A novel hydrogen-sensitive sensor based on Pd nanorings/TNTs composite structure

Hydrogen sensors with a novel composite structure comprised of Pd nanorings distributed on TiO₂ nanotube arrays were developed and tested. Effect of the TiO₂ nanotube diameter size, Pd nanorings thickness on the sensors' hydrogen response characteristics were investigated. Time dependence of resistance of the Pd nanorings/TNTs composite structure on various hydrogen concentrations was also carried out and demonstrated good room temperature hydrogen sensitive characteristics. Optimized experiments demonstrated that the hydrogen sensor composed of 25 nm-thickness Pd nanorings distributed on the 77 nm-diameter size TiO₂ nanotube showed a fast response time (3.8 s) and high sensitivity (92.05%) at 0.8 vol% H₂. A hydrogen sensitive characteristics model is proposed and the Pd nanorings' important role in the hydrogen sensitive mechanisms is described. The hydrogen sensor's excellent hydrogen sensitive characteristics is ascribed to the Pd nanorings' quick and continual formation and breakage of multiple passages due to absorption and desorption of hydrogen atoms.