The Preparation Of Transition Metal/n Doped Carbon Composites For Electrocatalytic Oxygen Reduction

Fuel cells and metal-air batteries are one of the ideal solutions for developing new green power supplies with high-performance.However,the oxygen reduction reaction at the cathode requires a catalyst due to the sluggish kinetics.Currently,the Pt/C catalyst of the battery cathode hinders the large-scale commercial application of batteries and metal-air batteries due to its high cost,intolerance to methanol and low stability.The non-noble metal based oxygen reduction catalyst is an ideal alternative to Pt/C catalyst due to its cost advantage and excellent catalytic effect of the oxygen reduction reaction.The morphology of most transition metal matrix composites are easy to control by using hard template method and their structure is stable in general.However,the process of the hard template method in the preparation of transition metal matrix composites is too cumbersome.Based on this,developing simple preparation and structure-controlling method have become the current exploration direction.In this paper,several transition metal composites are prepared and their electrochemical performance are studied.The main contents of this work are as follows:?1?Co@N-CNTs/rGO was prepared by pyrolysis method using graphite oxide as a template,urea as nitrogen source and cobalt acetate tetrahydrate as cobalt source.Co@N-CNTs/rGO has a three-dimensional structure in which graphene sheets and carbon nanotubes are interpenetrated,and metal cobalt nanoparticles are uniformly dispersed therein.Co@N-CNTs/rGO exhibits an oxygen reduction reaction catalytic performance?onset potential of 0.98 V?which is superior to commercial Pt/C catalysts in terms of catalytic activity,stability and methanol resistance.?2?Using melamine foam as nitrogen and carbon source,Co/CNTs-NC catalyst was obtained by high-temperature pyrolysis of melamine and cobalt salt.Co/CNTs-NC holds the three-dimensional structure in which carbon nanotubes and cobalt nanoparticles were evenly distributed on the carbon matrix.Electrochemical results demonstrate that the catalytic performance of the oxygen reduction reaction of Co/CNTs-NC was higher than that of NC.Co/CNTs-NC exhibits excellent oxygen reduction reaction catalytic activity,stability and methanol resistance.?3?FeCo@Co₄N/CNTs-NC is facilely prepared as an efficient oxygen reduction electrocatalyst for Al-air batteries via one-pot pyrolysis synthesis,and the homogeneous binary Co_0.7Fe_0.3 nanoalloy,Co₄N and in-situ derived carbon nanotubes grown on the carbon matrix are demonstrated.Owing to the synergistic effect of iron-cobalt alloy,Co₄N and carbon nanotubes,the catalyst exhibits remarkable catalytic activity with an onset potential of 0.98 V?RHE?in an alkaline solution,which is comparable to that of the commercial 20 wt%Pt/C.Moreover,the Al-air batteries based on the FeCo@Co₄N/CNTs-NC catalyst displays high discharge performance(the maximum power density of 167 mW cm^-2),which is close to that of commercial Pt/C.More importantly,the proposed synthesis approach is low cost,simple and easy to scale up.