Surface-Engineered 2D Nanomaterials in Gas Sensors: Advancement and Challenges.

2D nanomaterials like transition metal dichalcogenides (TMDs), MXene, nitrides, and black phosphorus-based gas sensors have garnered extensive attention in recent decades. The extra ordinary physicochemical and electrical properties of 2D nanomaterials make them highly sensitive toward gas molecules at room temperature. However, despite their potential, the current gas sensing technology suffers from inadequate selectivity, inaccurate detection and environmental instability. This review provides an overview of recent developments in surface-engineering routes to improve the sensing properties of 2D nanomaterials-based gas sensors. First, it covers emerging 2D nanomaterials, their synthesis routes, and gas-sensing mechanisms. Later on, thoroughly explores renowned surface-engineering strategies such as defect modulation, nanoparticle functionalization, and heteroatom doping to enhance the gas sensing performance. Metal intercalation and partial surface oxidation/reduction approaches are also discussed to tune the sensing characteristics. Furthermore, single-atom catalyst engineering highlights the anchoring of metal atoms on 2D nanomaterials to achieve enhanced atom utilization, leading to better catalytic sensing activities. The engineering techniques introduce effective surface sensitization, modulated carrier concentration in 2D materials. This review outlines the key objectives of surface-engineering strategies to overcome the limitations of hybrid materials and pave the way for next-generation sensors with enhanced sensing performance to impact a wide range of applications.