Metal–Organic Framework-Derived Co-Doped ZnO Nanostructures Anchored on N-Doped Carbon as a Room-Temperature Chemiresistive Hydrogen Sensor

Abstract

The impending need to utilize H2 for multiple applications has surged the need to develop H2 sensors. Development of selective and rapid room-temperature H2 sensors is an uphill task without the doping of precious metals (Pd, Pt, and Au) in semiconductor metal oxide (SMO) sensors. Nanostructure of the SMOs could play a decisive role in gas sensing properties of the material. In this study, metal–organic framework (MOF)-derived Co–ZnO anchored on nitrogen-doped carbon (Co–ZnO–N/C) nanomaterial has been demonstrated as an effective rapid room-temperature H2 sensor. The pyrolysis of monometallic ZIF-8 (Zn) gave rise to amorphous ZnO stabilized on nitrogen-doped carbon (ZnO–N/C) and was found to be innocent for H2 sensing, whereas the pyrolysis of bimetallic ZIF(Co–Zn) resulted in the formation of Co–ZnO–N/C nanostructure with a high dispersion of Co on amorphous ZnO. Co–ZnO–N/C inherited the nanostructure of the parent precursor with rhombododecahedron particles of 200–300 nm and possessed subnanometer pores. Co inclusion into ZnO has converted the innocent amorphous ZnO–N/C into a rapid room-temperature H2 sensor (by measuring the dynamic change in the resistance with respect to time). Co–ZnO–N/C displayed a 3.7% response % with 17–26 s of recovery–response times for 1% concentration of H2 under room-temperature conditions. The unique nanostructure of Co–ZnO–N/C enhanced the signal transduction (via N-doped carbon support) and promoted H2 diffusion (through subnanometer pores). Higher-temperature H2 sensing studies were also conducted at 200 °C, wherein Co–ZnO–N/C displayed an increase in response to 5.7% with 8–16 s of response–recovery times. Co–ZnO–N/C chemiresistor is a rare example that does not contain precious metals yet exhibits room-temperature hydrogen sensing.