A high-sensitivity room-temperature hydrogen gas sensor based on oblique and vertical ZnO nanorod arrays

The high surface area to volume ratio, the networks connections of vertically and oblique nanorod arrays, and the absence of seed layer, were the key factors responsible for the high sensitivity of ZnO nanorod arrays based hydrogen sensor at room temperature. Arrays of vertical and oblique zinc oxide nanorods were grown on a c-plane sapphire substrate by microwave-assisted chemical bath deposition. Polyvinyl alcohol (PVA)–Zn(OH)2 nanocomposites were used as a novel seed material to seed the sapphire substrate prior to the growth of the ZnO nanorods. The hydrogen sensing capabilities of the ZnO nanorod arrays, without the use of a metal catalyst, were investigated at room temperature. The rods exhibited excellent sensitivity, of 500%, in the presence of 1000 ppm of H2 while consuming an ultralow level of power (<10 μW). The sensing measurements for hydrogen gas at various temperatures (25–250 °C) were repeatable over a period of 100 min. The sensor exhibited a sensitivity of 4000% at 250 °C upon exposure to 1000 ppm of H2 gas. Hysteresis was noticed in the sensor for different concentrations of H2 at different temperatures. It can be surmised that this hydrogen gas sensor has potential for use as a portable room-temperature gas sensor.