Operating conditions of film capacitors are complex, and the problem of film insulation failure caused by repetitively pulsed voltage is becoming ever serious. Degradation of the film under repetitively pulsed voltage cannot be accurately evaluated by the average breakdown electric field. In this paper, the effects of pulsed electric field and pulse repetition frequency on the breakdown in biaxially oriented polypropylene (BOPP) films are investigated. Three phases of BOPP degradation are proposed based on the voltage amplitude, i.e., maintenance (M), decline (D), and near-zero (N). Evolution of the BOPP film from degradation to breakdown at different frequencies is presented. Meanwhile, transition of discharge mode and elemental composition of the film are analyzed. Experimental results show continuous heat generation under repetitive microsecond pulses is the dominant factor for degradation of BOPP film. The number of applied pulses and the repetitive stressing time decrease exponentially with increase of frequency. This research can be contributed to the safe and reliable operation of capacitors.

Sustainable ammonia synthesis at ambient conditions that relies on renewable sources of energy and feedstocks is globally sought to replace the Haber–Bosch process. Here, using nitrogen and water as raw materials, a nonthermal plasma catalysis approach is demonstrated as an effective power-to-chemicals conversion strategy for ammonia production. By sustaining a highly reactive environment, successful plasma-catalytic production of NH₃ was achieved from the dissociation of N₂ and H₂O under mild conditions. Plasma-induced vibrational excitation is found to decrease the N₂ and H₂O dissociation barriers, with the presence of matched catalysts in the nonthermal plasma discharge reactor contributing significantly to molecular dissociation on the catalyst surface. Density functional theory calculations for the activation energy barrier for the dissociation suggest that ruthenium catalysts supported on magnesium oxide exhibit superior performance over other catalysts in NH₃ production by lowering the activation energy for the dissociative adsorption of N₂ down to 1.07 eV. The highest production rate, 2.67 mmol g_cat.⁻¹ h⁻¹, was obtained using ruthenium catalyst supported on magnesium oxide. This work highlights the potential of nonthermal plasma catalysis for the activation of renewable sources to serve as a new platform for sustainable ammonia production.