Hydrogen-selective sensing at room temperature with ZnO nanorods

Abstract

The sensitivity for detecting hydrogen with multiple ZnO nanorods is found to be greatly enhanced by sputter-depositing clusters of Pd on the surface. The resulting structures show a change in room- temperature resistance upon exposure to hydrogen concentrations in ${\mathrm{N}}_2$ of $10–500\mathrm{ppm}$ of approximately a factor of 5 larger than without Pd. Pd-coated ZnO nanorods detected hydrogen down to $<10\mathrm{ppm}$ , with relative responses of $>2.6\%$ at $10\mathrm{ppm}$ and $>4.2\%$ at $500\mathrm{ppm}$ ${\mathrm{H}}_2$ in ${\mathrm{N}}_2$ after a $10\min$ exposure. There was no response at room temperature to ${\mathrm{O}}_2$ . Approximately 95% of the initial ZnO conductance after exposure to hydrogen was recovered within $20\mathrm{s}$ by exposing the nanorods to either air or pure ${\mathrm{O}}_2$ . This rapid and easy recoverability make the Pd-coated nanorods suitable for practical applications in hydrogen-selective sensing at ppm levels at room temperature with $<0.4\mathrm{mW}$ power consumption.