Montjoy Douglas G, Hou Harrison, Bahng Joong Hwan, Eskafi Aydin, Jiang Ruiyu, Kotov Nicholas A
Department of Electrical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
Jiangsu Collaborative Innovation Center for Ecological Building Material and Environmental Protection Equipment, Yancheng Institute of Technology, Yancheng 224051, China.
ACS Nano. 2021 Mar 23;15(3):4226-4234. doi: 10.1021/acsnano.0c05992. Epub 2021 Feb 19.
High ionic strength environments can profoundly influence catalytic reactions involving charged species. However, control of selectivity and yield of heterogeneous catalytic reactions involving nano- and microscale colloids remains hypothetical because high ionic strength leads to aggregation of particle dispersions. Here we show that microscale hedgehog particles (HPs) with semiconductor nanoscale spikes display enhanced stability in solutions of monovalent/divalent salts in both aqueous and hydrophobic media. HPs enable tuning of photocatalytic reactions toward high-value products by adding concentrated inert salts to amplify local electrical fields in agreement with Derjaguin, Landau, Verwey, and Overbeek theory. After optimization of HP geometry for a model photocatalytic reaction, we show that high salt conditions increase the yield of HP-facilitated photooxidation of 2-phenoxy-1-phenylethanol to benzaldehyde and 2-phenoxyacetophenone by 6 and 35 times, respectively. Depending on salinity, electrical fields at the HP-media interface increase from 1.7 × 10 V/m to 8.5 × 10 V/m, with high fields favoring products generated intermediate cation radicals rather than neutral species. Electron transfer rates were modulated by varying the ionic strength, which affords a convenient and hardly used reaction pathway for engineering a multitude of redox reactions including those involved in the environmental remediation of briny and salty water.
高离子强度环境会深刻影响涉及带电物种的催化反应。然而，对于涉及纳米和微米级胶体的多相催化反应，其选择性和产率的控制仍只是一种假设，因为高离子强度会导致颗粒分散体聚集。在此，我们表明具有半导体纳米级尖刺的微米级刺猬颗粒（HPs）在水性和疏水性介质中的单价/二价盐溶液中表现出增强的稳定性。根据德亚金、朗道、韦弗伊和奥弗贝克理论，通过添加浓惰性盐以增强局部电场，HPs能够将光催化反应调节至生成高价值产物。在针对模型光催化反应优化HP几何结构后，我们发现高盐条件下HP促进的2-苯氧基-1-苯基乙醇光氧化为苯甲醛和2-苯氧基苯乙酮的产率分别提高了6倍和35倍。根据盐度不同，HP-介质界面处的电场从1.7×10 V/m增加到8.5×10 V/m，高电场有利于通过中间阳离子自由基而非中性物种生成产物。通过改变离子强度来调节电子转移速率，这为设计众多氧化还原反应提供了一条便捷且鲜少使用的反应途径，包括那些涉及盐水和咸水的环境修复反应。
