Bi-hierarchical porous Pt microspheres grown on Ti wire with TiO2nanotubes layer for selective alcohol sensing

Abstract

This study focuses on the synthesis of bi-hierarchical porous Pt microspheres directly on titania nanotube arrays grown on a Ti wire for their application as a one-electrode selective alcohol sensor. We evaluate the synthesis conditions, morphology, structure of the obtained material using scanning, transmission electron microscopy, and electron diffraction. The sensor performance is assessed in a one-electrode configuration, using thermocycling both to heat and acquire a signal that we further process with a machine learning algorithm for selective determination of alcohols. We found that reduction of Pt precursor by formic acid facilitates the appearance of quasi-1D Pt structures without using any surfactant. High excess of formic acid yields the formation of quasi-dendritic Pt structures with the overall morphology of a sphere and channels whose diameter remains one of the TiO2 nanotubes. Our data suggest the growth of Pt spheres to be diffusion-controlled with constant or decreasing nucleation rate that should include assembling of Pt nanorods. The fabricated sensors based on the synthesized structures show a chemiresistive response to methanol, ethanol, and isopropanol vapors in the mixture with air, which we selectively determine using only one sensor.