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A Self-Assembled Chromophore/Catalyst Bilayer for Water Oxidation in a Dye-Sensitized Photoelectrosynthesis Cell
摘要： A new approach is described here for the preparation of water oxidation photoanodes in a Dye-Sensitized Photoelectrosynthesis Cell (DSPEC) for water splitting. It is based on a chromophore (C) - catalyst (Cat) assembly prepared by a self-assembled bilayer (SAB) on a mesoporous SnO2/TiO2 core/shell electrode, FTO| SnO2/TiO2|-C-Cat. A key feature in the resulting assembly is the in-situ “synthesis” by utilization of non-covalent interactions between long alkyl substituents of the chromophore and catalyst components. The photoanode carries out photoelectrochemical water oxidation for more than 3 hours with ~ 86% faradaic efficiency for oxygen generation. At pH 7 under 1 sun illumination, the photoanode reaches a photocurrent density of ~2.2 mA/cm2 with an incident photon to current efficiency (IPCE) of 29% at 450 nm. With an injection yield of only ~ 42%, the efficiency of the cell, excluding the losses at the core/shell interface, is a remarkable 67 %.
关键词： water oxidation,photoelectrochemical,chromophore-catalyst assembly,dye-sensitized photoelectrosynthesis cell,self-assembled bilayer
更新于2025-09-19 17:13:59
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Recent Progress in Visible Light Driven Water Oxidation Using Semiconductors Coupled with Molecular Catalysts
摘要： Hybrid systems combining the molecular catalyst and semiconductors have been demonstrated to be feasible and efficient for water oxidation under visible light illumination. Herein, we present a brief review on recent developments of constructing molecule/semiconductor hybrid systems. These hybrid systems combined molecular catalysts with dye-sensitized semiconductors or visible-light-response semiconductors. This review systematically summarizes the fabrication strategies of hybrid systems in photoelectrochemical (PEC) water splitting and powdered photocatalytic water oxidation. Furthermore, we highlight the excellent water oxidation performances and stability of different hybrid systems and provide valuable guidance to design construction strategies for more robust and capable devices.
关键词： semiconductor,photoanode,molecular catalyst,photocatalytic,water oxidation,photoelectrochemical
更新于2025-09-19 17:13:59
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Self-Assembled Amphiphilic Molecules for Highly Efficient Photocatalytic Hydrogen Evolution From Water
摘要： Self-assembled molecules for outstanding hydrogen evolution rate and durability should promise practical water splitting due to the versatile visible light absorption, low production cost and ease of control. Here, we adapted an amphiphilic molecule as a building block for efficient small molecule based self-assembled photocatalyst for hydrogen evolution from water. The self-assembled molecules with platinum co-catalyst showed outstanding performance (turnover number ~ 27,000) virtually comparable to the state-of-the-art metal oxide based photocatalysts with catalytic activity extending over days. Transient absorption studies in combination with quantum chemical calculations revealed that elaborate excited state engineering of the molecules resulted in such high performance of hydrogen evolution from water. This study shows that the self-assembled amphiphilic molecules could pave the way to more economical and reproducible production of hydrogen from water.
关键词： Platinum co-catalyst,Amphiphilic molecule,Photocatalytic hydrogen evolution,Excited state engineering,Self-assembled molecules
更新于2025-09-19 17:13:59
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Role of nitrogen doped carbon quantum dots on CuO nano-leaves as solar induced photo catalyst
摘要： A p-type transition metal oxide, copper oxide (CuO) was modified with nitrogen doped carbon quantum dots (NCQDs) to fabricate an effective CuO/NCQDs solar driven photo catalyst. The fabrication of single phase monoclinic CuO was confirmed by XRD. SEM images showed the leaf like morphology for CuO which appeared rough and densely packed in CuO/NCQDs composites. TEM images of CuO/NCQDs shows slightly distorted nano-leaves with NCQDs dispersed on them. HRTEM of CuO/NCQDs shows fringes with characteristic planes confirming that the addition of NCQDs has not distorted the crystal structure of CuO. SAED of CuO/NCQDs further confirms the crystalline nature of the as synthesized composite photo catalyst by exhibiting bright diffraction rings. These results further supported the XRD data. EDS spectra of NCQDs and CuO/NCQDs confirm the formation of pure nitrogen doped carbon quantum dots and Cu, N, C and O atoms confirming that NCQDs are well incorporated on CuO Nano leaves. UV-Vis spectra showed a slight increase of band gap energies due to quantum confinement effects. PL spectra exhibited decreased photoluminescence intensity indicating suppression of recombination rate. The developed photocatalyst was applied for the degradation of harmful dye methyl orange. The composite catalyst showed superior degradation efficiency as compared to pure CuO nano-leaves attributed to enhanced visible light absorption and better charge separation ability due to introduction of NCQDs.
