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Preparation Of Carbide Molybdenum Electrocatalyst Based On Polyoxometalate And Its Application In The Counter Electrode Of Dye-sensitized Solar Cells

Posted on:2019-10-27Degree:MasterType:Thesis
Country:ChinaCandidate:T WangFull Text:PDF
GTID:2371330563453807Subject:Inorganic Chemistry
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It is one of the challenges of the 21st century to produce renewable clean energy in order to cope with environmental problems and the energy crisis.Among many renewable energy sources,solar energy has been paid more and more attention because of its rich resources,unique advantages and great potential for development.Most of the current energy supplies are ultimately derived from sunlight.Dye-sensitized solar cells?DSSCs?are regarded as promising solar cells for the next generation of photovoltaic technologies and have become research hotspots in the PV field.The counter electrode?CE?,as an important part of the DSSCs,collects electrons from the external circuit and catalyzes the redox reduction in the electrolyte,which has a significant influence on the photovoltaic performance,long-term stability and cost of the devices.Although the precious metal platinum?Pt?is an excellent CE electrocatalyst in traditional DSSCs,it has many disadvantages in practical application.On the one hand,the slow kinetics of I3-reduction requires Pt catalyst with high loading,which will undoubtedly increase the cost of DSSCs and bring a huge economic burden to the development of DSSCs.On the other hand,the dissolution and corrosion of Pt in I3-/I-electrolyte will result in the collapse of electrode structure,which will affect the catalytic activity of the electrode and the photovoltaic performance of DSSCs,thus shorten the lifetime of DSSCs.Therefore,solving the collapse of electrode structure and finding materials with low cost,good stability and high catalytic activity for electrode has been widely concerned by researchers all over the world.Polyoxometalates?POMs?are a kind of inorganic polyoxometallic cluster anions with various composition,structure and chemical properties,which have potential applications in the field of electrocatalysis,photocatalysis,pharmacy and food detection.In addition,POMs have advantages of stable structure and high catalytic activity and can undergo a stepwise multi-electron reversible redox process without any structure changes,which can be widely used in the CE of DSSCs and may have a broader market prospect for its development.In this paper,the nitrogen-doped carbon-supported molybdenum carbide nanocomposite electrocatalysts were prepared by means of the rich elemental composition and nanostructure of POMs,and further used as CEs for DSSCs.The compsites showed high stability and high performance in electrocatalysis.And the stable,efficient and reusable CEs were expected to replace the conventional Pt CEs.The specific work is as follows:1.A series of Mo2C@NC electrocatalysts were prepared through a one-step solid-state synthesis method between[?NH4?6Mo7O24]and C2H4N4.By changing the mass ratio of the two kinds of raw materials,the composites S-Mo2C-1/3,S-Mo2C-1/4 and S-Mo2C-1/5 were prepared,respectively.The diffraction peaks in the XRD measurements correspond to each crystal plane of Mo2C?no.350 787?.High resolution transmission electron microscopy?TEM?shows that the Mo2C nanoparticles are uniformly distributed on the nitrogen-doped carbon layer.Energy dispersive x-ray spectroscopy?EDX?shows that the complex is composed of Mo,C and N elements without any other impurities.The active components and structure analysis show that the composite catalysts may have high effective catalytic activity for the reduction of I3-and can improve the photovoltaic performance of DSSCs.2.Exploring the catalytic performance of Mo2C@NC complex electrocatalyst for DSSCs.The catalytic activity of different composite materials for I3-reduction reaction was compared by current density-voltage test,cyclic voltammetry test,electrochemical impedance test and tafel test.The results show that S-Mo2C-1/4 has the highest electrocatalytic activity and the lowest charge transfer impedance for I3-reduction,which is beneficial to accelerate the reaction rate of redox reaction in electrolyte,promote the recycling regeneration of dye molecules and improve the photovoltaic performance of DSSCs.The photovoltaic performance of the DSSCs based on S-Mo2C-1/4 CE can reach 6.49%,which is comparable to that of Pt?6.38%?.
Keywords/Search Tags:Dye-sensitized solar cells, Polyoxometalates, Counter electrode, Photovoltaic performance, Molybdenum carbide
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