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Volume 222, 2020

The influence of hydrofluoric acid etching processes on the photocatalytic hydrogen evolution reaction using mesoporous silicon nanoparticles

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Abstract

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.

Graphical abstract: The influence of hydrofluoric acid etching processes on the photocatalytic hydrogen evolution reaction using mesoporous silicon nanoparticles

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Supplementary files

Article information


Submitted
30 Sep 2019
Accepted
16 Oct 2019
First published
16 Oct 2019

Faraday Discuss., 2020,222, 176-189
Article type
Paper

The influence of hydrofluoric acid etching processes on the photocatalytic hydrogen evolution reaction using mesoporous silicon nanoparticles

S. A. Martell, U. Werner-Zwanziger and M. Dasog, Faraday Discuss., 2020, 222, 176 DOI: 10.1039/C9FD00098D

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