Hybrid Electrodes of Crosslinked Carbon Nanotube Networks and Their Electrocatalytic Performance

Author:Zeng Sha

Supervisor:li qing wen zuo jiang tao


Degree Year:2019





Zn-air battery with high specific energy density,excellent safety and environmental-friendly characteristics is one of the promising next-generation electrochemical storage devices.However,the performance is limited by the sluggish kinetic reactions in the air electrode.Developing high performance air electrodes with high catalytic activity,sufficient multi-phase catalytic interfaces,stable active sites and efficient mass or charge-transfer channels is the key issue in this research area.We explored the preparation of high-performance air electrodes based on highly conductive and crosslinked carbon nanotube(CNT)networks by developing means of the functionalization and heteroatom doping of the pristine networks,in-situ anchoring of metal based electrocatalysts on the networks,the construction of three-dimensional interconnected networks and the combination of photocatalysis with electrocatalysis.Herein,the results are mainly summarized in four aspects as follows.1.Electro-etching and anodic oxidization functionalization techniques were developed to overcome the hydrophobic nature and surface inertia of raw CNT networks.Oxygen reduction electrocatalytic performance and loading active sites of the functionalized CNT assemblies were enhanced meanwhile highly conductive porous networks were well-maintained.Two novel types of nitrogen modified CNT hybrid networks were synthesized via hydrothermal in-situ doping and electrothermal post-treatment doping methods.Improved oxygen reduction reaction catalytic activities with more efficient 4-electron processes were realized and they were comparable to commercial Pt/C catalyst or other nitrogen doped carbon nanomaterials catalyst with higher nitrogen contents.2.Through the replacement reaction of the residual Fe in CNT networks with Pt4+and the following transient Joule heating method,a hybrid film of homogenous PtFe alloy nanoparticles in-situ anchored on the functionalized CNT networks was designed.Atomic mixing of Pt and Fe resulted in shorter Pt-Pt bonds,which were more favorable for the desorption of oxygen.This well-alloyed structure and the stable anchoring of PtFe nanoparticles on CNTs were benefit to improve the utilization efficiency of Pt.The hybrid film with low Pt content(1.7 wt.%,6.8 μg cm-2)demonstrated much higher mass activity,stability and anti-poison property of methanol than the commercial 20 wt.%Pt/C catalyst.Furtherly,this recyclable self-supported hybrid film was directly applied on a fiber Zn-air battery with stable discharging performance and high rate performance,revealing the promising applications for the flexible and portable energy storage devices.3。A flexible bifunctional aerogel air electrode where non-precious cobalt oxide nanoparticles homogenously loaded on functionalized CNTs was developed,realizing the construction of three-dimensional,porous,and crosslinked networks.Oxygen-containing groups in the functional CNT networks provided anchoring sites for Co3O4 nanoparticles and attracted the introducing of nitrogen atoms.Benefiting from the synergistic effect of spinel cobalt oxide species and nitrogen doped CNTs,catalytic interfaces and active sites were greatly improved and the composite aerogel exhibits enhanced oxygen reduction and oxygen evolution catalytic performance.High performance all-in-one air electrode,combining the conducti ve current collector,catalyst and porous air diffusion electrode showed high bifunctional catalytic activity.All-solid-state film Zn-air battery exhibited low discharging/charging potential,excellent flexibility and stable cycle performance.4.A novel photo-responsive air electrode with TiO2 nano wires grown on CNT conductive networks via a simple hydrothermal reaction was developed.The combination of photocatalyst and electrocatalyst were benefit for the enhancement of oxygen reduction reaction and oxygen evolution reaction under light illumination.While this hybrid film was applied on the light-on condition,photo-induced electron or holes help the reduction of the overpotentials for both oxygen reduction reaction and oxygen evolution reaction.Also,the discharging/charging overpotential Zn-air battery utilizing this self-supported film as the cathode was slashed under light illumination.The proposed photo-assisted principle provides a new sight for the design of high-performance Zn-air battery.