The durability of proton exchange membrane fuel cells(PEMFCs)has been recently recognized as one of the key issues that have to be improved before the commercialization of PEMFC.To solve this problem,Wei and his colleagues have designed and synthesized a polyaniline(PANI)-decorated Pt/C@PANI core-shell catalyst that shows enhanced catalyst activity and durability compared with nondecorated Pt/C.In their invention,the aniline monomer was first selectively adsorbed on the surface of carbon via preferential π-π conjugation between the aniline and carbon support and then in-situ polymerized on the carbon surface by oxidation of ammonium peroxodisulphate in acidic solution.Unlike most of the Pt NPs being wrapped by PANI for Pt/PANI/C composite and cannot be utilized by fuel cell reaction,the PANI shell layer in the Pt/C@PANI core-shell catalyst is preferentially and selectively covered on the surface of carbon rather than Pt.The experimental results disclose that Pt/C@PANI demonstrates significantly improved stability compared with that of the unmodified Pt/C catalyst without sacrifice of activity.The high stability of the Pt/C@PANI catalyst is ascribed to its novel PANI-decorated core-shell structure,which induces both electron delocalization between the Pt d orbitals and the PANI π-conjugated ligand and electron transfer from Pt to PANI.The stable PANI shell also protects the carbon support from direct exposure to the corrosive environment.These results are significant with respect to the synthesis of highly stable Pt/C catalysts and the enhancement of ORR activity for fuel cell applications.We also develop a thiolated CNTs(SH-CNTs)by directly linking thiol groups on the CNTs surface for support of Pt nanoparticles.-SH groups on the surface of SH-CNTs serve as anchor centers for achieving high Pt dispersion.The DFT calculations indicate that the -SH group enhances the oxidation resistance of the Pt nanoparticles and CNTs and restricts Pt migration on the CNTs.DFT calculations suggest that the enhanced stability of Pt/SH-CNTs originates from the increased interaction between Pt and SH-CNTs and the depressed d-band center of the Pt NPs.Carbon,due to its chemical stability and electric conductivity,is widely used in an electrochemical system as conductive agent,catalyst supports and so on.However,carbon is not stable enough in the operation environment of fuel cells.It is subjected to corrosion of oxidative species,such as H 2 O 2,a common intermediate of the ORR.In addition,the poor interaction between carbon supports and metallic catalyst leads to metallic catalyst dissolution,Ostwald ripening and aggregation.Therefore searching more stable catalyst supports with acceptable electric conductivity is imperative for fuel cells commercialization.For the first time,we found that modified 2-D Ti3C2X2 nanosheets can substitute carbon for catalyst supports and give the supported Pt NPs catalyst an extraordinary stability.It seems we cannot find other more suitable catalyst supports for fuel cells than Ti3C2X2,containing excellent electric conductivity as good as carbon and much more chemically stable than carbon.