Therefore, it is necessary to develop alternative materials which must be inert and show good catalytic effect in the electrolyte. A great deal of effort has been taken to replace the Pt metal with other materials such as cobalt sulfide (CoS) [16], titanium nitrides (TiN) [17–19], and carbon derivatives [20–23]. Among these candidates, carbon materials obtain increasing attention due to their abundance, low cost, and high catalytic activities with chemical stability against iodine redox couples [24–27]. Here, we focus on carbon black which is produced by combustion of heavy petroleum products with high surface areas. Compared to any other forms of carbon derivatives, carbon black

does not require a delicate process to apply to counter electrodes. Note that carbon nanotubes and nanorods require multiple operations for the synthesis and application on counter electrode substrates. In this work, we demonstrate the properties of carbon black material BKM120 with anatase TiO2 in an attempt to replace the Pt counter electrode in DSSC applications. Forty-nanometer-sized

TiO2 nanoparticles were tested with various weight ratios of carbon black, and the effect was investigated by electrochemical impedance spectroscopy and cyclic voltammetry analysis in detail. Methods Carbon black The carbon black chunk was purchased from Sigma-Aldrich (14029-U, St. Louis, MO, USA) and ground to make powder. Pulverized carbon black was sifted out with 80-unit mesh then calcined for LEE011 concentration 2 h at 500°C Glutamate dehydrogenase in a muffle furnace. The annealed carbon mass was ground again and passed through with 200- to 350-unit mesh for further heat treatment at 300°C for 2 h in order to remove the impurities. The final carbon black powder size was 80 nm. Anatase TiO2 nanocrystal synthesis Titanium dioxide nanoparticles in anatase crystal form were synthesized by a modified

Burnside method [28]. A 162-mL titanium (IV) isopropoxide (0.5 M, Sigma-Aldrich) was rapidly injected into 290 mL of distilled water (15.5 mol, J. T Baker, Avantor Performance Materials, Center Akt assay Valley, PA, USA) under stirring, and the solution was vigorously stirred for a further 10 h. Addition of titanium (IV) isopropoxide in such an aqueous solution results in a white precipitate in the TiOx form. The resultant colloid was filtered and washed thrice with 50 mL of deionized (DI) water. Then the filtrate was loaded into an autoclave with 30 mL of a 0.6 M tetramethylammonium hydroxide solution to form a white slurry. The pH of the colloidal solution after addition of the base was measured to be between 7 to approximately 8. The solution was heated to 120°C for 6 h in order to obtain a peptization, and then the peptized suspension was treated hydrothermally in the autoclave at a temperature of 200°C for 4.5 h. The colloids were centrifuged at 13,000 rpm for 40 min and the precipitate was dried for 1 day in a vacuum oven, then dissolved into the DI water (wt.% of DI water/TiO2 = 20:1).