Ashirov Timur, Yazaydin A Ozgur, Coskun Ali
Department of Chemistry, University of Fribourg, Fribourg, 1700, Switzerland.
Department of Chemical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK.
Adv Mater. 2022 Feb;34(5):e2106785. doi: 10.1002/adma.202106785. Epub 2021 Dec 12.
Porous graphene membranes have emerged as promising alternatives for gas-separation applications due to their atomic thickness enabling ultrahigh permeance, but they suffer from low gas selectivity. Whereas decreasing the pore size below 3 nm is expected to increase the gas selectivity due to molecular sieving, it is rather challenging to generate a large number of uniform small pores on the graphene surface. Here, a pore-narrowing approach via gold deposition onto porous graphene surface is introduced to tune the pore size and thickness of the membrane to achieve a large number of small pores. Through the systematic approach, the ideal combination is determined as pore size below 3 nm, obtained at the thickness of 100 nm, to attain high selectivity and high permeance. The resulting membrane shows a H /CO separation factor of 31.3 at H permeance of 2.23 × 10 GPU (1 GPU = 3.35 × 10 mol s m Pa ), which is the highest value reported to date in the 10 GPU permeance range. This result is explained by comparing the predicted binding energies of gas molecules with the Au surface, -5.3 versus -21 kJ mol for H and CO , respectively, increased surface-gas interactions and molecular-sieving effect with decreasing pore size.
多孔石墨烯膜因其原子厚度可实现超高渗透率，已成为气体分离应用中颇具前景的替代材料，但它们的气体选择性较低。虽然将孔径减小到3纳米以下有望因分子筛效应而提高气体选择性，但在石墨烯表面生成大量均匀的小孔颇具挑战性。在此，引入一种通过在多孔石墨烯表面沉积金来缩小孔径的方法，以调节膜的孔径和厚度，从而获得大量小孔。通过这种系统方法，确定理想的组合是在100纳米厚度下获得孔径低于3纳米的情况，以实现高选择性和高渗透率。所得膜在氢气渗透率为2.23×10 GPU（1 GPU = 3.35×10 mol s m Pa ）时，氢气/一氧化碳分离因子为31.3，这是迄今为止在10 GPU渗透率范围内报道的最高值。通过比较预测的气体分子与金表面的结合能（氢气为 -5.3 kJ/mol，一氧化碳为 -21 kJ/mol）、随着孔径减小而增加的表面 - 气体相互作用和分子筛效应来解释这一结果。
