Fusarium oxysporum mediated synthesis of nitrogen-doped carbon supported platinum nanoparticles for supercapacitor device and dielectric applications

Abstract

A scalable method has been developed for synthesizing nitrogen-doped carbon-supported platinum nanoparticles. Fusarium oxysporum was utilized as reducing and stabilizing agent, and calcination was employed to produce the carbon support. The unique properties of Fusarium oxysporum facilitate the reduction of metal ions while preventing agglomeration and maintaining nanoparticle stability. An extensive investigation of the electrochemical supercapacitor and temperature-dependent dielectric properties of the nanoparticles demonstrates their suitability for supercapacitor applications. Electrochemical analysis showed N-doped C/Pt NPs with high specific capacitance, 482.77F/g at 2.0 A/g, retaining 94 % capacitance even under 20 A/g after 10,000 cycles. The symmetric supercapacitor device displayed 275F/g at 2 A/g, maintaining 61.10 Wh/kg energy density at 1000 W/kg power density, with ∼ 92 % capacitance retention after 10,000 cycles. Dielectric properties of N-doped C/Pt NPs were analyzed at both ambient (300 K) and elevated (450 K) temperatures, revealing temperature-dependent characteristics and alternating current conductivity. At 0.75 MHz, the dielectric permittivity (ɛ’) was measured at 31, with tangent loss at 2.01 and a.c. conductivity at 2.597 × 10^-3 O−1 m⁻¹. Increasing the frequency to 6.0 MHz resulted in a 2.38-fold rise in dielectric permittivity and a decrease in tangent loss to 0.77, demonstrating the temperature-sensitive nature of dielectric relaxation.