Synthesis Of Mn-Co Spinel Composite Oxygen Reduction Electrocatalyst And Its Application In Alkaline Membrane Fuel Cells

As an ideal energy source,hydrogen is expected to replace traditional fossil fuels and significantly reduce carbon dioxide emissions.In the process of applying hydrogen energy,using fuel cells to directly convert chemical energy stored in hydrogen energy into electrical energy is an ideal way.The oxygen reduction reaction（ORR）at the cathode of a fuel cell is a key step.Compared to the severe corrosion of catalysts in acidic media and the dependence of precious metal catalysts in proton exchange membrane fuel cells（PEMFC）,alkaline membrane fuel cells（AEMFC）can use non precious metal catalysts,which may have cost advantages.Developing high-performance and low-cost non noble metal alkaline ORR electrocatalysts is of great significance for the commercialization of AEMFC.In this paper,we designed and synthesized a composite catalyst of spinel nanoparticles and doped carbon based materials to improve the activity of ORR electrocatalyst,optimize the water management of the fuel cell catalytic layer.Then obtain the improvement of AEMFC performance.The main research results obtained include the following two aspects:（1）Spinel type oxide Mn Co₂O₄was prepared by hydrothermal method,and the regulation of its ORR activity through doping,recombination,and other methods was explored.The results indicate that the composite of Mn Co₂O₄and single atom carbon based materials can effectively enhance its ORR catalytic activity.The prepared Fe NC supported Mn Co₂O₄catalyst（Mn Co₂O₄/Fe NC）exhibited good ORR catalytic activity,with an ORR half wave potential of 0.86 V in 0.1 M KOH.The improvement in activity is attributed to the higher specific surface area,better conductivity,and catalytic promotion of single atom carbon based supports for ORR.The AEMFC membrane electrode prepared using Mn Co₂O₄/Fe NC as the cathode exhibits higher performance than the membrane electrode prepared solely using Mn Co₂O₄or Fe NC,with a peak power of 1340 m W cm^-2.The synergistic effect of Mn Co₂O₄and single atom carbon based material Fe NC can effectively improve the performance of AEMFC.The analysis shows that,in addition to the enhancement of ORR intrinsic activity caused by the use of Fe NC as a support,Fe NC is more hydrophilic than commercial carbon black,which is conducive to optimizing AEMFC water management and improving AEMFC performance.（2）Further regulate single atom carbon based supports to improve the performance of AEMFC membrane electrodes.Further S-doped of Fe NC support to synthesize Fe SNC and use it to support Mn Co₂O₄spinel to prepare Mn Co₂O₄/Fe SNC catalyst.Its ORR half wave potential increased to 0.87 V in0.1 M KOH.However,because Mn Co₂O₄/Fe SNC catalyst is too hydrophilic,AEMFC prepared with Mn Co₂O₄/Fe SNC catalyst has serious water management problems,resulting in poor battery performance.To address this issue,Vulcan carbon black was added as an additive in the catalytic layer to construct a Mn Co₂O₄/Fe SNC/C composite catalytic electrode,solving the problem of the Mn Co₂O₄/Fe SNC catalytic layer being too hydrophilic,improving its mass transfer performance under high current conditions,and achieving an improvement in AEMFC performance.Further systematic optimization was carried out on the carbon content in the Mn Co₂O₄/Fe SNC/C catalytic layer,resulting in a high-performance Mn Co₂O₄/Fe SNC/C composite cathode catalytic layer film electrode with a peak power density of 1559 m W cm^-2(at this point,current density is 3480 m A cm^-2).This provides a beneficial exploration for the large-scale commercial application of AEMFC.