Preparation Of Air Cathode And Oxygen Reduction Performance Of CoNC Catalyst In MFC

Microbial full cells?MFC?can directly convert the chemical energy contained in organic matter in wastewater into electrical energy,and simultaneously realize energy recovery and sewage purification.It is a promising sustainable wastewater treatment and new energy technology.However,MFC currently has low power generation performance and high manufacturing cost,which limits its large-scale application in actu al sewage treatment.The poor performance of the electrocatalytic oxygen reduction?ORR?of air cathode catalyst and the high manufacturing cost are important factors that restrict the power generation efficiency and economic performance of MFC.The development of high efficiency and low cost cathode ORR catalyst is a difficult point in the current research of MFC.In this study,the zeolitic imidazole ester skeleton compound ZIF-67 was used as a self-success template,and a cobalt-nitrogen carbon?CoNC?catalyst was prepared by high-temperature pyrolysis.CoNC was combined with an inexpensive activated carbon catalyst to serve as an oxygen reduction catalyst for the air cathode,in order to improve the cathode ORR performance and reduce electrode preparation costs.In this paper two kinds of compound modes of CoNC and activated carbon are investigated:? Preparation of CoNC/metal mesh self-supporting air cathode.The ZIF-67 nanowires is grown on a metal mesh collector,and then CoNC catalyst was generated by high temperature pyrolysis,self-supporting air cathode was prepared by lamination with diffusion layer,finally the activated carbon is sprayed on the catalytic layer of CoNC/metal mesh self-supporting air cathode as common catalytic layer.?Preparation of CoNC-activated carbon co-doped air cathode.ZIF-67 was used as self-sacrificing template to prepare powder CoNC catalyst,which was doped with activated carbon in proportion to prepare a catalytic layer,and finally was pressed with metal mesh and diffusion layer to make air cathode.For the CoNC/metal mesh self-supporting air cathode,the important parameters of electrode preparation-collector type,diffusion layer type and ZIF-67 hydrothermal growth time were optimized,and the effect of activated carbon spraying on the self-supporting electrode ORR performance was investigated.The results show that the air cathode is prepared by the twill 60 mesh stainless steel mesh collector,the self-made carbon black diffusion layer and the hydrothermal 60 min condition.The cathode has the best ORR performance;the activated carbon is sprayed on the CoNC/metal mesh self-supporting air cathode catalytic layer.The ORR current of the air cathode at-0.3 V was increased by 875%.For the CoNC-activated carbon co-doped air cathode,the effects of CoNC and activated carbon doping ratio on the electrochemical performance of the air cathode and the MFC production performance were investigated.The results show that the doping amount of CoNC in activated carbon is increased from 0%to 20%,the ORR current density of air cathode is increased from 7.9 Am-2 to 14.1 Am-2,20%CoNC air cathode current density ratio sprayed activated carbon The CoNC/metal mesh self-supporting air cathode increased by 81%;jo increased from 0.2 to 0.75;the 20%CoNC air cathode had a MFC maximum power density of 1510.1 mW/m²,which was 31%higher than that of the undoped CoNC air cathode.CoNC has abundant catalytic activity sites,which can effectively improve the ORR catalytic performance of air cathode.NaH₂PO₂ was introduced into ZIF-67 to prepare different amount of CoNCP catalyst,and then air cathode was prepared by doping with activated carbon at a ratio of 20%.The PNP doping amount of CoNCP catalyst was increased from 500:5 to 500:50,500:20 CoNCP air cathode obtained the maximum ORR current density 17.1 A/m² and j0 value of 1.04×104 A/cm²,respectively,compared to 20%CoNC air cathode ORR current density and j0 values increased by 21%and 39%.The maximum power density of CoNCP air cathode is 2336.8 mW/m²,55%higher than 20%CoNC air cathode and 103%higher than activated carbon air cathode,respectively.The interaction between P atom and Co atom increases the defect site of CoNC catalyst,improves the conductivity and the ORR kinetic performance,making CoNCP catalyst have better ORR catalytic activity.