Department of Materials Science and Engineering, Graduate School of Engineering, Kyoto University , Kyoto 606-8501, Japan.
Langmuir. 2017 Oct 17;33(41):10765-10771. doi: 10.1021/acs.langmuir.7b01688. Epub 2017 Oct 2.
Silicon is a promising electrode material for photoelectrochemical and photocatalytic reactions. However, the chemically active surface of silicon will be easily oxidized when exposed to the oxidation environment. We immobilized graphene oxide (GO) onto hydrogen-terminated silicon (H-Si) and reduced it through ultraviolet (UV) and vacuum-ultraviolet (VUV) irradiation. This acted as an ultrathin conductive layer to protect H-Si from oxidation. The elemental evolution of GO was studied by X-ray photoelectron spectroscopy, and it was found that GO was partially reduced soon after the deposition onto H-Si and further reduced after UV or VUV light irradiation. The VUV photoreduction demonstrated ca. 100 times higher efficiency compared to the UV reduction based on the irradiation dose. The saturated oxygen-to-carbon ratio (R) of the reduced graphene oxide (rGO) was 0.21 ± 0.01, which is lower than the photoreduction of GO on SiO substrate. This indicated the H-Si played an important role in assisting the photoreduction of GO. No obvious exfoliation of rGO was observed after sonicating the rGO-covered H-Si sample in water, which indicated rGO was immobilized on H-Si. The electrical conductivity of H-Si surface was maintained in the rGO-covered region while the exposed H-Si region became insulating, which was observed by conductive atomic force microscopy. The rGO was verified capable to protect the active H-Si against the oxidation under an ambient environment.
硅是一种很有前途的光电化学和光催化反应的电极材料。然而，当暴露在氧化环境中时，硅的化学活性表面很容易被氧化。我们将氧化石墨烯（GO）固定在氢化硅（H-Si）上，并通过紫外线（UV）和真空紫外线（VUV）辐照将其还原。这起到了一个超薄的导电层的作用，可以保护 H-Si 免受氧化。通过 X 射线光电子能谱研究了 GO 的元素演变，发现 GO 在沉积到 H-Si 上后很快就部分还原了，并且在 UV 或 VUV 光照射后进一步还原。基于辐照剂量，VUV 光还原的效率比 UV 还原高约 100 倍。还原氧化石墨烯（rGO）的饱和氧碳比（R）为 0.21±0.01，低于 SiO2 衬底上 GO 的光还原。这表明 H-Si 在辅助 GO 的光还原中起着重要作用。在水中超声处理 rGO 覆盖的 H-Si 样品后，没有观察到 rGO 的明显剥落，这表明 rGO 被固定在 H-Si 上。在 rGO 覆盖区域，H-Si 表面的电导率得以保持，而暴露的 H-Si 区域变得绝缘，这可以通过导电原子力显微镜观察到。实验证明 rGO 能够保护活性 H-Si 免受环境氧化。