关键词： solar light catalyst,nitrogen doped quantum dots,charge separation efficiency,quantum confinement effect,CuO nano-leaves
更新于2025-09-19 17:13:59
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Fine-tuning of spark-discharge aerosol CVD reactor for single-walled carbon nanotube growth: the role of ex situ nucleation
摘要： We report a development of recently designed apparatus equipped with a spark discharge generator of catalytic nanoparticles for robust aerosol CVD synthesis of single-walled carbon nanotubes. We achieve a profound control over the diameter distribution and the defectiveness of carbon nanotubes produced. By providing a justified comparison of the apparatus with the most abundant aerosol CVD reactor utilizing ferrocene as a catalyst precursor, we reveal the role of the activation procedure: while spark-discharge generator provides aerosol of nanoparticles (ex situ route), the ferrocene vapor decomposes in the nanotube growth zone providing an in situ formation of the catalyst. With other parameters being equal, we reveal the differences in the nanotube growth (diameter and length distribution, yield, defectiveness) employing a comprehensive set of methods (the analysis of differential mobility of the aerosol particles, optical spectroscopy, scanning and transmission electron microscopy, Raman spectroscopy, and atomic force microscopy). We show the ex situ activation in the spark discharge reactor to provide a lower utilization degree of the nanoparticles due to over-coagulation. However, the same method provides an independence of the key performance parameters of the nanotubes opening a room for scaling the apparatus.
关键词： spark-discharge generator,differential mobility analyzer,aerosol CVD synthesis,catalyst activation,floating catalyst,single-walled carbon nanotubes
更新于2025-09-16 10:30:52
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Mg-Doped ZnO and Zn-Doped MgO Semiconductor Nanoparticles; Synthesis and Catalytic, Optical and Electro-Optical Characterization
摘要： A series of MgxZn1 – xO and ZnxMg1 – xO (mol %) were synthesized by the sol–gel method. All the synthesized nanoparticles were investigated as catalyst in the one-pot, three-component Biginelli condensation reaction of benzaldehyde, ethyl acetoacetate and urea under heterogeneous conditions. Findings revealed Mg0.007Zn0.093O (Zn7) as the best in the mentioned condensation reaction. Zn7 was characterized by FT-IR, SEM, CHN, and XRD. In addition, linear and nonlinear optical properties of MgxZn1 – xO and ZnxMg1 – xO thin films and their colloidal solutions were studied. Using an exact numerical method, some photo-physical properties of the prepared films such as dispersion curve, absorption spectrum, optical permittivity and optical band gap were attained and compared. Finally, using z-scan method at low laser irradiation, thermo-optical effect has also studied and a nonlinear refractive index due to this effect was attained. Doping effect on the optical properties was also investigated physically. It was found in both the particles groups, increasing the doping percent reduces the band gap and it suggests new optoelectronic materials with a spectrum of optical properties.
关键词： z-scan,ZnxMg1 – xO,MgxZn1 – xO,catalyst,optical band gap,nanoparticles,permittivity
更新于2025-09-16 10:30:52
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Chirality control for predominant metallic or semiconducting single-walled carbon nanotubes prepared using a mild etchant
摘要： Highly oriented metallic and semiconducting SWCNTs were synthesized with different carrier gas compositions and etchants by the floating catalyst chemical vapor deposition method. The addition of acetone as an etchant resulted in metallic nanotubes. The acetone acted as both an additional carbon source and etching agent for carbon nanotube nucleation.
