Modification Of Negative Electrode Materials For All Vanadium Redox Flow Batteries

Large scale energy storage combined with renewable energy sources such as solar,wind and tidal energy attracted more and more attention these years.VRFB been proved to be one of the most promising energy storage system due to the low cost,long cycle life,deep-discharge capability,flexible design and rapid respond timeRecently,the basic research of VRFB made great progress,but its industrial application is still in the bottleneck period.The stability,catalytic activity and the cost of the electrode materials are key factors to determine the development of VRFB industrialization.Many great works on VRFB electrodes mainly focus on the positive side,but negative electrode activity can't be ignored.Therefore,it's essential to find excellent materials for negative electrode.In this paper,carbon nanotube coated lead,bismuth species composite catalyst were prepared by an impregnation-calcination method,introduction of catalyst on the hydrogen evolution reaction and the electrocatalytic activity on the cathodic reaction of VRFB were investigated by quasi-steady-state polarization curve,cyclic voltammetry and electrochemical impedance spectroscopy.In the third chapter,the lead monoxide modified Carbon nanotubes composite(PbO/CNTs)was prepared by an impregnation-reduction method.The effects of the introduction of Pb species on the hydrogen evolution reaction and the electrocatalytic activity on the cathodic reaction of VRFB were investigated by quasi-steady-state polarization curve,cyclic voltammetry and electrochemical impedance spectroscopy.And the charge-discharge performance of the VRFB using PbO/CNTs as the electrocatalyst of negative electrode was evaluated by a galvano-static charge-discharge method.The experimental results show that the PbO/CNTs composite can effectively inhibit the hydrogen evolution reaction(HER)with negative shift of HER potential from-0.9628 V to-1.1490 V under 1 A·cm-2 after the introduction of Pb species onto CNTs.And the PbO/CNTs composite shows better electrocatalytic activity on the negative reaction of VRFB when compared with CNTs.In addition,the charge-discharge capacities of the VRFB using PbO/CNTs modified carbon felt as negative electrode are ca.100-200 mAh higher than that using CNTs modified carbon felt as negative electrode;and better capacity stability during the charge-discharge cycles can be observed as well.In the fourth chapter,the bismuth modified Carbon nanotubes composite(Bi/CNTs)was prepared by an impregnation-calcination method.The effects of the introduction of Bi nanoparticles on the hydrogen evolution reaction and the electrocatalytic activity on the cathodic reaction of VRFB were investigated by quasi-steady-state polarization curve,cyclic voltammetry and electrochemical impedance spectroscopy.And the charge-discharge performance of the VRFB using Bi/CNTs as the electrocatalyst of negative electrode was evaluated by a galvano-static charge-discharge method.Compared with the PbO/CNTs,Bi/CNTs own similar potential of hydrogen evolution,but its electrocatalytic activity is better.In addition,the initial charge-discharge capacities of the VRFB using Bi/CNTs modified carbon felt as negative electrode are ca.100 mAh higher than that using CNTs modified carbon felt as negative electrode;50 weeks after the VRFB capacity just for little attenuation,the stability of electrode turns better.In the fifth chapter,the Bi and PbO modified Carbon nanotubes composite(PbO/Bi/CNTs)was prepared by an impregnation-calcination method.The effects of the Pb spacies and Bi nanoparticles on the hydrogen evolution reaction and the electrocatalytic activity on the cathodic reaction of VRFB were investigated by quasi-steady-state polarization curve,cyclic voltammetry and electrochemical impedance spectroscopy.And the charge-discharge performance of the VRFB using Bi/CNTs as the electrocatalyst of negative electrode was evaluated by a galvano-static charge-discharge method.The experimental results show that the PbO/Bi/CNTs composite can effectively inhibit the hydrogen evolution reaction(HER)with negative shift of HER potential from-0.9628 V to-1.081 V under 1 A·cm-2 after the introduction of Pb spacies and Bi nanoparticles onto CNTs;And the PbO/Bi/CNTs composite shows the better electrocatalytic activity on the negative reaction of VRFB when compared with CNTs.In addition,PbO/Bi/CNTs as negative catalyst of VRFB.the charge and discharge capacities of were higher than the other three kinds of electrodes,while hydrogen evolution potential decline slightly when Pb and Bi exist at the same time,but the electrodecatalytic been improved.From the competitive mechanism of the reaction kinetics,the hydrogen evolution reaction been inhibited,indicate that PbO/Bi/CNTs can be as good catalyst on VRFB.