Recent Advances in Gas and Humidity Sensors Based on 3D Structured and Porous Graphene and Its Derivatives

Abstract

Compared with two-dimensional (2D) graphene sheets, recently, three-dimensional (3D) structured and porous graphene has attracted much attention in gas and humidity sensing owing to its increased specific surface area, abundant reaction sites, and superior sensing performance. This review begins with the introduction of the device configurations and working mechanisms of 3D graphene-based gas sensors, followed by the elaboration of various synthesis strategies of 3D graphene. In addition to the gas-transducing properties of 3D and suspended graphene, the modification effect of metal oxides, small molecules, conductive polymers, noble metal nanoparticles, 2D materials, etc. on the gas-sensing performance of 3D graphene is also systematically discussed. 3D structured graphene not only performs as excellent gas-sensing material but also shows great advantages in humidity sensing due to its porous structure and a large number of adsorption sites for moisture. The humidity-sensing mechanism is elucidated to reveal the reactions between graphene and water molecules, followed by the introduction of devices. Finally, the existing key challenges that hinder the further development and practical application of 3D graphene-based gas/humidity sensors are presented, followed by proposing the future perspectives.

Dopant-mediated surface charge imbalance for enhancing the performance of metal oxide chemiresistive gas sensors

“…58–61,66,75 This is probably due to the reason that the change in the electronic structure brought about by generating surface excess positive charges in an intrinsic n-type material needs extreme precision such that a stable electronic structure is sustained. The extension of the above studies into non-oxide-based gas sensors 78,79 is anticipated to establish a wider generality of the above correlations in a broad spectrum of chemiresistive gas sensing.…”

Emerging Materials for Water-Enabled Electricity Generation

“…WEG is emerging as a powerful technology for extracting energy from ambient water, with various operating types, remarkable performance, considerable conversion efficiency, and, most importantly, almost perfect environmental friendliness. For developing next-generation high-performance WEGs, the functional materials should also have the following characteristics: (i) excellent ionic conductivity and exceptional electronic insulation properties, which will facilitate the transport of ions, as the dynamics of ions plays a vital role in the electric generation process in WEGs; (ii) abundant chemical functional groups, which can tune the surface wettability, affect the surface charge density, facilitate adsorption of water, and give birth to mobile ions; (iii) robust mechanical frameworks, which are capable of handling the deformation of water-induced capillary force and external distortion, and maintaining the long-term stability for realistic applications; (iv) plentiful nanoporous structures, which are capable of promoting the uptake and evaporation of water, and advocating the transport of ions and water. In addition, the side reactions between materials and electrodes under both humid and dynamic conditions, should be evaluated and avoided as much as possible.…”

Recent Advances on 2D Materials towards 3D Printing

“…Most of the reported works for gas and humidity sensing are based on graphene due to its surface area, abundant reaction sites, and superior sensing performance [101,102]. However, black phosphorus has been used to respond to humidity, showing response to H 2 , O 2 , and CO 2 , and increased resistivity on exposure to NH 3 [103,104].…”