The effects of Cu-content on Mg 2 Cu x Fe 1 O 3.5+x electrodes for YSZ-based mixed-potential type NH 3 sensors

Abstract Yttria-stablized zirconia (YSZ)-based mixed-potential type NH 3 sensors using Mg 2 Cu x Fe 1 O 3.5+ x mixed metal oxides ( x =0, 0.25, 0.50, 1) as sensing electrode material were fabricated for ammonia (NH 3 ) detection at different working temperatures ( T =350 °C, 400 °C, 450 °C, 500 °C). The Mg 2 Cu x Fe 1 O 3.5+ x electrodes were characterized by X-Ray Diffraction (XRD), Environmental Scanning Electron Microscope (ESEM), Energy Dispersive Spectrometer (EDS) and the Brunauer–Emmett–Teller (BET) method. The effects of Cu-content on phase composition, microstructures, NH 3 response performances and electrochemically catalytic-activity of Mg 2 Cu x Fe 1 O 3.5+ x electrodes were discussed. Magnesium copper oxide (Mg 0.78 Cu 0.22 O) may be a functional phase that improved NH 3 sensitivity of Mg 2 Cu x Fe 1 O 3.5+ x electrodes, but magnesium dicopper oxide (Cu 2 MgO 3 ) played an opposite role as a suppressive phase. The Mg 2 Cu 0.25 Fe 1 O 3.75 electrode exhibits the biggest response (about 267 mV for 200 ppm of NH 3 ), the highest NH 3 sensitivity (220 mV/decade NH 3 ) and the highest electrochemically catalytic-activity may be attributed to its suitable Cu-content for functional phase (Mg 0.78 Cu 0.22 O) with higher NH 3 adsorptivity, which can absorb more NH 3 to the triple-phase boundary (TPB) for the electrochemically reaction.