High temperature selective sensing of hydrogen with MgO-modified SrMoO4 micro-fibers

Micro-fibers of Mg-doped SrMoO4 (SrMoO4/MgO) were synthesized using a two-step hydrothermal technique. The SrMoO4/MgO micro-fibers were used as the sensing material within a solid-state, resistive-type sensor architecture. The material showed selective detection of hydrogen (H2) up to 1000 °C with high sensor response and stability for the given concentrations. The maximum relative resistance change values (Rmax) for SrMoO4/MgO for 4000 ppm H2 in a N2 atmosphere (1% O2) were −31, −85, and −87.5 for 600, 800 and 1000 °C, respectively. At 1000 °C, and the same background atmosphere, the Rmax was only −2.5 and −12.5 to 4000 ppm CO and 2000 ppm SO2, respectively. Chemical characterization showed that the Mg was dissolved into the SrMoO4 structure, in addition to residual MgO precipitate found within the final SrMoO4 powder. The surface MgO was shown to affect the H2 adsorption and dissociation processes in addition to high selectivity for H2 in comparison to SO2 and CO, while the dissolved Mg contributed to the alteration of the electronic properties, where the Schottky barrier height, band gap, and work function were all lowered. These combined effects resulted in the favorable sensitivity and high selectivity to H2, and also contributed to the increased stability at the elevated sensing temperatures.