Constructing Sn0.92In0.08O2–In2O3 heterostructure via the dual synergy for improving CO sensitivity

Abstract

Improving the CO sensitivity for SnO2-based gas sensors has always been worthy of attention. Herein, we put forward a novel thought to enhance CO sensing performance via taking advantages of the large specific surface area of Sn0.92In0.08O2 (SI0.08O, x = 0.08) by doping modification and the heterojunction effect by combining SI0.08O with In2O3 to construct n-n heterostructure. For better distinguishing the respective contributions of In3+ doping and heterostructure construction on improving sensing performance of pristine SnO2 towards CO, SIxO (x = 0.01, 0.03, 0.05, 0.08 and 0.10) were firstly tested to determine the optimum In3+ doping concentration, then SI0.08O–In2O3 nanocomposites (SI0.08O-xINO, x = 20, 30, 40 and 50, which indicates respectively the mole percentage of In3+ in Sn4+ and In3+) were successfully prepared by grinding-annealing methods and the effect of In2O3 content on CO sensitivity was investigated. Among these materials, a superior gas sensitivity of SI0.08O–40INO was realized with the response value of 15.2 towards 3000 ppm CO, which was over 1.5 times that of SI0.08O, and the response time was 18s. Besides, by tuning the In2O3 content in SI0.08O-xINO, the selectivity towards CO could increase up to 5 times that of pristine SnO2. The improved gas sensing performance of SI0.08O–40INO was mainly ascribed to the large specific surface area, the successful construction of electronic transmission channel, the formation of abundant number of SI0.08O–In2O3 heterojunctions and the high grain boundary barrier at the interface between SI0.08O and In2O3. This work also realized the quantitative regulation of the ratio relationship between the In3+-doped SnO2 and In2O3 in binary heterostructured nanocomposites.