Green synthesis of ultrafine Methyl-cellulose-derived porous carbon/MnO2 nanowires for asymmetric supercapacitors and flexible pattern stamping

Abstract

A green and scaled-up strategy has been successfully employed to fabricate asymmetric supercapacitors (ASC) in conjunction with high energy density as well as highly efficient electrode materials. In this study, a B, N-dual doped porous carbon aerogel negative and a novel ultrafine nanowire positive composite, composed of manganese oxide (MnO2) core and carbon aerogel shell, were proposed. Methyl cellulose (MC) is spaciously available and the affluent hydroxyl groups on the molecular chains are conductive to trigger supramolecular assemble process to form self-crosslinking hydrogel. And then the hydrogel was dried and carbonized to obtain the B, N-dual doped porous carbon aerogel (BN-MC), with the specific area of 989.8 m2 g−1. Subsequently, a facile and efficient hydrothermal system, introduced to synthesize BN-MC/α-MnO2 composite, is prone to achieve hybrid nanowires with an average width of ∼15 nm. The prepared 0.1BN-MC/MnO2-8 sample (0.1 M NH4HB4O7 doping agent and 8 mg BN-MC addition) exhibits highest electrochemical behavior, whose capacitance is up to 338 F g−1 at 1 A g−1. That is ascribed to the well-dispersed α-MnO2 nanowires and uniformly cladding BN-MC shell. The ASC, assembled with BN-MC/MnO2 and BN-MC, significantly enhances energy density reaching to 27.75 Wh kg−1 at a power density of 1.35 kW kg−1 operating under 1.8 V voltage window. This ASC also shows superior cycling stability for maintaining 95.6% initial capacitance after 2000 cycles. What’s more, the BN-MC/MnO2 can be stamped into arbitrary patterns in seconds. This provides a new rapid prototyping technology for fabricating flexible and portable micro-supercapacitor devices.