Silicon Nanowires Decorated with Silver Nanoparticles for Photoassisted Hydrogen Generation

Highly n-doped silicon nanowires (SiNWs) decorated with silver nanoparticles (AgNPs) at the top, middle, and bottom were produced using electroless silver deposition (ELD), silver mirror reaction (MR), and native AgNPs as a reference, respectively. Subsequently, hydrogen generation on SiNWs decorated with and without AgNPs was evaluated. Our results show that SiNWs decorated with native and MR AgNPs produce the highest and the lowest hydrogen amount under white light irradiation in 3 h, respectively. Moreover, for SiNWs with native AgNPs, the morphology of SiNWs after hydrogen generation was almost the same as the original array of SiNWs before hydrogen release, even after 24 h in water/ethanol (4:1; v/v) solution. However, the geometry of SiNWs decorated without and with AgNPs by ELD and MR was collapsed after hydrogen evolution. The detailed surface studies show that the sidewall surface of SiNWs with native AgNPs has a rougher topology and formed a stable layer of SiOx in water. Our observations strongly suggest that two hydrogen generation possibilities, i.e., SiNW oxidation and photostimulation, are jointly responsible for the efficient hydrogen generation. Additionally, the presence of AgNPs on the sidewall of the SiNW matrix can enhance the hydrogen generation rate. Our results open novel perspectives for the effective hydrogen generation based on nanostructured silicon.