Metal doping fabricated heterobimetallic nickel-zinc composites and its performance-enhancing sensitivity towards nitrogen dioxide

Abstract

Monitoring and detecting poisonous nitrogen dioxide (NO2) is greatly challenged by ambiguous knowledge about the sensing mechanism and structures of sensitive materials and reaction intermediates. In particular, synthetic strategies like doping and coupling, although do improve gas-sensing activity, have made the structural identification rather difficult. In the work, we have comprehensively examined nickel-doped zinc oxide (marked as ZON) and its material-coupled composites (ZON/Y) for sensing NO2 by density functional theory. The material (Y) varies from graphitic carbon nitride (CN), graphene (Gr) to cellulose (Cel). It is revealed that the metal doping greatly promotes the NO2 adsorption over the material coupling. This well reproduces the experimental findings that the Ni-doped ZnO has much faster response time than ZnO, ZnO/g-C3N4 and ZnO/graphene. Of all the studied SMs, ZON/CN exhibits superior NO2 gas-sensing performance. Along the reaction pathway, it gives NO2 adsorption free energy of − 0.860 eV, followed by the mildest uphill process of catching the second NO2 (0.320 eV) and the modest downhill process of forming nitrate (−0.680 eV). The large adsorption energy of the initial step is attributed to the fabricated heterobimetallic Ni-Zn sensing active sites. The better sensitivity of ZON/CN is further evidenced by analyses of structures and interfacial bondings.