Amorphous Bimetallic Cobalt-Based Transition-Metal Oxides for Gas Sensing Application with Regulated Selectivity

Amorphous materials have great potential application in gas sensors due to their abundant active sites. However, it is still a challenge to regulate their sensing performance. In this work, we developed a synthesis method of amorphous bimetallic cobalt-based transition-metal oxides, which were prepared via two steps, namely, coprecipitation of bimetallic hydroxides and then annealing at elevating temperature. Sn, Mg, and Zn as the second metal were introduced to prepare amorphous CoSn-O, CoMg-O, and CoZn-O. They were further used to fabricate gas sensors. A sensing investigation revealed that the sensors present different sensing behaviors, in which the CoSn-O, CoMg-O, and CoZn-O sensors show selectivity to TEA, EtOH, and n-BuNH₂, respectively. A sensor array based on these three types of sensors was constructed. The actual concentrations of the mixing gases of TEA, EtOH, and n-BuNH₂ can be obtained by matrix calculation with an error value of less than 10%. Finally, the sensing processes were discussed, and the sensing mechanism can be attributed to the surface resistance control model. This research affords a convenient method to synthesize amorphous bimetallic oxides with regulated properties for sensing application.