Role of tannic acid in desiging of electrically active and magnetic gold nanoparticles and enhanced photovoltaic performance of gold@titania photoanode in DSSC

Abstract

We describe here in significance of tannic acid in obtaining size dependent electrochemically active and magnetic gold nanoparticles (GNPs). In this account, two types of GNPs (SCGNPs and SC-TAGNPs) were synthesized by using sodium citrate and sodium citrate-tannic acid as reducing agents, respectively. Highly monodispersed, uniformly distributed and small size GNPs were produced when tannic acid was used together with sodium citrate. SC-TAGNPs exhibited room temperature ferromagnetism while SCGNPs revealed diamagnetism. With higher anodic peak current and lower charge transfer resistance, the SC-TAGNPs exhibited better conductivity and electron transfer ability than SCGNPs. Mott-Schottky analysis revealed n-type semiconducting behavior of GC/SCGNPs & GC/SC-TAGNPs and showed positive shift in flat-band potential of GC/SC-TAGNPs compared to GC/SCGNPs suggesting better conductivity of SC-TAGNPs. Subsequently, SCGNPs and SC-TAGNPs were added to TiO2 nanoparticles to fabricate modified titania photoanodes (SCGNPs@TiO2 and SC-TAGNPs@TiO2) for dye-sensitized solar cells (DSSCs) application. With the use of TiO2, SCGNPs@TiO2 and SC-TAGNPs@TiO2 photoanodes, the short-circuit current density (JSC) was observed to be 2.18, 4.50 and 6.68 mA/cm2, while energy conversion efficiency (η) was found to be 0.75, 1.74 and 2.50%, respectively. The TiO2 photoanode employing SC-TAGNPs exhibited remarkably increased JSC and η by ∼48 and ∼44%, respectively, then SCGNPs modified photoanode.