Phase evolution of perovskite LaNiO₃ nanofibers for supercapacitor application and p-type gas sensing properties of LaOCl-NiO composite nanofibers

This study reports the fabrication and characterization of LaOCl-NiO composite and LaNiO₃ nanofiber mats and their potential applications for p-type gas sensors and electrochemical capacitors. One-dimensional LaOCl-NiO composite and LaNiO₃ fibers were prepared via the electrospinning of LaNiO₃ precursor/poly(vinyl acetate) composite fibers followed by subsequent thermal annealing. The size and distribution of the primary particles within the LaOCl-NiO composite and LaNiO₃ fibers were largely governed by the calcination conditions (from 450 to 950 °C). The perovskite LaNiO₃ phase started to form at calcination temperatures that exceeded 750 °C. Upon the formation of the perovskite LaNiO₃ phase, the electrical resistivity decreased remarkably from 1.1 × 10 ⁶ to 0.692 cm. LaOCl-NiO composite fiber mats calcined at 550 °C and 650 °C showed p-type semiconducting gas sensing properties and exhibited significantly enhanced C₂H₅OH sensitivity against CO, H₂, NH₃ and NO₂ gases. The conducting LaNiO₃ fiber mats calcined at 750 °C were used as the basis of a hybrid electrochemical capacitor in which the fiber mats served as the conducting core for electrostatic spray-deposited manganese oxide overlayers. The manganese oxide/LaNiO₃ stacked electrodes exhibited a high specific capacitance of ∼160 F g^-1 at 10 mV s^-1.