Highly enhanced H2 gas sensing characteristics of Co:ZnO nanorods and its mechanism

We report here excellent H-2 gas response property of Co-doped ZnO nanorods (Co:ZnO NRs). Co:ZnO NRs have been synthesized by hydrothermal method by varying the Co content from 0 to 10 mol%. It is found that Co:ZnO NRs with 8 mol% of Co exhibits the highest and faster H-2 gas response ability compared to the undoped ZnO resulting in a 5 fold enhancement in the gas response in the presence of air at 150 degrees C. While the gas response value (S (%) = [(I-g-l(a))/l(a)] x 100, where la is the current of the sensors in the presence of air only and I-g is the current in the presence of certain H-2 concentration) to 3000 ppm H-2 for undoped ZnO NRs'sensor is 11%, an unprecedented high value of 53.7% is obtained for the Co:ZnO with 8 mol% of Co. Based on the electrical current and photoluminescence results, a mechanism for the enhanced H-2 response of Co:ZnO is proposed that involves donor-related oxygen vacancies (V-o) introduced by the Co dopants in the ZnO lattice. (C) 2016 Elsevier B.V. All rights reserved.