The Synthesis Of Composite Materials Between Noble Metal Nanocrvstal And Two-dimensional Materials And Their Application On Electrocatalysis

The overuse of fossil fuel has brought a tremendous development to human society,endowing human the power of nature remodeling.However,serious energy and environment crises threaten the survival of mankind.Researchers from the whole world were urged to search clean and renewable alternative energy source by continuous global warming and energy issues from 20th century.Hydrogen arguably is the ultimate energy for humanity,which has the highest calorific value,clean combustion products and rich source.On the other hand,fuel cell is the most effective device for utilization of hydrogen to convert the chemical energy in hydrogen into electric power directly.Fuel cell possesses many advantages,such as high energy density,efficient electricity generating and zero carbon emission,and is promising in transportation,distributed power generation and portable mobile power supply.However,the development of hydrogen energy industry is hindered by the lack of methods to produce hydrogen in large-scale cleanly and low performance of fuel cell.More importantly,the performance of catalyst needs to be improved substantially.Noble metal nanocrystals are utilized in various field in modern industry because of their excellent catalytic activity and stability.But the high price and scarce reserve limit the extensive use of noble metal.In this respect,researches of many countries have done a lot of efforts on improving the catalytic performance of noble metal nanocrystal by regulating the structure,composition,morphology and supported materials.However,the performances of these catalysts are still not satisfactory and there is great room for improvement in catalytic activity and stability.In this dissertation,we have developed several facile methods to synthesizing the composites consisting of noble metal nanocrystals and two-dimensional materials.The controllable synthesis of graphene and MXenes supported nanoplates and nanowires as well as their catalytic performance are thorough researched.The main innovative results are as follows:(1)We have developed a facile method to synthesize single-crystalline PdSP encased within {100} facets using GO as the template.The key to the formation of the PdSP is the use of GO with the carbonyl group produced by thermal annealing at an appropriate temperature.The introduction of Br-ions derived from KBr is responsible for the formation of{100}facets exposed on the surface of the Pd nanoplates through selective adsorption.The {100} PdSP@rGO exhibits a superior catalytic performance for the FAOR because of the facet effect and large ECSA arising from the 2D structure.(2)We have developed a facile method to synthesize PdAu nanoplates on rGO with different core-shell structures.The key to the success of this synthesis is to control the injection rate of Au precursor solution with an aim to tune the galvanic replacement and co-reduction in the presence of Br-ions and AA.Core-shell and alloy integrating PdAu nanoplate exhibits a substantially enhanced catalytic activity towards HER,which is close to that of commercial Pt/C.In addition,a much superior stability compared to other three catalysts including commercial Pt/C was exhibited.Such enhancement in activity and stability can be attributed to the synergistic effect between PdAu alloy and graphene as well as the un:ique 2D nanostructures.(3)We have developed a facile method to in situ synthesize ultrathin PtNi NWs with a tunable diameter and composition on the surface of MXenes nanosheets.The PtxNi@Ti3C2 exhibited the excellent catalytic performance toward HER in both acidic and alkaline solutions.In particular,the Pt3.2,Ni@ Ti3C2 demonstrated a record low overpotential and small Tafel slope in acidic solution.Theory calculations and XPS analyses show that the coupling between the Ti3C2 nanosheets and NWs through the electron transfer optimized the Gibbs free energy for hydrogen adsorption and was responsible for such enormous enhancement in HER activities in acidic media.In addition,the vacancies on the surface of the Ti3C2 nanosheets resulting from the removal of F containing groups in alkaline media provided active sites for water dissociation,leading to the signifcant enhancement in HER activities.(4)We have developed a facile method to synthesize PtPb intermetallic nanowire on the MXenes nanosheets by a diffusion method.The in situ synthesized Pt nanowires are used as template and Pb atom were directly diffused into the Pt nanowires.The composites are employed as the catalyst for ORR and MOR and show a superior performance relative to commercial Pt/C due to the interaction between nanowire and MXenes as well as the excellent instrinsic properties of intermetallic compound.