Studies On High Performance None-Pt Catalyst For Oxygen Reduction Reaction

Proton exchange membrane fuel cells(PEMFCs)have been used in many fields due to its high efficiency and low environmental impact.However,the commercialization of fuel cell system is limited by the development of cathodes catalyst.The insufficient electrocatalytic durability and the relatively high cost of catalysts still remains a major obstacle for large-scale commercialization of PEMFCs.Pt-based catalysts are the most efficient catalysts for the catalysis of the oxygen reduction reaction in fuel-cell cathodes,but it cannot meet the demands for fuel cells because of the high price of platinum.The development of high-performance and low-cost catalytic non-platinum materials for the oxygen reduction reaction has been the key point for the large-scale application of fuel cell.Based on this situation,we have carried out the following research.(1)Polyoxometalalte(POM)display the underlying application value in electro-catalysis which owe to the adjustable multi-functional structures and reversible redox property.We first used POM as precursor and NaBH4 as reductant to synthesis reduced-polyoxometalate(rPOM),then Na+ attach rPOM via electrostatic attraction to obtain the Na-rPOM catalyst.The as-prepared rPOM exhibits unsaturated Mo species,which are important to maximize the interaction between rPOM cluster and the counter Na+ ions.XRD,XPS and FTIR measurements were carried out on the samples to probe the compositions.According to the results,although the NaBH4 reduction of POM induces modification in the clusters’ structure,it does not induced decomposing in the clusters’ structural arrangements.SEM images reveal that the Na-rPOM exhibit a porous network consisiting of disordered nanoarchitecture.According to BET method,total pore volume of Na-rPOM is 102 m2 g-1,which is 9.2 times higher than pristine POM.The accelerated durability test(ADT)shows that Na-rPOM only about 22.61% decrease in current after tested for 10,000 s.(2)Palladium has been considered as an ideal candidate for Pt-based catalysts,thus,we successfully used PdCl2 as precursor and reduced polyoxometalate as reductant to synthesize nanoporous Pd catalyst(np-Pd).(311)(220)(222)facets are found in the TEM images of the np-Pd catalyst.These complex surface structure may help improve the ORR activity.XPS shows that the 3d binding energy of Pd in np-Pd(3)shift positively when compared with commercial Pd/C,which reveals that Pd-O bond strength is decreased.The ORR half-wave potential is 0.903 V,23mV positive shift compared with Pt/C.The mass and specific activity of prepared np-Pd catalysts are nearly 2.8 and 3.5 times higher than the commercial Pt/C catalysts.The accelerated durability test shows that the np-Pd catalysts only decreased 23.55% in electrochemical surface area(ECSA),whereas the commercial Pt/C catalysts have lost 45.00% of their initial ECSA after 2000 CV.