Fabrication And Application Of The High Efficiency Nano-Au Catalyst For Oxygen Reduction

Developing green and renewable energy technologies to mitigate our reliance on fossil fuels has been attracting a great deal of interest in the past decade.Proton exchange membrane fuel cell?PEMFC?is a promising alternative energy resource thanks to its merits such as mild working temperature,high specific energy,fast start-up speed,and so on.However,there are several problems that hinder the commercialization of fuel cells,and solving these problems depends on the catalysts and advanced electrochemical technology.Developing high-efficiency electrocatalysts for oxygen reduction reaction?ORR?occurring at the cathode is crucial for large scale commercialization of PEMFCs.Nano-Au materials including Au clusters with ultrasmall size,Au nanoparticles with relatively larger size as well as Au based alloys,have attracted widespread attentions as efficient catalysts for ORR recently.This thesis will mainly introduce the fabrication and application of the high efficiency Nano-Au catalyst for oxygen reduction,which was synthesized by an environmental friendly and straightforward method.The relationships between the structure and function were studied by means of the characterization tools and electrochemical tests.The main contents are as follows:?1?Molecular Au₁₀₂?p-MBA?₄₄ clusters were loaded on the porous carbon nanosheets?AuCNS?employed as highly efficient electrocatalysts for ORR,which were fabricated by a wet chemical and physical mechanical method.The results showed that the AuCNs are effective ORR catalyst in 0.1 mol L^-1 KOH,with an onset potential of+0.96 V vs.RHE,low H₂O₂ yields?<20%in the low overpotential range of+0.50 to+0.80 V?and superior stability than Pt/C.According to the electrochemical test and structural characterization results,the sample with a 30%Au mass loading was identified as the best catalyst among the series,with a performance comparable to that of commercial Pt/C.The results elucidate that,through an effective approach,high-performance ORR catalysts based on Au nanoclusters supported on carbon nanosheets can be achieved;?2?By employing peptide R5 with the sequence of SSKKSGSYSGSKGSKRRIL as the template,Au and Pt nanomaterials were fabricated by an efficient wet chemical method,then were employed as catalyst for ORR.The results show that their structure and ORR catalytic activity can be optimized by tuning the metal-to-peptide ratio.Spherical nanoparticles were obtained for both Au and Pt in lower metal-to-peptide ratios,while higher metal-to-peptide ratio led to the formation of nanoribbons and/or networked nanochains.These Au or Pt nanomaterials with different shape demonstrated distinctively different ORR activity.The findings can shed light on rational design of peptide templated noble metal nanomaterials with desired structural control and optimized electrochemical properties as catalyst in electrochemical reactions;?3?Employing peptide A4 with the sequence of NPSSLFRYLPSDAG as template,stable AuAg alloyed nanoparticle networks were fabricated by efficient wet chemical method.Interestingly,well-defined sphericalparticles were obtained when only Ag or Au existed alone with A4.The series of A4-AuAg nanomaterials with different shape display effectient ORR catalytic performance.The catalytic performance can be tuned and optimized by changing the Au/Ag ratio.According to the electrochemical test and structural characterization analysis,the sample with the Au:Ag:A4 ratio of 10:30:1 displayed the best ORR performance among the series samples.It can be accounted for the protection of peptide A4 that can prevent the aggregation of metals,and the synergistic effects between Au and Ag.