Figure1. a) Top-view, b) cross-sectional SEM images, c) cross-sectional TEM image, d) EDS line scans and e) HRTEM image of the as-prepared G-Ni3SxO2-x/p-Si photocathode. XPS depth profiling on the G-Ni3SxO2-x/p-Si photocathode for f) Ni 2p, g) S 2p and h) O 1s at the surface, middle and bottom of the G-Ni3SxO2-x layer. i) Depth profile of atomic concentrations for G-Ni3SxO2-x. G-Ni3SxO2-x/p-Si光阴极的结构通过SEM、TEM、XPS等手段进行表征,文章中有详细的介绍。通过TEM和XPS测试我们发现,G-Ni3SxO2-x是由表层高质量的Ni3S2多孔层以及致密的NiOx底层组成。
Figure 2. a) PEC LSV curves and b) the corresponding ABPE of the p-Si, Ni3S2/p-Si and G-Ni3SxO2-x /p-Si photocathodes in 1 M NaOH solution under AM 1.5G one sun illumination. c) Electrochemical LSV curves and d) the corresponding Tafel plots of Ni3S2 and G-Ni3SxO2-x supported on NF in 1 M NaOH.
Figure 3. a) Comparison of energy level diagrams for p-Si, Ni3S2 and G-Ni3SxO2-x. b) Mott-Schottky plots taken on the Ni3S2/p-Si and G-Ni3SxO2-x/p-Si photocathodes. c) Nyquist plots for Ni3S2/p-Si and G-Ni3SxO2-x/p-Si recorded at 0.3 VRHE. d) Plots of charge transfer rate constant () and charge recombination rate constant () under different applied potential (solid lines represent and dashed lines represent ). e) Measurements of water contact angles for Ni3S2/p-Si and G-Ni3SxO2-x/p-Si. Insets display the images of water droplets. f) The average diameter of bubbles released on the Ni3S2/p-Si and G-Ni3SxO2-x/p-Si photocathodes. 通过PEC性能测试,G-Ni3SxO2-x/p-Si光阴极在1 M NaOH电解液中表现出较高的起始电位(Von=0.39 VRHE)和短路电流(J0=33.8 mA/cm2),取得了3.9%的能量转换效率。其性能要远远优于Ni3S2/p-Si,是目前性能最好的p-Si基光阴极。优异的性能在电催化方面也得到了证实。此外,G-Ni3SxO2-x不仅提供丰富的析氢反应活性位点,同时促进了电荷的分离、传输以及反应过程中气泡的释放。
Figure 4. a) PEC stability measurements for Ni3S2/p-Si and G-Ni3SxO2-x/p-Si. Confocal Raman spectra recorded from nine locations on the b) G-Ni3SxO2-x/p-Si and c) Ni3S2/p-Si photocathodes. G-Ni3SxO2-x/p-Si在1 M NaOH电解质中能稳定工作120 h且性能没有明显衰减。优异的稳定性归因于G-Ni3SxO2-x和p-Si基底有着良好的接触,且能够有效释放薄膜之间的应力。 以上研究工作以Gradient-Structuring Manipulation in Ni3S2 Layer Boosts Solar Hydrogen Production of Si Photocathode in Alkaline Media为题目,发表在ADVANCED ENERGY MATERIALS期刊。