RESUMEN
Highly efficient metal-organic framework (MOF)-based oxygen evolution reaction (OER) catalysts are desirable for water splitting, but their development remains challenging due to poor accessibility of coordinatively unsaturated metal (cum) sites and low intrinsic activity. A large-area three-dimensional (3-D) macroporous interconnected nanosheet array of Ni-1,3,5-benzenetricarboxylate has been in situ self-assembled on Ti mesh (TM) by using ethanol as the solvent and high-affinity oxide layer on TM to promote in situ nucleation. The obtained nanoarchitecture exhibits much superior catalytic activity compared to most reported catalysts including MOF-based catalysts, other precious-metal-free ones, and Ir/Ru-based ones. Additionally, this electrode undergoes no current decay after 300 cyclic voltammetry (CV) cycles and can maintain at 250 mA cm-2 for over 266 h. The excellent catalytic performance is mainly due to the 3-D macroporous and interconnected nanosheet array structure improving cum site exposure and charge transport and in situ activated cum cations enhancing OH- adsorption. This work not only develops a facile and economical approach to synthesize 3-D macroporous interconnected MOF nanosheet arrays to simultaneously increase the number, exposure, and intrinsic activity of active sites and facilitate charge transport for high-performance eletrocatalysis, but provides scientific insights into the mechanisms for self-assembly of this unique nanoarchitecture and for the high OER performance.
RESUMEN
Recently, the inherent piezoelectric properties of the 2D transition-metal dichalcogenides (TMDs) tin monosulfide (SnS) and tin disulfide (SnS2) have attracted much attention. Thus the piezoelectricity of these materials has been theoretically and experimentally investigated for energy-harvesting devices. However, the piezoelectric output performance of the SnS2- or SnS-based 2D thin film piezoelectric nanogenerator (PENG) is still relatively low, and the fabrication process is not suitable for practical applications. Here we report the formation of the SnS2/SnS heterostructure thin film for the enhanced output performance of a PENG using atomic layer deposition (ALD). The piezoelectric response of the heterostructure thin film was increased by â¼40% compared with that of the SnS2 thin film, attributed to large band offset induced by the heterojunction formation. Consequently, the output voltage and current density of the heterostructure PENG were 60 mV and 11.4 nA/cm2 at 0.6% tensile strain, respectively. In addition, thickness-controllable large-area uniform thin-film deposition via ALD ensures that the reproducible output performance is achieved and that the output density can be lithographically adjusted depending on the applications. Therefore, the SnS2/SnS heterostructure PENG fabricated in this work can be employed to develop a flexible energy-harvesting device or an attachable self-powered sensor for monitoring pulse and human body movement.
RESUMEN
Two-dimensional (2D) nanomaterials have distinct optical and electrical properties owing to their unique structures. In this study, smooth 2D amorphous tin disulfide (SnS2) films were fabricated by atomic layer deposition (ALD), and applied for the first time to photoelectrochemical water splitting. The optimal stable photocurrent density of the 50-nm-thick amorphous SnS2 film fabricated at 140 °C was 51.5 µA/cm2 at an oxygen evolution reaction (0.8 V vs. saturated calomel electrode (SCE)). This value is better than those of most polycrystalline SnS2 films reported in recent years. These results are attributed mainly to adjustable optical band gap in the range of 2.80 to 2.52 eV, precise control of the film thickness at the nanoscale, and the close contact between the prepared SnS2 film and substrate. Subsequently, the photoelectron separation mechanisms of the amorphous, monocrystalline, and polycrystalline SnS2 films are discussed. Considering above advantages, the ALD amorphous SnS2 film can be designed and fabricated according to the application requirements.