三相乳液衍生的石墨烯/十八烷相变泡沫，用于耐盐昼夜水分蒸发

摘要：本文，北京化工大学闵芃、于中振教授、李晓锋教授等在《ADVANCED FUNCTIONAL MATERIALS》期刊发表名为“Three-Phase Emulsion Derived Solar-Thermal Reduced Graphene Oxide

1成果简介

本文，北京化工大学闵芃、于中振教授、李晓锋教授等在《ADVANCED FUNCTIONAL MATERIALS》期刊发表名为“Three-Phase Emulsion Derived Solar-Thermal Reduced Graphene Oxide/Octadecane Phase-Change Foam for Salt-Resistant Day-Night Water Evaporation”的论文，研究通过 “空气-油-水 ”三相乳液的界面组装以及氧化石墨烯（GO）的化学还原，制备了一种太阳能-热还原氧化石墨烯/十八烷（RGO/oct）相变泡沫，用于昼夜蒸发和海水淡化。

在两亲性烷基糖苷存在下，GO 片材在水-oct 界面处组装，同时在搅拌下在疏水性 oct 组分内部产生气孔，从而产生 GO/oct/空气微球。在随后的成型过程中，GO 被抗坏血酸化学还原，所得的具有封闭孔隙的 RGO/oct/air 微球构成日热 RGO/oct 相变泡沫。空气孔隙抑制了热量向散装水的传导，而相变辛则阻止了热量向环境的流失，从而增强了 RGO/oct 泡沫的热定位能力。在太阳光照射下，泡沫的蒸发率高达4.29 kg m-2 h-1。有趣的是，在没有太阳光照射的情况下，oct 也能释放潜热，使水在夜间以2.30 kg m-2 h-1 的蒸发率蒸发。微球的重叠成型允许盐浓度梯度的重新排列，在盐水（25 wt.%）中稳定蒸发 10 小时后，泡沫的耐盐性令人满意。

2图文导读

图1、a） RGO/oct 泡沫的制备示意图。b） RGO/oct 泡沫蒸发器的耐盐机制。c） RGO/oct 泡沫蒸发器的相变。

图2、a) Schematic illustration of the microstructure of RGO/oct foam. b,c) SEM images of RGO/oct foam. d) XPS spectra of GO and RGO. C 1s XPS spectra of e) GO and f) RGO. g) Water contact angle images of the RGO/oct foam. Side views of the charge redistribution of h) pristine graphene and RGO containing i) C=O or j) C─O─H, where the yellow areas represent electron accumulation while the blue areas stand for electron depletion.

图3、Schematic showing the heat transmission in a) open-pore RGO foam, b) closed-pore RGO foam, and (c) RGO/oct foam during the water evaporation. d) Comparison of evaporation performance of open-pore RGO foam, closed-pore RGO foam, and RGO/oct foam. Salt excretion performance of e) RGO/oct foam and f) open-pore RGO foam evaporators (salt density is 100 mg cm−2). g) Simulation results of concentration distribution of salt inside the open-pore RGO foam and RGO/oct foam evaporators during the salt excretion processes. h) Mass changes and i) water evaporation rates of the RGO/oct foam in saline solutions with different concentrations.

图4、a) Phase-transition enthalpies of RGO/oct foam with 20, 27, and 33 v/v% of oct. b) Water mass changes and c) evaporation rates of RGO/oct foam with various oct additions under solar light on and off modes. d) Comparison of the evaporation performance of RGO/oct foam (27 v/v%) with previously reported solar evaporators in literature. e) Water mass changes of RGO/oct foam with 27 v/v% oct addition under different solar intensities. f) Surface temperatures of RGO/oct foam during natural cooling after solar radiation with different solar intensities. g) Infrared images of the surfaces of closed-pore RGO foam and RGO/oct foam evaporators under one-sun irradiation, followed by natural cooling without sunlight illumination. Simulations of temperature distribution of h) closed-pore RGO foam evaporator and i) RGO/oct foam evaporator (27 v/v%).

图5、a) Cyclic stability tests of RGO/oct phase-change foam in an aqueous solution with 25 wt.% of NaCl for 5 days (10 h each day) under one-sun irradiation. b) Mass changes of the RGO/oct foam in pure water and real seawater. c) Ion concentrations of seawater and purified water, and d) ion rejection efficiencies of seawater by solar-driven desalination with the RGO/oct phase-change foam. e,f) UV–vis spectra of dye-containing wastewaters before and after the purification. Insets are digital photos of wastewaters before and after the purification. g) Images of wheat seedling growth irrigated by seawater, purified water, and pure water. h) Average lengths of wheat shoot along with cultivation time irrigated by seawater, purified water, and pure water (n = 10).

3小结

通过 o/w/a 三相乳液的界面组装，然后在V 的辅助下对 GO 进行化学还原，制备出了太阳能热 RGO/o oct 相变泡沫。相互连接的 RGO 网络结构完全包裹了 oct微球，抑制了oct的泄漏。亲水性 RGO 网络能将水有效地输送到蒸发表面，并重新排列泡沫内部的盐浓度梯度亚甲基蓝，从而增强其抗盐性。

空心 oct 微球协同利用空气的热局部效应和 oct 的相变潜热，减少向散水和周围环境的散热。因此，RGO/辛烷相变泡沫蒸发器的水蒸发率高达 4.29 kg m-2 h-1，太阳-热转换效率为 87.5%。此外，在黑暗条件下，otc潜热可使 RGO/oct 泡沫蒸发器维持 2.30 kg m-2 h-1 的蒸发率。RGO/oct 相变泡沫具有出色的排盐能力，能在 5 天（每天 10 小时）内保持稳定蒸发 25 wt.% 的氯化钠溶液。为了探索其在农业方面的应用潜力，RGO/oct相变泡沫蒸发器净化后的水可安全用于浇灌小麦播种生长。

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