The practical application of dye-sensitized solar cells (DSCs) requires high photovoltaic efficiency and good photovoltaic stability. This work reports nanocomposites of two-dimensional graphene oxide (GO) and one-dimensional multi-walled carbon nanotubes (MWCNTs) as the gelator of gel electrolytes for quasi-solid state DSCs. The composite gels are formed by immobilizing an organic solvent, 3-methoxypropionitrile (MPN), with GO and MWCNTs, and the gel electrolytes are prepared by adding iodine, 1-methyl-3-propylimidazolium iodide, guanidinium thiocynate and 4-tert butylpyridine into the GO-MWCNT-MPN composite gels. GO sheets can gel organic solvents because of their hydrophobic and hydrophilic domains. The MWCNTs can reinforce the solid networks formed by GO sheets and reduce the ionic diffusion length of the redox species within the electrolyte as MWCNTs are conductive and catalytic toward the electrochemical reduction of I 3 À . The presence of MWCNTs in the gel electrolyte increases both the open-circuit voltage (V OC ) and the short-circuit current (J SC ) of DSCs so as to increase the power conversion efficiency (PCE). The optimal PCE of the DSCs with GO-MWCNT-MPN gel electrolyte is 7.12% under AM 1.5G illumination (100 mW cm À2 ), which is significantly higher than that (6.54%) of the gel DSCs without MWCNTs.
Noble metals such as platinum are excellent catalysts. Increasing the surface area of these metal catalysts is important for their practical application. We report a facile method to directly deposit skeletal platinum nanostructures through the chemical reduction of its precursor. Although porous platinum structures can be deposited on a substrate through the chemical . The electrocatalytic activity also increases significantly.Pt has excellent catalytic activity in many chemical reactions and superior resistance to corrosion in various environments. [1,2] It has important application in many areas, including the chemical, petrochemical, pharmaceutical, electronic, and automotive industries. For example, Pt and its alloys are the most important catalysts in many electrochemical reaction systems. [3,4] The exploitation of Pt or Pt alloys as catalysts for electrochemical conversion systems such as fuel cells and dye-sensitized solar cells can give rise to high energy conversion efficiency. [5][6][7][8][9] They are also highly active as catalysts in the conversion of vehicle exhausts such as CO and NO x into CO 2 and N 2 , respectively. Their high catalytic activity in some chemical and biochemical reactions leads to their application in chemical sensors and biosensors. However, as Pt is a noble metal, its high price severely impedes its application and the commercialization of some systems such as fuel cells. The Pt usage can be lowered remarkably by using porous Pt with a high specific surface area. There are three main strategies to prepare porous metals.[10-13] The first strategy is to prepare porous metals by using hard or soft templates. [14][15][16][17] Porous membranes such as aligned aluminum oxide and close-packed colloidal crystalline films have been exploited as hard templates. The soft templates include micelles, microemulsions, liposomes, and vesicles. The second strategy to prepare porous metals is the dealloying method, [18,19] in which the other species in an alloy are more chemically reactive than the target metal. The former are etched away by chemical or electrochemical oxidation. The third strategy is the assembly of metal nanoparticles or nanowires, [20][21][22][23][24][25] in which chemicals such as ionic liquids and peptides are used to assemble nanometer-sized metals into porous structures.The preparation of porous Pt nanostructures through a simple process is significant to their application as a catalyst in many areas. Here, we report a facile method to deposit skeletal Pt nanostructures with high surface area and high porosity through the chemical reduction of a Pt precursor by using (NH 4 ) 2 CO 3 . H 2 PtCl 6 and (NH 4 ) 2 CO 3 are deposited on the substrate from their solution. The (NH 4 ) 2 CO 3 decomposition gives rise to void space in H 2 PtCl 6 . The porous H 2 PtCl 6 converts into skeletal Pt nanostructures with high surface area and high porosity after it is chemically reduced by the vapor of ethylene glycol (EG).A solution consisting of H 2 PtCl 6 and (NH 4 ) 2 CO 3 was prepared...
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