Study of the structural evolution and gas sensing properties of PECVD-synthesized graphene nanowalls

This research paper reports on the study of the structural evolution and room temperature (RT) of ammonia (NH₃) gas sensing properties of 3D graphene nanowalls (GNWs). Large-area porous GNWs were directly prepared as sensing layers using the plasma enhanced chemical vapor deposition (PECVD) technique with an H₂/CH₄ gas mixture as the precursor. H₂ plasma etching not only contributes to the structural evolution and thickness of the maze-like nanowalls, but also plays important roles in the defect sites of the surface and the effective crystalline size of the PECVD-synthesized GNWs. Comparative studies of the sensing performance showed that the newly fabricated GNW sensors were highly responsive and selective to NH₃ gas with a low detection limit at RT. The charge transfer has been confirmed as being the dominant sensing mechanism of GNW sensors. The excellent sensing performance of the GNWs demonstrates that 3D assemblies of 2D graphene nanosheet structures with a high surface area, a large amount of defect sites, and small crystalline sizes are a promising candidate for gas sensing applications. (paper)