Enhancing Catalytic Performance Of Oxygen Reduction Reaction Catalysts Via Support Changing And Structure Controlling

Low temperature hydrogen oxygen fuel cells（FCs）are ideal candidate for mobile and stationary power generation due to their high-energy efficiency and environmentally benign process.Pt-containing materials（e.g.Pt/C）are currently the best electrocatalysts for FCs,however,their technological application in largescale is significantly hampered by scarcity,expensiveness,and poor electrochemical stability,and thus the development of high-performance and high-stable low-Pt or none-Pt catalysts has been the key issue for the commercialization of FCs.In recent years,on the one hand,the catalytic activity and stability of Pt catalysts have been improved by using new supporting materials,but further promotion of their overall performance is necessary.On the other hand,although studies of none-Pt catalysts have suggested that many less-cost materials can be used as replacement to Pt for FCs application,they are still less comparable to that of Pt-based catalysts especially when working under high current conditions.In this regard,we have carried out the following researches on the basis of the above mentioned object:（1）Enhancement in electrochemical stability of Pt catalyst by introduction of new supporting material.We show that the electrocatalytic performance of Pt can be largely enhanced by Pt-Ti strong interaction when Pt is supported on Ti,C-rich Ti₃C₂ nanosheets.The Ti₃C₂ nanosheets were prepared by extracting the Al layers from Ti₃AlC₂ using HF or KOH solution as leaching agent.The Pt/Ti₃C₂ catalyst exhibits improved activity and stability for the oxygen reduction reaction（ORR）compared with the Pt/C catalyst.The experimental results suggest that this significantly enhanced activity and stability of the Pt/Ti₃C₂ catalyst is a result of electronic structure changes of Pt nanoparticles upon their strong interaction with the Ti₃C₂ support compared to C.DFT calculations clarify why the Pt/Ti₃C₂ catalyst has excellent catalytic activity for the ORR in addition to keeping excellent stability.（2）High active and stable Pd catalyst.Pd has been widely investigated as effective Pt alternative because of its functional similarities to Pt.However,the electrocatalytic performance of Pd catalysts are still barely equivalent to those of typical Pt-containing materials in both acdic and alkaline media.We have developed an efficient strategy for the preparation of a novel Pd/rPOM hybrid catalyst demonstrating very high activity for the ORR compared to Pt/C and Pd/C catalysts in alkaline media.The in-situ-developed rPOM（reduced-polyoxometalate）support offers stable anchoring sites for the formation and subsequent attachment of Pd,enabling the full utilization of the catalyst surface by minimizing the agglomeration of Pd nanoparticles.Further investigations suggests that the ORR catalytic performance enhancement is a result of the changes in the electronic structure of Pd nanoparticles induced by synergistic interaction with the rPOM support,which weakens the interaction between Pd and nonreactive oxygen-containning species,providing more active sites for O₂ adsorption and activation.（3）Enhancement in kinetics of the oxygen reduction on a silver electrocatalyst by introduction of interlaced and defect-rich surfaces.We report an efficient rPOM-assisted route to synthesize novel nanoporous Ag（np-Ag）structure,a multigrain,whose surface is predominantly enclosed by interlaced facets and defect-enriched surfaces,for use as a catalyst for the ORR.Catalytic results show that the np-Ag material can electrocatalyze the ORR with activity close to that of Pt/C in alkaline electrolyte.The np-Ags’ excellent catalytic performance originates from the increased availability of surface/facet defects and the features of porous structure.Based on the experimental analysis,we provide an advanced viewpoint that could be used to further understand the catalytic performance of Ag nanomaterials from the electron density and structural defects points of view.