Defect-engineered two-dimensional layered gallium sulphide molecular gas sensors with ultrahigh selectivity and sensitivity

Detecting toxic gases, especially greenhouse gases, is one of the most challenging and complex tasks to maintain a sustainable environment. Based on first-principles theoritical calculations, we investigate the sensing performance of HCN, NH3 and SO2 gas molecules on GaS ML with and without Ga-/S-vacancy defects. The selectivity was investigated based on the electronic properties, charge transfer and adsorption energy of the most stable geometries of the adsorbed system. We predicted that HCN, NH3 and SO2 are physisorbed on GaS ML with and without Ga-/S-vacancy defects. The results show that Ga-/S-vacancy defective GaS ML exhibit stronger physisorption with HCN, NH3 and SO2 gas, which directly influences the sensing performance. The band structure and density of states indicate that electronic properties of Ga-/S-vacancy defective GaS ML have been altered upon gas molecules adsorption. We predicted ultrahigh selectivity with good recovery time for HCN, NH3 and SO2 gases on the defective GaS ML than pristine GaS ML. This suggests that vacancy defect is a highly active catalytic site to capture small gas molecules than pristine GaS ML. The theoretical findings suggest that Ga-/S-vacancy defective GaS ML can be used as a promising device for gas sensing applications and help guide experimentalists to develop better vacancy defective materials for efficient gas detection or sensing applications.