Wang-Geun Shim

Enhanced photovoltaic properties of TiO2 film prepared by polycondensation in sol reaction

A TiO2 film of dye-sensitized solar cells was fabricated using a TiO2 sol prepared from titanium isopropoxide as a starting material. The effect of polycondensation time and temperature on physical and chemical properties of TiO2 film shows that the crystallinity, particle size, roughness, and surface area of TiO2 film can be successfully controlled by adjusting the polycondensation time and temperature in the synthesis process of the TiO2 sol. Adsorption properties (adsorption equilibrium, isosteric enthalpies of adsorption, and adsorption energy distributions) of N719 dye molecules on the prepared TiO2 film revealed that the short circuit current (Isc) and overall conversion efficiency (ηeff) are highly dependent on the crystallite size and the N719 dye adsorption properties. The TiO2 film has a pure anatase phase, high surface area including pore volume, and large anatase crystallite size and is capable of enhancing the photovoltaic performance. The energy conversion efficiency of the dye sensitized solar cells is highly dependent on the physical and chemical properties of TiO2 films.

Preparation of powdered activated carbon from rice husk and its methane adsorption properties

Success of adsorbed natural gas (ANG) storage process is mainly based on the characteristics of the adsorbent, so various synthesized adsorbents were analyzed for methane adsorption on a thermodynamic basis. Activated carbon from rice husk (AC-RH) was synthesized and its methane adsorption capacities were compared with phenol based activated carbons (AC-PH2O and AC-PKOH). The adsorption experiments were conducted by volumetric method under various constant temperatures (293.15, 303.15, 313.15 and 323.15 K) and pressure up to 3.5MPa. Maximum methane adsorption was observed in AC-RH as its surface area is higher than the other two adsorbents. The experimental data were correlated well with Langmuir-Fruendlich isotherms. In addition, isosteric heat of adsorption was calculated by using Clausius-Clapeyron equation.

Fine size-regulation of nanocrystalline anatase-TiO2via sol–gel synthesis and subsequent phase transformation by calcination

Nanocrystalline TiO2 particles were prepared via the sol–gel process. The particle size and nanostructure of the TiO2 sol were controlled through the ageing process accompanied by hydrolysis–polycondensation. The resultant TiO2 particles were analysed by BET, HR-TEM, PSA, TGA, turbidity, XRD, and zeta potential analyses. The TiO2 size increased with increasing ageing time and reaction temperature. A phase transformation from anatase to rutile occurred with heat treatment at 500 °C. The phase transformation is strongly influenced by the primary particle sizes of TiO2, which were characterised via XRD and Raman spectroscopic analyses.

Surface heterogeneity analysis of MWCNT from methane adsorption isotherms for adsorbed natural gas storage

Adsorption equilibria of methane on multi-walled carbon nanotube (MWCNT) were measured. For comparison of the adsorption properties, two zeolites (DAY and HSZ-320) were chosen. The isotherm data were obtained using a static volumetric method at 303.15 K, 313.15 K, 323.15 K and at pressures up to 3 MPa. Experimental data of zeolites and carbon nanotube were correlated by the Sips isotherm and the hybrid Langmuir-Sips equations, respectively. Isosteric enthalpies of adsorption were calculated as a function of surface loading.