Carbohydrate‐Derived Carbon Sheaths on TiO₂ Nanoparticle Photoanodes for Efficiency Enhancement in Dye‐Sensitized Solar Cells

Abstract

Nanostructured carbons have an essential function as catalyst supports, dopants, and additives for enhancing the electrochemical performances in the fi eld of energy and environmental science including dye-sensitized solar cells (DSSCs), fuel cells, Li-ion batteries, and photocatalysis based on low cost, excellent electronic conductivity, and high surface area. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Graphenes, carbon nanotubes (CNTs), and graphite-like carbonaceous materials, which are derived from hydrocarbon gases and polymers, have been used in DSSCs to improve the photon fl ow, electron transfer, and collection at both the photoanode and cathode. [ 1,[3][4][5]8,[10][11][12][17][18][19][20] The carbonization of carbohydrates has been investigated from the fi rst decades of the 20th century. [ 21,22 ] In most cases, carbohydrates were converted into carbons by hydrothermal method, which is performed in aqueous solutions in the mild temperature region (below 250 °C) at high pressure in closed systems. [21][22][23][24][25] However, carbohydrates could also be transformed into carbons by simple heat treatment around 400-500 °C under inert atmosphere. [ 26,27 ] According to previous studies, carbons originated from glucose, sucrose, and starch were generated by the polymerization and aromatization of carbohydrate molecules, which accompany the sequential intermolecular dehydration and condensation reactions between the hydroxyl groups of carbohydrates. [ 21,25 ] Compared with other carbonization methods, the utilization of carbohydrates as a carbon precursor has advantages in that 1) the sources are economic and eco-friendly; 2) the formation of homogeneous hybrid mixture with other materials is easy in solution due to a high solubility in water and alcohols; 3) the conversion into carbons can take place at a relatively lower temperature region without catalysts; 4) complicated synthetic procedures using explosive gases, strong acids or bases, and tedious washing steps can be excluded; 5) carbonization can be carried out even in air as well as under inert atmosphere; and 6) especially for the application in DSSCs, inhomogeneous dispersion of carbon materials or the formation of aggregates throughout TiO 2 photoanode can be prevented by introducing carbohydrates in liquid state in water and alcohols, which are used as solvents for the preparation of TiO 2 paste.Previous work showed that carbohydrates have been extensively exploited for the synthesis of carbons in energy and environment-related technologies such as photocatalysis, fuel cells, and Li-ion batteries; however, few attempts to generate DSSCs equipped with carbon-integrated photoanode based on the carbonization of carbohydrates have been made. [ 23,24,27 ] Here, we report a simple yet robust strategy to improve the DSSC performance by incorporating carbohydrate-based carbons as depicted in Scheme 1 .Glucose is dissolved into a mixture solution of water and ethanol, which is used to disperse TiO 2 nanoparticles (NPs) and prepare paste-like ...

Carbonaceous Dye‐Sensitized Solar Cell Photoelectrodes

“…Preparing carbons from the carbohydrates has many advantages including a lack of toxicity, a facile synthesis process, use of relatively low temperature coupled with economic viability. Due to these advantages, Jang and co‐workers used a glucose‐based carbon incorporated TiO 2 photoelectrode film (see Figure ) for DSSC . The J sc and PCE of the DSSCs containing glucose/TiO 2 photoelectrode were increased by 20.9% and 11.6%, respectively, as compared to those of the conventional DSSC.…”