Exploring Sb2Se3 as a photoelectrochemical (PEC) photocathode for water reduction has recently attracted much attention, mainly due to its excellent photophysical properties and perfect band structure matching with water reduction potential. Whereas significant achievements have been made in improving its photocurrent density, the PEC performance remains poor mostly due to the low onset potential or low fill factor. Here, we fabricated S doped Sb2Se3 nanowire arrays with a gradient S concentration (grad-S:Sb2Se3). Gradient S doping creating a cascade valence band structure in Sb2Se3 simultaneously enhances its onset potential and fill factor. Light-trapping effects in nanowire geometry improve the light harvesting efficiency. A further deposition of a thin TiO2 layer is utilized to passivate the detrimental surface defects and form a buried junction with grad-S:Sb2Se3. By employing the prepared grad-S:Sb2Se3 nanowire arrays as the photocathode for water reduction, we achieved a high onset potential of 0.42 V vs RHE, a fill factor of 34%, and a record high half-cell solar-to-hydrogen conversion efficiency of 2% from Sb2Se3-based photocathodes.
Polypyrrole complex nitrogen-doped porous carbon matrix (PPy/N-PCM) was synthesized by a simple two-step method. Firstly, graphene oxide was prepared by the modified Hummers method. Secondly, Polypyrrole was compounded on the graphene oxide substrate, and the carbon matrix with a high specific surface area was obtained through high-temperature carbonization and KOH activation, and polypyrrole was used as a nitrogen source for the final nitrogen-doped composite material. The structure characterization of the carbon matrix and the final composite material shows that the carbon matrix surface has obvious porous structure, and the polypyrrole nanospheres grow uniformly on the porous carbon matrix surface. The electrochemical evaluation show that the prepared PPy/N-PCM has excellent supercapacitor performance, and its specific capacitance can reach 237.5 F g−1. When the current density reaches 10 A g−1, it has good cycle stability (the capacitance retention after 1000 charge and discharge is 88.53% of the initial capacitance value, which is better than pure PPy-60.76% and PPy/rGO-C-71.84%). The excellent capacitance performance, good-looking micro-morphology and simple synthesis method of the PPy/N-PCM provide the possibility for its commercialization.
Azobenzene molecules show excellent application potential in many fields due to their photoisomerization properties. Azobenzene molecules will gradually change from trans-structure to cis-structure under the irradiation of UV. In this paper, we have synthesized 4,4'-dibromoazobenzene molecules and characterized their photoisomerization properties. We found that with the extension of UV time, the trans absorption peak at 343 nm decreased significantly, while the cis absorption peak at 435 nm showed an upward trend. Furthermore, photoisomerization of azobenzene is not a first-order reaction.
Graphene oxide (GO) was prepared using the modified Hummers method and used as a template for polypyrrole. Polypyrrole was polymerized in situ on the surface of GO to finally obtain the polypyrrole/graphene oxide composite material. The effects of different reaction times on the electrochemical performance of polypyrrole/graphene oxide in the second step were studied. It was obtained that the composite material had optimal properties when the reaction time was 24 h.
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