Synergistic Potential of MIL-101(Cr) and Reduced Graphene Oxide (rGO) in Designing High-Performance Ammonia Sensors

Abstract

The confluence of metal-organic frameworks (MOFs) and conductive materials has revolutionized gas sensing technology. This study presents a synergistic composite of MIL-101(Cr) and reduced graphene oxide (rGO) for enhanced ammonia gas sensing. The rGO-MIL-101(Cr) with varying the percentage of MIL-101(Cr) were synthesized and further characterised with various techniques. By harnessing the exceptional surface area and tailored pore structure of MIL-101(Cr) in tandem with the superior conductivity of rGO, the composite exhibits remarkable sensitivity and expedited response times. Among the prepared compositions, 20 wt.% rGO-MIL-101 (Cr) has demonstrated exceptional sensitivity towards ammonia detection, with sensitivity of -18.87 for 60,000 ppm and -5.24% for 2,000 ppm of ammonia gas and a discernible response at concentrations as low as 1 ppm. Notably, the composite's response remained remarkably consistent and stable, even after one year. This outstanding durability and stability underscore the composite's potential for reliable and long-term ammonia sensing applications. At this percentage, highest sensitivity is due to the perfect coordination bonding between ammonia molecules and the chromium nodes in MIL-101(Cr), modulating its electrical properties. The formation of perfect interface between MIL-101 (Cr) and rGO facilitates the efficient charge transport, thereby enabling precise detection of ammonia gas. The FE-SEM and TEM analysis clearly shows the presence of this kind of interface. Notwithstanding the comparable or superior sensing capabilities of existing ammonia sensors under optimal conditions, their practical utility is frequently compromised by the susceptibility of the constituent materials to humidity. In contrast, our rGO-MIL-101(Cr) composite exhibits a unique synergy of outstanding sensing performance and notable stability in moist conditions, due to its remarkably high surface area and durable architecture. This exclusive combination of properties enables our material to surpass the performance of existing sensors in real-world settings, where moisture is a common factor, and thus offers a significant advantage over existing sensors. This research highlights the potential of MOF-based composites for advanced gas sensing applications, paving the way for further exploration and development of novel sensing platforms.