Effects of poisoning gases on and restoration of PdCuSi metallic glass in a capacitive MEMS hydrogen sensor

We investigated the effects of poisoning and restoration of PdCuSi-metallic glass (MG), which is a sensing material that offers low power consumption and fast response times when used in capacitive MEMS hydrogen sensors. Four poisoning gases were used: hexamethyldisilazane (HMDS), H2S, SO2, and NO2. Exposure to H2S resulted in metal sulfide forming at the surface of the PdCuSi-MG, although the sulfur did not diffuse into the PdCuSi-MG. Exposure to NO2 only resulted in the nitrogen being adsorbed without bonding to metals. The poisoning elements were desorbed by heating. Exposure to H2S and SO2 degraded the hydrogen sensitivity in terms of resistance of the PdCuSi-MG, although exposure to HMDS and NO2 only slowed down the response time. These degradations were recovered by heating. We next examined forming a refresher layer under PdCuSi-MG in a hydrogen sensor. The hydrogen sensitivity of the H2S-exposed hydrogen sensor was restored by performing a refresh operation for a few minutes. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.