Ultrafast Diameter-Dependent Water Evaporation from Nanopores
Ultrafast Diameter-Dependent Water Evaporation from Nanopores
复制标题
DOI：
10.1021/acsnano.8b09258
复制
发表时间：
2019-03-01
期刊：
影响因子：
17.1
通讯作者：
Duan, Chuanhua
中科院分区：
文献类型：
--
作者：
Li, Yinxiao;Chen, Haowen;Duan, Chuanhua
纳米孔的蒸发在各种需要高效传热和传质的自然和工业过程中发挥着重要作用。基于纳米孔蒸发的工艺的最终性能取决于液-气界面处的蒸发动力学，其尚未被实验研究到单个纳米孔水平。在这里，我们报告明确的测量动力学有限的强烈蒸发从个别亲水性纳米孔与亲水性和疏水性的顶部外表面在22摄氏度使用纳米通道连接的纳米孔设备。我们的研究结果表明，具有亲水性外表面的纳米孔的蒸发通量显示出强烈的直径依赖性，其指数接近-1.5，在孔径为27 nm时达到经典Hertz-Knudsen关系提供的最大理论预测的11倍。结果表明，具有疏水外表面的纳米孔的蒸发通量表现出不同的直径依赖性，其指数为-0.66，在孔径为28 nm时达到最大理论预测值的66%。我们发现具有亲水外表面的纳米孔的超快直径依赖性蒸发主要源于纳米孔外的水薄膜的蒸发。与此相反，从具有疏水性外表面的纳米孔的直径依赖性蒸发由纳米孔内的蒸发动力学控制，这表明蒸发系数在不同的纳米级约束中变化，可能是由于表面电荷诱导的水合氢离子浓度变化。这项研究增强了我们对纳米尺度下蒸发的理解，并展示了纳米孔蒸发的巨大潜力。
Evaporation from nanopores plays an important role in various natural and industrial processes that require efficient heat and mass transfer. The ultimate performance of nanopore-evaporation-based processes is dictated by evaporation kinetics at the liquid-vapor interface, which has yet to be experimentally studied down to the single nanopore level. Here we report unambiguous measurements of kinetically limited intense evaporation from individual hydrophilic nanopores with both hydrophilic and hydrophobic top outer surfaces at 22 degrees C using nanochannel-connected nanopore devices. Our results show that the evaporation fluxes of nanopores with hydrophilic outer surfaces show a strong diameter dependence with an exponent of nearly -1.5, reaching up to 11-fold of the maximum theoretical predication provided by the classical Hertz-Knudsen relation at a pore diameter of 27 nm. Differently, the evaporation fluxes of nanopores with hydrophobic outer surfaces show a different diameter dependence with an exponent of -0.66, achieving 66% of the maximum theoretical predication at a pore diameter of 28 nm. We discover that the ultrafast diameter-dependent evaporation from nanopores with hydrophilic outer surfaces mainly stems from evaporating water thin films outside of the nanopores. In contrast, the diameter-dependent evaporation from nanopores with hydrophobic outer surfaces is governed by evaporation kinetics inside the nanopores, which indicates that the evaporation coefficient varies in different nanoscale confinements, possibly due to surface-charge-induced concentration changes of hydronium ions. This study enhances our understanding of evaporation at the nanoscale and demonstrates great potential of evaporation from nanopores.