Controlled Preparation Of Pt-Based Nanostructures And Their Electrocatalytic Properties

With the increasing environmental problems and the rapid consumption of fossil fuels,people are committed to the development of green clean energy technology.Electrochemical water splitting and fuel cells are considered to be very promising new energy technologies because of their respective advantages.Platinum(Pt)is widely used in the above two types of reactions due to its excellent electrocatalytic properties.However,the low reserve,high price and the poor activity and stability in the catalytic process become the bottleneck restricting the development of Pt-based catalyst.In this paper,the controllable preparation of several carbon-supported monodisperse low-Pt nanocrystalline catalysts have been developed by controlling the growth conditions of Pt-based noble metal and monodisperse nanocrystals and nanocrystalline nucleation,growth thermodynamics and kinetics.The as-prepared catalysts show good catalytic activity and stability toward electrolytic hydrogen evolution reaction and fuel cell anode reaction.Specific research results and innovations are as follows:1.A facile and efficient strategy has been developed to synthesize a highly active and durable 3D Pt/C composite via the thermal decomposition of the coordination polymer.Under a flow of Ar/H2,the starting spherical precursor materials composed of Pt(?)organic complex polymers and tiny Pt nanoparticles(NPs)in the outer part,transforms into a uniform 3D Pt/C composite where monodisperse Pt NPs as small as?4.5 nm distributed homogeneously in the N-doped porous carbon.The diameter of the precursor spheres is nearly 30%larger than that of the annealed 3D Pt/C composite,demonstrating that an obvious shrinkage occurs during the annealing process.Meanwhile,the atomic ratio of N is 2.89%in the 3D Pt/C composite which can be attributed to pyridinic-N,pyrrolic-N,graphitic-N and oxidized-N,respectively.To investigate the effect of N-doped porous carbon in the electrocatalysis,the electrocatalytic activity and stability of the 3D Pt/C composite is accessed toward ethylene glycol oxidation reaction(EGOR),methanol oxidation reaction(MOR),and ethanol oxidation reaction(EOR)compared with the commercial Pt black catalyst.This strategy may open new avenues to the preparation of other highly active carbon-supported Pt-based bimetallic and multimetallic electrocatalysts.2.A moderate one-pot hydrothermal process has been developed to the preparation of NiPt nanocrystals with holothuria-like morphology.The self-assembly growthmechanism of the nanowires are investigated in depth.The holothuria-like alloyed NiPt nanowires are Ni-rich in composition and uniform in diameter with many tiny tips outstretched from the wires surface which are assembled from granular subunits with the assistance of capping molecular of ethanediamine.Actually,the as-grown NiPt nanowires where the atomic ratio of Ni and Pt is 23.6:1 firstly demonstrate high oxygen evolution reaction(OER)catalytic performance in 0.1 M KOH electrolyte and also display substantially high stability.In detail,The NiPt nanowires can afford a current density of 10 mA/cm2 at a relative small overpotential of 0.396 V and a Tafel slope of 55 mV/decade and it shows a quite small change of overpotential of?1.7 mV after 7000 s.The enhanced electrocatalytic performance may result from the changes in surface structure and faster electron transport due to the doping Pt.3.Based on the difference of redox potentials of the metals,a facile strategy has been estabilished to construct monodisperse CuPdPt nanocrystals via a simple galvanic replacement reaction in hydrothermal conditions.It is demonstrated that both Pd and Cu elements are homogeneously distributed throughout the nanocrystals and Pt is distributed partly at the exterior/outer surface of the nanocrystals.Then the nanocrystals are deposited on Ketjen carbon for the follow-up catalysis.Significantly,this CuPdPt/C hybrid composite exhibits superior eletrocatalytic activity and durability toward hydrogen evolution reaction(HER).The CuPdPt/C catalyst can achieve a factor of 701 enhancement in mass activity compared with the commercial Pt/C catalyst and it can endure at least 20000 cycles with negligible activity loss.More importantly,the total platinum content in the hybrid catalyst is merely about 0.095 wt%.4.A general synthetic method has been developed to the design of Pt-M(M = Ru,Ni,Co,Cu,Zn,Mn)bimetallic/intermetallic nanostructures where the acetylacetone compounds severd as the metal precursors.In especial,highly uniform,ultrathin worm-like polycrystalline PtRu nanowires with an average diameter of?1.8 nm have been directly fabricated and investigated in depth.The atomic ratio of Pt and Ni is 110.6:1,determined by ICP accurately.HRTEM.HADDE-STEM images and elemental mappings reveal that Pt element is distributed throughout the nanocrystals while Ru element was distributed scatteredly and there are plenty of defects around the boundaries/kinks/corners.The incorporation of trace highly efficient Ru can significantly result in the production of many oxygenated species,reacting with adsorbed poisonous intermediates on catalyst surface,releasing free the neighbouring Pt active sites simultaneously.Comprising the advantages of 1D worm-like nanostructures,the interaction between bimetallic Pt and Ru,the strong coupling between active components and the Kejen carbon support,the resulting PtRu nanowires/C hybrid composite showed much better electrocatalytic activity and CO tolerance compared with the commercial Pt/C(60 wt%Pt)catalyst for EGOR.