nature, which cannot meet the increasing demand for its broad applications in DSSCs. Thus, there is a huge interest in Pt-free materials for CE fabrication, such as inorganic semiconductors, [5] carbon materials, [6] conductive organic polymers, [7] and so on. [8,9] Metal-organic frameworks (MOFs) represent a class of porous coordination polymers that consist of organic ligands linker by metal ions to form crystalline assemblies, [10,11] which have been widely investigated for their attractive physical and chemical properties. [12,13] Recently, the tunable functionality of MOFs has allowed these porous materials as precursors or sacrificial templates for the preparation of electrode materials in DSSCs. [14,15] In particular, porphyrin-based MOFs (also called metal-porphyrin frameworks) [16] have been demonstrated to exhibit tunable optical, electrical, and photophysical properties, [17][18][19] which in particular suggest applications in DSSCs. However, up to now, employing metal-porphyrin frameworks for CE materials in DSSCs has not been reported.When aiming to use the potential of MOFs for electrical, electrochemical, and electronic applications, MOF thin films [20][21][22] prepared by a layer-by-layer (lbl) liquid-phase epitaxial (LPE) procedure have attracted huge interest. These surfacemounted MOFs or SURMOFs are assembled by a sequence of simple immersion processes, subsequently into solution of the metal source and the organic ligand. They exhibit a number of interesting properties, including controllable thickness, crystallinity, high degree of orientation, and homogeneous surface. So far, the lbl-approach has been successfully used to realize several types of SURMOFs, [23] e.g., HKUST-1 (Cu 3 (BTC) 2 , BTC = benzene-1,3,5-tri-carboxylate), SURMOF-2, Zn(2-methylimidazolate) 2 (ZIF-8), etc. [23][24][25] These SUR-MOFs are epitaxially grown on appropriately functionalized substrates by coordination bonding between metal ions and organic ligands. The growth of SURMOFs based on lbl protocols involving noncovalent interactions (such as van der Waals, hydrogen bonding, and other weak interactions, etc.) has not yet been studied. When using porphyrinic ligands, such SUR-MOFs are expected to have interesting applications in catalysis, electronic devices, and in photovoltaics. [26][27][28][29][30][31][32][33][34] Herein, we report a layer-by-layer epitaxial growth strategy for preparing SURMOFs with a layered structure. 2D sheets consisting of paddle-wheel (PW) units linked by porphyrin linkers are stacked by the interaction between layers being of van der Waals type. X-ray diffraction (XRD) data reveal that layer-by-layer deposition on appropriately functionalized substrates yields In this work, monolithic, crystalline, porous, and oriented porphyrin thin films are grown using a novel van der Waals layer-by-layer (lbl) epitaxial growth protocol, yielding an unusual AB-stacking motif of these interesting macrocycles units. Subsequently, these surface-mounted metal-organic frameworks (SURMOFs) are transformed by th...
Bifacial dye-sensitized solar cells (DSSCs) are regarded as promising solar energy conversion devices with high efficiency and less resource consumption. In this work, a highly transparent and efficient counter electrode (CE) is fabricated by introducing highly dispersed single Pt atoms doped into the van der Waals layerby-layer epitaxially grown Zn-TCPP thin film (Zn-TCPP-Pt). The resulting Zn-TCPP-Pt CE has similar catalytic activity to commercial Pt CE but shows a better light transmission capacity in the range of visible light. The bifacial DSSC with Zn-TCPP-Pt thin film CE achieves high power conversion efficiencies of 5.48 and 4.88% under front-side and rear-side irradiation, respectively. With maximized atomic efficiency, excellent performance was obtained with about 1% Pt content and highly transparent CEs. Therefore, the light energy resource utilization rate of such less Pt and transparence CE is greatly improved in bifacial dye-sensitized solar cells, making it a promising candidate to replace Pt CE.
The design and development of the supercapacitors containing metal oxides and carbon materials is very important for energy-storage devices in laboratory and industry. In this study, we report a helical carbon tube material derived from epitaxial Cu-MOF coating on textile by calcination treatment. The electrochemical performance obtained from the cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and cyclic stability measurements indicates that such a hybrid carbon material with a unique structure has a very high areal capacitance of 1812 mF cm-2 at a current density of 1 mA cm-2, and the material also has a good recyclability of 90% after 2000 cycles. This study combines the advantages of MOF- and cotton textile-derived carbon materials, and this study can serve as a guidance to improve the capacitance performance of supercapacitors.
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