Pt-decorated SnO ₂ nanotubes prepared directly on a conducting substrate and their application in solar energy conversion using a solid polymer electrolyte

We report the electrostatic decoration of Pt nanoparticles on SnO ₂ nanotubes (ST) directly prepared on a conducting substrate and high electrocatalytic activities of the resulting materials. A pre-coating of poly(vinyl acetate) (PVAc) is the key for the direct uniform deposition of the ST, which serves dual functions as a fast electron transport path as well as a physical support for Pt nanoparticles. The self-assembly of Pt nanoparticles on the ST is based on electrostatic interaction between the Pt cations and negatively charged ST surface. A dip-coating method leads to homogeneous decoration of well-connected Pt nanoparticles with a larger surface area. Solar energy conversion devices with a solid polymer electrolyte are fabricated using Pt on ST as the electrocatalyst for the reduction of I ₃ ⁻ to I ⁻ . The Pt dip-coated ST shows a photovoltaic efficiency of 5.07%, which is higher than those of Pt spin-coated ST (4.88%) and Pt spin-coated on the substrate without ST (4.59%). An increase in the Pt concentration leads to further improvement in the efficiency up to 5.51%, which is a moderate value for solid electrolyte devices. The improved performance is attributed to the decreased electron transfer resistance and increased surface area of the electrode.