Synthesis Of Pt-based Nanoalloy Catalysts And Their Applications In Electrocatalysis

Currently,Pt-based metal nanocrystals have been widely used in catalysis,electronics,sensing,and pharmaceuticals.In particular,Pt-based nanostructures have been widely developed in electrochemistry in recent years,such as liquid fuel cells,hydrogen evolution reaction(HER),and nitrogen fixation.The introduction of Pt-based catalysts can greatly reduce the energy barrier in the relative electrochemical reactions and simultaneously promote the transfer of electronic charges on the electrode surface.Thus,Pt-based nanostructures exhibit excellent electrocatalytic performance.However,the low abundance and high cost of Pthinder their large-scale commercial application.Therefore,the demand for high-performance noble metal catalysts is gradually changing to a clean and efficient catalyst that satisfies high catalytic performance while continuously reducing the use of noble metals and thus lowering the cost.Based on this,we achieve a significant improvement in the activity and stability of electrocatalysts by adjusting the composition,size and morphology of Pt-based alloy catalysts.The details of the work are sumerized as follows:1.The network PtCu nanocrystals(d<5 nm)formed by cross-linking from nanowires were synthesized by a one-pot method and PtCu catalysts exhibited excellent electrocatalytic performances for both N₂reduction reaction and methanol oxidation reaction at ambient conditions.A detailed investigation suggests that their electrocatalytic activity is highly composition dependent.We confirmed the production of NH₃from N₂through a systematic study.The optimum Pt₆Cu nanoalloys exhibit 2.3-fold and 20.6-fold increase in reduction activity toward NRR compared with pure Ptand Cu nanocrystals.Their faradaic efficiency values were also highly improved.Moreover,these bifunctional Pt₆Cu nanostructures also show excellent catalytic properties during methanol electrooxidation.The specific activity toward methanol oxidation reaches up to 21.3mA·cm^-2,which is 3.6 times that of commercial Pt/C catalysts.2.The PtM(M=Mn and Co)alloy nanofascicles were assembled by synthesizing ultrathin nanowires with a diameter of about 2.0 nm through a solvothermal reaction.Furthermore,the compositions of alloys were tunable.These nanofascicles exhibited significantly enhanced electrocatalytic activity due to their alloy nature,ultrathin size,and attractive morphological features.Noticeably,PtM electrocatalysts exhibited superior HER performances not only in the acidic but also in alkaline conditions when the electrocatalysts were deposited on a carbon paper.Pt₈Co nanostructures show the smallest?₁₀value of 26.1 mV under acidic conditions,which is significantly lower than that of Pt/C(63.4 mV).Under alkaline conditions,the?₁₀of Pt₈Co is 47.2 mV,which is substantially lower than that of commercial Pt/C(187.9 mV).Pt₆Mn shows the lower?₁₀values of 39.0 and 67.5 mV under both the acidic and alkaline conditions,respectively.In addition,PtM electrocatalysts exhibit excellent long-term durability under alkaline conditions.3.Two-dimensional ultrathin PtPdCu nanocrystals were prepared by surfactant-directed synthesis.The size and morphology of the resulting ternary alloy nanocrystals were precisely controlled by tuning the synthetic conditions.During the preparation,we introduced the octadecyltrimethylammonium bromide as a structure-directed template and surfactant to selectively synthesize two-dimensional nanostructures with the exposed(111)crystallographic planes.The shape of the PtPdCu nanocrystals vaired from nanodiscs(CNDs),nanotriangular plates(TNPs)to nanotriangular darts(TNBs)by changing the molar ratio of precursors Pt,Pdand Cu.The two-dimensional PtPdCu nanocrystals have excellent electrocatalytic performances for ethanol oxidation reaction(EOR)and methanol oxidation reaction(MOR)due to their unique two-dimensional nanostructures and trimetallic alloy synergistic features.Impressively,2D PtPdCu TNBs exhibit a higher mass activity of 4.24 A·mg _Pt^-1for EOR in comparison to the PtPd,PtCu,and pure Pt,which 4.87-folder of the commercial Pt/C(0.87 A·mg _Pt^-1).Moreover,PtPdCu TNPs and PtPdCu CNDs also exhibit a higher mass activity of 3.50 A·mg _Pt^-1and 2.48 A·mg _Pt^-1,respectively.For EOR,2D PtPdCu nanocatalysts also possessed the highest mass activity of 1.06 A·mg _Pt^-1,which was 4.07times than the commercial Pt/C.Moreover,the 2D PtPdCu shows the superor mass activity for ethylene glycol,isopropanol and glycerol electrooxidation,respectively.In addition,the PtPdCu electrocatalysts also show the excellent long-term durability and better CO anti-poisoning ability.