Controllable Synthesis Of High Performance Platinum-based Core-shell Nanomaterials And Their Electrocatalytic Oxidation Of Methanol

Direct Methanol Fuel Cell(DMFC)have become a hot spot for researchers of new energy technology because of its advantages such as high energy conversion efficiency,easy filling,environmentally friendly and diversified sources.Many studies have shown that the anode catalyst is one of the“bottleneck”problems that limit the large-scale commercial application of DMFC.Therefore,synthesis low-cost,high activity and excellent stability of the anode catalyst has always been the target of researchers in the field of DMFC.It is an important strategy to increase the catalytic activity and stability by adjusting the electronic structure and morphology of the catalyst,and then increasing the catalytic active site and intrinsic activity of the catalyst.We have synthesized Au@GQDs@Pt dendrite and nanowires by Graphene Quantum Dots(GQDs)as the auxiliary,which is a unique zero-dimensional(0D) carbon nanomaterial,and without using any of the stabilizer and shape-directing agent.Then,dendrite/nanowires as seed,introduce the non-noble metal Pb/Bi,trying to adjust the morphology of nanomaterials and the electronic structure of the Pt,which can increase the numbers of exposure catalytic active site,and improve the intrinsic activity of the catalyst.1.In order to satisfy the low cost of market demand,we try to introduce the Au and Pb,there are more abundant and cheaper than Pt.By tuning the composition,structure,and morphology of the catalyst,we explored the growth mechanism of Au@GQDs.By controlling the reaction time,we synthesized Au@GQDs nanowires(NWs).Then we successfully synthesized the Au@GQDs@Pt and Au@GQDs@Pt_3.5Pb NWs by using Au@GQDs NWs as seed.Then,we tested the electrocatalytic performance of Au@GQDs@Pt_3.5Pb NWs in alkaline methanol.The results show that the Au@GQDs@Pt_3.5Pb NWs have certain MOR activity,which is better than Au@GQDs NWs and commercial Pt/C.Through transmission electron microscopy(TEM),it was found that the shells of Au@GQDs@Pt_3.5Pb NWs were composed of nanoparticles.2.Three-dimensional(3D) dendrite structure shows excellent electrocatalytic activity because of its large area,rough surface,and more atomic step and defects.Inspired by these,we successfully synthesized Au@GQDs nanoparticles according to the growth mechanism of Au@GQDs.Taking nanoparticles as seeds,we synthesized three-dimensional Au@GQDs@Pt dendrites and Au@GQDs@Pt_xPb series nano pompoms with different Pt/Pb molar ratios by a convenient and environmental method,and without adding any morphology oriented agent and stabilizer.The electrochemical results show that the optimized Au@GQDs@Pt_3.5Pb nano pompoms catalyst has best methanol oxidation reaction(MOR)activity,CO toxicity resistance and stability,which is better than that of Au@GQDs@Pt nano dendrites,GQDs@Pt_3.5Pb,and commercial Pt/C.The initial potential of Au@GQDs@Pt_3.5Pb nano-pompous catalyst(-0.54 V)was much earlier than that of commercial Pt/C catalyst(-0.44 V),and the oxidation current of Au@GQDs@Pt_3.5Pb nano-pompous catalyst was 98.86 m A/cm²,which is 37.88 times than that of commercial Pt/C(2.61 m A/cm²).As a catalyst for MOR,the performance is enhanc while the cost is reduced.The higher MOR activity was ascribed to the electronic effects between GQDs,Au,and Pt-Pb,as well as the abundant channels provided by the pompon structure.3.From the perspective of environmental protection of catalyst,we try to replace toxic metal Pb with green metal Bi.We found that the method of preparing Au@GQDs@Pt_xPb nano-pompous is also suitable for the synthesis of Au@GQDs@Pt_xBi nano-pompous,with Au@GQDs as the core and Pt Bi dendrites as the shell.Compared with Au@GQDs@Pt,Au@Pt_3.5Bi,and commercial Pt/C,it is interesting that the prepared Au@GQDs@Pt_3.5Bi still showed excellent MOR activity(114 m A/cm²),stability,and anti-CO toxicity.It can be seen that the dendritic structure is very important for providing a large active surface area and facilitating the access of methanol molecules.In addition,the high catalytic performance of Au@GQDs@Pt_3.5Bi nano-pompous can be attributed to the electronic effect and synergistic effect of Pt and Bi after alloying,which can reduce the d-band center of Pt and promote the desorption of carbon intermediates,especially the adsorbed of CO,thus effectively improving the electrocatalytic activity of Au@GQDs@Pt_3.5Bi nano-pompous.