Executive Summary : | Hydrogen gas holds boundless potential for becoming an alternative clean energy fuel. However, hydrogen reacts violently when it encounters chlorine, oxygen, or other oxidizers, thus making its rapid sensing (below 4%) very important for its widespread use. Currently, hydrogen sensors (optical, electrochemical, and thermoelectrical) suffer from issues like, long response/recovery times and the requirement of sophisticated instruments. Chemiresistive gas sensors are operated by a change in electrical resistance following the surface reactions or adsorptions of target gases. This class of sensing technology is quite promising because of simple instrumentation, rapid analysis and low cost.
Conducting crystalline porous frameworks with tunable pore surface and high dispersion of components are one of the most ideal sensing materials since chemical sensing properties are mainly influenced by surface reactions. The project aims at designing of efficient metal organic frameworks(MOFs) and Covalent organic frameworks(COFs) based chemiresistive hydrogen gas sensors(yet to be developed in literature) by achieving ultra-high dispersion of noble metals(Pd, Pt, Rh and Ir) on the interior surfaces of the frameworks. Here we target to achieve close to atomic dispersion(much less than 1 nm) of noble metals on the framework. Here the rationale is that hydrogen can be readily dissociated into hydrogen atoms over atomically dispersed noble metals then spillover to the redox active surface of crystalline framework thus resulting a change in the resistance. Here we plan to use redox linkers of conducting MOFs/COFs as anchoring sites for noble metals. The adsorption of metal on organic ligand can lead to metal-ligand charge transfer thereby altering the overall electronic structure of the MOF/COF, which will dictate the gas sensing ability of these systems. The feasibility of proposed new methodology for the single atom dispersion is supported by the synthesis of close to atomically dispersed Pd over redox active CrCl2(pyrazine)2 MOF.
To gain in-depth understanding of hydrogen interaction with sensing element (metal decorated crystalline frameworks), we will measure hydrogen isotherms,hydrogen chemisorption, as well as pressure-composition isotherms. Further we will be performing DFT calculations to study the various linker-metal interactions which will provide an understanding of binding energies and its stability.
To facilitate the processability of the designed materials, we propose to exfoliate bulk 2D MOFs/COFs into 2D few-layer sheets(resemble structurally with graphenes) using “solvent-assisted exfoliation” method for the fabrication of thin films. The gas sensing measurements will be carried out over home-built gas sensing station comprising of a source meter and probe station.
Overall, the project deals with the development of efficient hydrogen chemiresistors that uses single atom decorated conducting crystalline frameworks as sensing element. |
Co-PI: | Prof. Keloth Basavaiah Andhra University,Andhra University, Waltair Junction,Andhra Pradesh,Visakhapatnam-530003, Dr. Rajamani Raghunathan Ugc-Dae Consortium For Scientific Research,University Campus, Khandwa Road,Madhya Pradesh,Indore-452001 |