关键词： Chirality control,Metallic,Floating catalyst chemical vapor deposition,Single-walled carbon nanotubes,Acetone,Semiconducting,Etchant
更新于2025-09-16 10:30:52
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<i>In situ</i> synthesis of monolayer graphene on silicon for near-infrared photodetectors
摘要： Direct integration of monolayer graphene on a silicon (Si) substrate is realized by a simple thermal annealing process, involving a top copper (Cu) layer as the catalyst and an inserted polymethylmethacrylate (PMMA) as the carbon source. After spin-coating the PMMA carbon source on the Si substrate, the Cu catalyst was deposited on PMMA/Si by electron beam evaporation. After that, graphene was directly synthesized on Si by decomposition and dehydrogenation of PMMA and the catalyzation effect of Cu under a simple thermal annealing process. Furthermore, under an optimized growth condition, monolayer graphene directly formed on the Si substrate was demonstrated. Utilizing the as-grown graphene/Si heterojunction, near-infrared photodetectors with high detectivity ((cid:1)1.1 (cid:3) 1010 cm Hz1/2 W(cid:4)1) and high responsivity (50 mA W(cid:4)1) at 1550 nm were directly fabricated without any post-transfer process. The proposed approach for directly growing graphene on silicon is highly scalable and compatible with present nano/micro-fabrication systems, thus promoting the application of graphene in microelectronic fields.
关键词： thermal annealing,PMMA,silicon,photodetectors,copper catalyst,graphene
更新于2025-09-16 10:30:52
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Single-walled carbon nanotube growth at low temperature by alcohol gas source method using Co catalyst: enhancement effects of Al<sub>2</sub>O<sub>3</sub> buffer layer on carbon nanotube yield
摘要： Using an alcohol gas source chemical vapor deposition method, we attempted to grow single-walled carbon nanotube (SWCNT) growth using Co catalysts on Al2O3 buffer layers. Reducing the growth temperature decreased the optimal ethanol pressure to obtain the highest SWCNT yield. By optimizing the ethanol pressure, we succeeded in growing SWCNTs at 400oC. Irrespective of the growth temperature, SWCNT yields from Co catalysts on Al2O3 buffer layers were higher than those on SiO2/Si substrates, but the enhancing effects of Al2O3 buffer layers on SWCNT yield were reduced below 500oC. Taking into account both in-plane X-ray diffraction results and decrease of catalyst aggregation in the low temperature region, we concluded that the density of Co particles suitable for SWCNT growth increased on SiO2 surface at low temperature, resulting in the reduction of difference in SWCNT yield at low temperature between Al2O3 buffer layers and SiO2/Si substrates.
关键词： catalyst,CVD,low-temperature growth,single-walled carbon nanotube,Co
更新于2025-09-16 10:30:52
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Simulation to fabricationa??understanding the effect of NiAuCu alloy catalysts for controlled growth of graphene at reduced temperature
摘要： It is a significant challenge to grow large-scale, high quality, monolayer graphene at low temperature for the applications in industry, especially for the complementary metal oxide semiconductor fabrication process. To overcome this difficulty, we simulated the decomposition of acetylene (C2H2) on (100) surfaces of primarily nickel (Ni) catalysts with small mol fractions of gold (Au) and copper (Cu), using a 4×4×4 periodic supercell model. Based on the calculation of the reaction energies to decompose the C-H or C≡C bonds on different catalyst surfaces, a differential energy is proposed to clearly scale the decomposition difficulties such that larger differential energy leads to easier control of the monolayer growth. It is observed that on the NiAuCu alloy surface with a mol fraction 0.0313 of both Au and Cu, the differential energy of the C-H bonds and the C≡C bond are both positive, showing an obvious modulation effect on the decomposition of C2H2 and the catalytic activites. The simulation result is consistent with the growth of uniform monolayer graphene on silicon dioxide substrate at 500°C by plasma enhanced chemical vapor deposition with C2H2 precursor and Ni alloy catalysts with 1 wt% Au and 1 wt% Cu.
关键词： NiAuCu alloy catalyst,chemical vapour deposition,graphene,density function theory,low temperature
更新于2025-09-16 10:30:52