A three-dimensional MnO₂/graphene hybrid as a binder-free supercapacitor electrode

Highly aligned manganese dioxide (MnO₂) nanowall arrays electrodeposited onto Ti sheets are used as substrates to grow graphene (GR) through chemical vapor deposition (CVD), thus forming a three-dimensional (3D) MnO₂/GR hybrid composite. Furthermore, a 3D MnO₂/GR hybrid with different structures and properties has been prepared at different temperatures. The as-prepared hybrid materials could be directly used as supercapacitor electrodes without any binder and conductive additive, and fully maintain the high conductivity and high specific area of GR, and large pseudocapacitance of MnO₂ nanowall arrays. In aqueous electrolytes, the hybrids show a high specific capacitance of ∼326.33 F g^-1 with good cycling stability at the scan rate of 200 mV s^-1 and high energy density of 23.68 W h kg^-1 while maintaining high power density of 7270 W kg^-1. The preparation method provides a novel method to fabricate 3D graphene-based composite materials, and the as obtained hybrid electrode demonstrates its potential applications in supercapacitors.