Yeonhoo Kim1,Taehoon Kim2,Tae Hyung Lee2,Yong Seok Choi2,Seungwoo Song1,Ansoon Kim1,Byung Hee Hong2,Ho Won Jang2
Korea Research Institute of Standards and Science1,Seoul National University2
Yeonhoo Kim1,Taehoon Kim2,Tae Hyung Lee2,Yong Seok Choi2,Seungwoo Song1,Ansoon Kim1,Byung Hee Hong2,Ho Won Jang2
Korea Research Institute of Standards and Science1,Seoul National University2
Hydrogen is a promising future energy source since it is clean, non-toxic, and renewable but explosive over a wide range, from 4 to 74 percent in ambient air. For this reason, the detection of hydrogen gas at an early stage is of great importance in varied research fields such as hydrogen storage systems, fuel cells, and water splitting. Although semiconducting metal oxides have been extensively explored for sensing applications, metal oxides are not suitable for flexible electronics. On the contrary, two-dimensional(2D) materials including graphene are promising alternatives to conventional sensing materials since they are entirely flexible and transparent. To modify the sensing characteristics of pristine 2D materials, various methods such as functionalization, composites, and noble metal decoration have been studied. Among the methods, noble metal decoration is one of the most facile methods to tune the sensing properties of 2D materials.<br/>In this work, we decorated palladium nanoparticles on graphene microchannels with electron beam evaporation to enhance the hydrogen sensitivity of the graphene layers. As the graphene layers are patterned with microchannels, the self-heating effect is induced by current crowding in the narrow electrical path. The self-heating effect enables to detect hydrogen gas at room temperature, which lowers power consumption by not using external heaters. The apparent temperature of the microchannel is characterized by an infrared camera. The hydrogen sensors exhibit good linearity, high sensitivity, and selectivity in a wide range of hydrogen gas concentrations from 1 to 50 ppm. The theoretical detection limit is calculated to be ~241 ppb. Moreover, the flexible sensors show stable sensing performance under mechanical bending strain. The ultralow detection limit and stability of the sensors broaden the potential use of Pd-decorated graphene microchannels for next-generation flexible/wearable applications.