lattice Engineering for Precise Gas 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 selectivity, achieving CO2 and O2 permeances exceeding 1'000 GPU with selectivities of 10 to 50 for CO2/N2 and O2/N2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If state-of-the-art etching techniques are used to create vacancy defects in graphene, then gas separation capability is improved, but manufacturing precision deteriorates due to uncontrolled nucleation and growth of vacancy defects
Solution Approach 1:
The patent employs periodic pulsed ozone treatment instead of continuous etching. The process uses multiple short ozone pulses (e.g., 10-100 ms duration) separated by intervals, allowing controlled nucleation and growth of vacancy defects. This periodic action enables precise control over pore-size distribution while maintaining gas separation capability, resolving the contradiction between reliability and manufacturing precision.
Solution Approach 2:
The patent applies preliminary thermal annealing treatment to the graphene membrane before ozone etching. This preliminary action prepares the graphene lattice by removing adsorbed species and creating a uniform initial state, which enables subsequent controlled vacancy defect formation with narrow pore-size distribution during the ozone treatment process.
2Productivity
If high CO2 permeance is achieved through increased pore density, then separation efficiency is improved, but selectivity deteriorates due to broader pore-size distribution
Solution Approach 1:
The patent systematically changes multiple parameters including ozone concentration, pulse duration, number of pulses, and thermal annealing conditions to achieve the optimal balance between CO2 permeance and selectivity. By controlling the ozone dose and pulse characteristics, the process achieves high pore density with narrow size distribution, simultaneously improving productivity and reliability.
Solution Approach 2:
The patent implements a feedback-controlled ozone delivery system that monitors the etching process in real-time. Based on feedback from process monitoring and post-treatment characterization, the ozone pulse parameters are adjusted to maintain narrow pore-size distribution while achieving target CO2 permeance levels, thus preserving selectivity during productivity enhancement.
3Ease of manufacture
If conventional etching methods are used, then processing simplicity is maintained, but energy consumption increases due to prolonged treatment times and uncontrolled defect formation
Solution Approach 1:
The patent uses short-duration ozone pulses (10-100 ms) to rapidly create the desired vacancy defects, skipping through the prolonged treatment times required by conventional continuous etching methods. This rushed approach through the etching process reduces energy consumption while achieving the same or better defect formation efficiency, particularly when combined with thermal annealing that accelerates defect relaxation.
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 narrow pore-size distribution, high permeance, and selectivity, reducing energy consumption and capital costs in carbon capture processes, suitable for industrial-scale gas separation.
Implementation Method 1
subjecting said graphene membrane to one or more transient pressurized ozone gas pulses
Implementation Method 2
molecular separation, a key component of industrial processes and at the heart of environmental issues like carbon capture
Implementation Method 3
the diffusion resistance is controlled by a single transition state at the nanopore
Implementation Method 4
CO2 permeance exceeding 1'000 GPU with selectivities of 10 to 50 for CO2/N2 and O2/N2
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.