Nitrogen-rich Nanoporous Carbon Materials For Oxygen Reduction Reaction

Traditional fossil fuels face enormous challenges due to resource shortage and environmental pollution issues.The worldwide increasing demand for clean energy has directed the research efforts towards alternative and efficient energy conversion technologies.Fuel cell is considered as one of the most promising energy conversion technologies because of its high energy conversion efficiency,environmental friendliness,and high reliability.However,the key to the development and application of fuel cell is to overcome the slow kinetics of cathodic oxygen reduction reaction?ORR?.It is currently recognized that the most catalytically active catalysts are platinum?Pt?and platinum-based materials,but they are inhibited for commercial applications due to their high cost,low reserves and poor durability.Therefore,it is urgent to find and develop inexpensive,highly active,and stable electrocatalyst to accelerate the commercialization of fuel cells applications.In this paper,acrylamide monomer was added to graphene oxide?GO?aqueous solution or commercial PAM was added to form composite hydrogel,and then MOF derived carbon material was added.After high-temperature carbonization and acid etching process,cheap and highly active non-noble metal oxygen reduction catalyst can be synthesized.First,acrylamide?AM?,MIL-100?Fe?and graphene oxide were used as raw materials to prepare a non-precious metal catalyst for effective oxygen reduction reaction.The effects of addition of MIL-100?Fe?and carbonization temperature on the oxygen reduction performance of catalysts were investigated in detail.Among them,when the carbonization temperature is 800^°C and the mass fraction of MIL-100?Fe?is 30%?m=0.3?,the catalyst PAM/0.3MIL-100?Fe?/GO-800 has the best ORR performance in 0.1 M KOH.The performance has an initial potential of0.901 V?vs.RHE?,an oxygen reduction peak of 0.74 V,and a limiting current density of 4.86 mA cm^-2.The initial potential of Pt/C was 0.902 V?vs.RHE?,the peak of oxygen reduction was 0.79 V,and the limiting current density was 5.02 mA cm^-2.Comparing the ORR performance of PAM/0.3MIL-100?Fe?/GO-800 and Pt/C,it can be seen that the ORR performance of the two is comparable,but the cost of Pt/C is higher.Therefore,PAM/0.3MIL-100?Fe?/GO-800 can be used as an inexpensive oxygen reduction catalyst with good ORR performance and long-term stability to replace Pt/C.Nitrogen-doped carbon with well-dispersed and three-dimensional porous network structure has been fabricated for efficient oxygen reduction reactions by using polyacrylamide?PAM?and zeolitic-imidazolate-framework?ZIF?and graphene oxide as raw materials.The PAM is favor for the formation of three-dimensional porous structures,while the ZIF inhibit the agglomeration of the derived carbon during high temperature annealing.Among them,PAM0.6/Zn-ZIF/GO-800 calcinated at 800^°C with a PAM concentration of 60%?x=0.6?shows the largest specific surface area?1,458 m²/g?and best ORR performance in 0.1 M KOH,which gives an onset potential of 0.918 V?vs.RHE?,which is even more positive than Pt/C?0.902 V vs.RHE?,demonstrating its superior ORR capability.The ORR performance can be further improved by involving cobalt into the composite?denoted PAM0.6/Co-ZIF/GO-800?,which can be prepared by using cobalt nitrate as a metal source.As an ORR catalyst,it exhibits a more positive onset potential?0.935 V vs.RHE?than PAM0.6/Zn-ZIF/GO-800?0.918 V vs.RHE?.The good ORR performance together with its long-term stability and better methanol tolerance make it a promising non-noble catalyst for fuel cell applications.