Microwave hydrothermal synthesis of nanoporous cobalt oxides and their gas sensing properties

Abstract In this paper, the precursors were synthesized by microwave hydrothermal method using Co(NO 3 ) 2 ·6H 2 O as raw material, CO(NH 2 ) 2 and KOH as precipitants, respectively. The precursors and calcined products were characterized by XRD, FESEM, and BET–BJH. The results show that both constituent and synthetic condition can determine the products morphology. When using KOH as precipitant, hollow Co 3 O 4 nanorings were obtained whose precursor was synthesized at 140 °C for 3 h and calcined at 500 °C in air for 2 h. While using CO(NH) 2 , Co 3 O 4 like-nanochains were obtained whose precursor was synthesized at 110 °C for 1 h and calcined at 420 °C in air for 2 h, and Co 3 O 4 nanosheets were obtained while their precursor was synthesized at 140 °C for 3 h and calcined at 500 °C in air for 2 h. The sensitivity test of Co 3 O 4 to alcohol reveals that the hollow Co 3 O 4 nanorings show the best sensitivity, porous Co 3 O 4 like-nanochains are superior to that of the porous nanosheets.