Enhanced electrochemical performance of MnO2 nanoparticles: graphene aerogels as conductive substrates and capacitance contributors

Abstract

An N-doped graphene aerogel (NGA) is used as a reactive container for growing MnO₂ nanoparticles via a soaking–hydrothermal strategy. MnO₂ nanoparticles pile up on the surface of reduced graphene oxide sheets with crosslinked structures serving as electrical conductors. Importantly, the NGA generates extra capacitance during the electrochemical process, which accomplishes a satisfactory compensation in the physical–chemical properties of MnO₂. As a cathodic electrode for Zn-ion batteries, the MnO₂/NGA exhibits a specific capacity of 275.8 mA h g⁻¹ and pre-eminent cycling stability with a retention of 93.6% at 3 A g⁻¹ after 1000 cycles. Meanwhile, the proposed electrode also shows a relatively high specific capacitance of 341 F g⁻¹ for a supercapacitor in 1 M Na₂SO₄. Meanwhile, the long-term cycling stability shows only a slight decrease by 5.1% of the initial capacitance after 5000 continuous cycles at 3 A g⁻¹, which indicates its superior electrochemical stability. Additionally, the assembled asymmetric supercapacitor also shows good electrochemical performance. This work highlights the extensive function of an N-doped graphene aerogel as a promising substrate for enhancing the electrochemical performance of MnO₂, which opens the gate for wide potential applications of graphene aerogel composites emphasizing their complementary effects.