Molecular sieving is of great importance to proton exchange in fuel cells, water desalination, and gas separation. Two-dimensional crystals emerge as superior materials showing desirable molecular permeability and selectivity. Here we demonstrate that a graphdiyne membrane, an experimentally fabricated member in the graphyne family, shows superior proton conductivity and perfect selectivity thanks to its intrinsic nanomesh structure. The trans-membrane hydrogen bonds across graphdiyne serve as ideal channels for proton transport in Grotthuss mechanism. The free energy barrier for proton transfer across graphdiyne is ~2.4 kJ mol−1, nearly identical to that in bulk water (2.1 kJ mol−1), enabling “transparent” proton transport at room temperature. This results in a proton conductivity of 0.6 S cm−1 for graphdiyne, four orders of magnitude greater than graphene. Considering its ultimate pore size of 0.55 nm, graphdiyne membrane blocks soluble fuel molecules and exhibits superior proton selectivity. These advantages endow graphdiyne a great potential as proton exchange material.
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机译：分子筛对于燃料电池中的质子交换，水脱盐和气体分离非常重要。二维晶体作为优越的材料出现，表现出理想的分子渗透性和选择性。在这里，我们证明了石墨二炔膜是石墨烯家族中的一个实验性制造成员，由于其固有的纳米网状结构，它显示出了卓越的质子传导性和完美的选择性。跨石墨二炔的跨膜氢键是Grotthuss机理中质子传输的理想通道。质子跨石墨二炔转移的自由能垒为〜2.4 kJ mol -1 ，与散装水中的自由能垒几乎相同（2.1 kJ mol -1 ），实现了“透明”质子在室温下运输。这导致石墨二炔的质子电导率为0.6 S cm -1 ，比石墨烯大四个数量级。考虑到其最终孔径为0.55 nm，石墨二炔膜可阻挡可溶性燃料分子并表现出优异的质子选择性。这些优点赋予了石墨二炔作为质子交换材料的巨大潜力。
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