Among potential semiconductors, silicon nanowire (SiNWs) is one of the promising materials that can be used in the photocatalytic hydrogen generation reaction. However, the factors affecting its photocatalytic activity have yet to be widely discussed. The proposed paper provides an in-depth fundamental understanding of light-driven hydrogen generation using nanostructured silicon as a highly promising surface for efficient hydrogen generation [1, 2]. Our results are based on vibrational, UV–vis, and X-ray spectroscopy studies. Our investigations convincingly show that two possibilities of hydrogen generation, i.e., oxidation of SiNWs and photostimulation, are jointly responsible for significant hydrogen generation. In addition, the precise localization of silver nanoparticles as a co-catalyst on the sidewall of SiNWs can enhance the hydrogen generation rate. The SiNWs array with increased amounts of active surface sites shows better charge collection efficiency and longer electron lifetime on the surface. In contrast, the charge recombination at the SiNW/electrolyte interface is more encouraged due to the increase of surface trap states. Furthermore, we demonstrate a new possible photocatalytic application of SiNWs array using artificial seawater with different concentrations of sodium chloride, which can take advantage of the abundance of seawater. Indeed, chlorine ions can serve as a hole scavenger and effectively capture the photogenerated holes, improving the charge separation efficiency. On the other hand, the high concentration of chlorine ions in the solution can concomitantly induce the back-reduction reaction with the photogenerated electrons and decompose the silver nanoparticles, which act as a co-catalyst, encouraging charge separation on the SiNWs surface. Thus, the visible-light-driven hydrogen production on the SiNWs array with the optimized NaCl concentration of 0.7% (similar to the Baltic Sea salinity) yielded significantly enhanced performance compared to the deionized water.

[1] Tingsen Ming, Sergey Turishchev, Alexander Schleusener, Elena Parinova, Dmitry Koyuda, Olga Chuvenkova, Martin Schulz, Benjamin Dietzek, Vladimir Sivakov, Silicon Suboxides as Driving Force for Efficient Light‐Enhanced Hydrogen Generation on Silicon Nanowires, Small 2021, 17(8), 2007650.
[2] Tingsen Ming, Benjamin Dietzek-Ivanšić, Xiaoju Lu, Xiaohua Zuo, Vladimir Sivakov, Silicon Nanowires Decorated with Silver Nanoparticles for Photoassisted Hydrogen Generation, ACS Applied Energy Materials 2022, 5, 6, 7466–7472.