Martell Sarah A, Werner-Zwanziger Ulrike, Dasog Mita
Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, NS, Canada.
Faraday Discuss. 2020 Jun 19;222(0):176-189. doi: 10.1039/c9fd00098d.
H2 has been identified as one of the potential energy vectors that can provide a sustainable energy supply when produced through solar-driven water-splitting reaction. Si is the second most abundant element in the Earth's crust and can absorb a significant fraction of the solar spectrum while presenting little toxicity risk, making it an attractive material for photocatalytic H2 production. Hydrogen-terminated mesoporous Si (mp-Si) nanoparticles can be utilized to effectively drive the hydrogen evolution reaction using UV-to-visible light. In this work, the response of the photocatalytic activity of mp-Si nanoparticles to a series of HF acid treatments was investigated. A two-step magnesiothermic reduction method was used to prepare crystalline mp-Si nanoparticles with a specific surface area of 573 m2 g-1. The HF etching process was optimized as a function of the amount of acid added and the reaction time. The reaction time did not influence the H2 evolution rate substantially. However, the amount of HF used did have a significant effect on the photocatalytic activity. In the presence of ≥1.0 mL HF acid per 0.010 g of Si, morphological damage was observed using electron microscopy. N2 adsorption measurements indicated that the pore size and surface area were also altered. Solution-phase 19F{1H} NMR studies indicated the formation of SiF5- and SiF62- when larger volumes of HF were used. Both factors, morphological damage and the presence of byproducts in the pores, likely result in a lowering of the photocatalytic H2 evolution rate. Under the optimized HF treatment conditions (0.5 mL of HF per 0.010 g of Si), a H2 evolution rate of 1398 ± 30 μmol g-1 h-1 was observed.
氢气已被确定为潜在的能量载体之一，当通过太阳能驱动的水分解反应产生时，它可以提供可持续的能源供应。硅是地壳中含量第二丰富的元素，能吸收很大一部分太阳光谱，同时毒性风险极小，这使其成为光催化制氢的理想材料。氢封端的介孔硅（mp-Si）纳米颗粒可用于利用紫外光到可见光有效驱动析氢反应。在这项工作中，研究了mp-Si纳米颗粒的光催化活性对一系列氢氟酸处理的响应。采用两步镁热还原法制备了比表面积为573 m2 g-1的结晶mp-Si纳米颗粒。氢氟酸蚀刻工艺根据添加的酸量和反应时间进行了优化。反应时间对析氢速率影响不大。然而，所用氢氟酸的量对光催化活性有显著影响。每0.010 g硅中存在≥1.0 mL氢氟酸时，通过电子显微镜观察到形态损伤。氮气吸附测量表明孔径和表面积也发生了变化。溶液相19F{1H}核磁共振研究表明，当使用大量氢氟酸时会形成SiF5-和SiF62-。形态损伤和孔中副产物的存在这两个因素都可能导致光催化析氢速率降低。在优化的氢氟酸处理条件下（每0.010 g硅0.5 mL氢氟酸），观察到析氢速率为1398±30 μmol g-1 h-1。
