Ruike Li,Meicheng Li,Yingfeng Li,Pengfei Fu,Younan Luo,Rui Huang,Dandan Song,Joseph Michel Mbengue
Metal-assisted chemical etching is a very popular method of fabricating silicon nanostructures. For the dissolution and recrystallization of Ag and the inertia of Au, we present a co-catalytic mechanism of silicon etching using non-overlapping Au and Ag nanofilms. Meanwhile, two kinds of novel nanostructures are obtained by changing the relative positions of the two nanofilms. The results show that regardless of whether the Ag or Au nanofilm is the upper layer, the Ag nanofilm will first react to etch the silicon substrate into silicon nanowires (Si NWs). Afterwards, the Au nanofilm will re-etch the Si NWs into thick pillars (Ag upper) or ultrathin porous Si NWs (Au upper). It should be noted that the vertical etching rates of the two layers are not observably different, in contrast to when the Au and Ag nanofilms are used separately, in which the vertical etching rate of the Ag nanofilm is much higher than that of the Au nanofilm. This occurs because the subsequent re-etching process by the Au nanofilm is conducted at multiple surfaces because Au can generate excessive holes during the decomposition of hydrogen peroxide. Furthermore, this study presents a feasible method for the fabrication of individual, thick (∼200 nm) silicon pillars and ultrathin (∼25 nm) porous Si NWs. These insights are significant for the syntheses of many nanostructures.
Tao Zhou,Xianghua Zhao,Jiangfan Liao,Qingrun Xie,Mingli Xu,Tai Li,Guoqiang Lv,Xiufeng Li,Wenhui Ma
The rapid growth of the photovoltaic (PV) industry has resulted in massive generation of silicon wafer debris, posing both environmental and resource-utilization challenges. Achieving sustainable and high-value use of this silicon waste for photoelectrochemical hydrogen evolution reaction (PEC-HER) remains highly desirable yet technically challenging. Silicon wafer debris was etched via a metal-assisted chemical etching (MACE) process to obtain silicon nanowires (Si NWs). The morphology of MoS 2 was further tailored through a polyvinylpyrrolidone (PVP)-assisted hydrothermal method, followed by the formation of MoS 2 /Si NWs heterostructures. This sustainable strategy integrates resource recycling with morphology control and heterostructure engineering, enabling uniform MoS 2 coverage, optimized interfacial coupling, and accelerated charge transfer, thereby enhancing the PEC-HER efficiency. The Nano-MoS 2 /Si NWs exhibited a Tafel slope of 167 mV⋅dec −1 , significantly lower than that of pristine Si NWs (524 mV⋅dec −1 ), indicating accelerated hydrogen evolution kinetics. The hydrogen production rate reached 404.77 μmol cm −2 , corresponding to a 196.3% enhancement compared with Si NWs (136.62 μmol cm −2 ). Finite element analysis further revealed markedly enhanced and uniformly distributed current density and surface H + concentration for MoS 2 /Si NWs, attributed to their abundant exposed active edge sites and improved interfacial charge transfer, which collectively contribute to the enhanced PEC-HER performance. This work advances a sustainable upcycling route that converts PV silicon wafer debris into functional photocathodes and offers a general approach to morphology control and heterostructure engineering for efficient, eco-friendly solar-to-hydrogen conversion.
Micro-direct methanol fuel cells (μ-DMFCs) show the promising feasibility in the various portable practical scenes, although the anode still remains the high cost and low anti-toxic ability of noble metal (viz. Pt). Using photo-responsive anodes to boost the performance of fuel cell activity and stability with the aid of light illumination has been as the new strategy and herein we construct core–shell structure of Si nanowires (NWs)@ZnO anode to investigate the performance of μ-DMFCs under light illumination. The short circuit current and open circuit voltage of Si NWs@ZnO heterojunction are 100.5 μA cm −2 and 0.7 V, respectively, which are 3.5 and 1.3 times higher than Si NWs under light illumination. The Si NWs@ZnO photoanode also kept 97.3 % of current density for the second reused. A record-high discharge voltage of 0.7 V and more than 12 h of discharge time were achieved in photo-assisted μ-DMFCs. Carefully designed core–shell structure and the matched energy levels between Si NWs and ZnO contribute to the significant improved performances, where they can attenuate the light reflexes of the polished silicon, strengthen photos absorption and boost the charge transfer kinetics. This study opens an appealing research direction based on photo-assisted non-noble semiconductor anode toward the high-performance μ-DMFCs.
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