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New Progress Has Been Made In The Research Of One-dimensional High-efficiency Nanocatalysts For Methanol Oxidation
Jan 09, 2018

Recently, Prof. Yu Shuhong from National Key Laboratory of Microscale Physical Chemistry at Hefei University of Science and Technology, made a successful preparation of one-dimensional ultrafine quaternary PtPdRuTe nanotubes and one-dimensional open-pore PtCu nanotube catalysts. This type The catalyst has a stable and efficient methanol oxidation performance. Related results are respectively found in "Synthesis of Low Pt-Based Quaternary Pt PdTeu Nanotubes with Optimized Incorporation of Pd for Enhanced Electrocatalytic Activity" and "Highly crystalline PtCu nanotubes with three dimensional molecular accessible restructured surface for efficient catalysis", respectively, in J. Am. Chem. Soc. And Energy Environ. Sci.


Methanol fuel cell is a proton exchange membrane fuel cell with methanol as the liquid fuel, which not only has the advantages of rich fuel source, low cost, convenient storage and transportation safety, but also has high attention to methanol with high energy density. However, the development of methanol fuel cells needs to increase the platinum loading due to the slow reaction kinetics of the methanolysis of the anode and the susceptibility of the metal platinum catalyst to poisoning. Thus, the number of active sites exposed to the catalyst as well as the surface structure, composition and arrangement of the atoms are crucial to improve platinum utilization and catalytic performance. At present, a large number of studies have focused on the exploration of different transition metals and platinum to form alloying or heterostructured catalysts for modification of the platinum electronic structure, thereby achieving the purpose of reducing the platinum loading and increasing the utilization of platinum. Nanostructured materials with open-cell structures such as nanocages, nanoframes, hollow spheres, etc., also minimize the cost by maximizing the use of the active metal by imparting high surface area, porosity, and active surfaces in contact with the reactants in three dimensions. In addition, another important key issue that constrains the development of fuel cells is the stability of the catalyst. At present, the performance improvement of many platinum-based catalysts in harsh electrochemical environments is still limited by the composition or structural stability of nanomaterials. During electrochemical testing, platinum tends to oxidize or dissolve, resulting in loss of active specific surface area or decrease of catalytic activity, which is related to the structure and composition of nanomaterials. In view of the fuel cell development constraints, by controlling the catalyst structure, composition, surface, bond length and other parameters to improve the physical properties and electronic structure of platinum-based nanomaterials, its intrinsic activity and stability of the retention mechanism is particularly important. The key question is how to realize the controllable and effective use of different atoms in the catalytic reaction by the simple and effective preparation method and how to design a highly efficient and stable anode catalyst with renewable catalytic properties. The practical application of methanol fuel cell has an important role in promoting.

Figure 1. HAADF / STEM and HRTEM images of (AC) Pt17Pd16Ru22Te45 nanotubes. (D) The mass activities of PtPdRuTe, PtRuTe and Pt / C catalysts were normalized to the loading masses of PtPd and Pt, respectively; CV curve before and after 1000 cycles.


To this end, the researchers used highly reactive tellurium nanowires as a template, the potential difference using the substitution reaction, the successful preparation of a controlled composition of quaternary PtPdRuTe nanotubes catalyst with a high potential potential of palladium and The formation of platinum alloy and its composition to achieve controlled, to reduce the platinum oxidation potential to enhance the stability of platinum is very important. As a quaternary catalyst, each element plays an indispensable and important role in catalysis: While tellurium nanowires act as a reducing agent and template, the unsubstituted tellurium atoms together with the other three noble metal elements support the nanotube structure framework And reduce the composition of the precious metal; Platinum atom to provide the active site dissociation of methanol to form Pt-CO, while ruthenium atoms provide dissociation water to form Ru-OH active site, promote the oxidation of CO on the active site of platinum to form CO2; (16%) has a modification effect on the electronic structure of platinum, more importantly, palladium can increase the oxidation potential of platinum to reduce the oxidation and etching of platinum atoms and enhance the composition stability of the catalyst. By regulating the composition, enhance the interaction between atoms, play a different atom in the catalytic reaction of the advantages, so as to promote the efficient catalytic reaction (Figure 1). This work was published in J. Am. Chem. Soc. (J. Am. Chem. Soc. 2017, 139, 5890-5895). Co-authors of the dissertation are Ph.D. Masters and Associate Professor Li Huili.

Figure 2. (A) HRTEM plots of PtCu nanotubes composed of highly crystalline nanoparticles. (i-iv) is a magnified HRTEM image of the area marked in boxes i, ii, iii, iv in (A); (B) STEM nanotube and high resolution STEM-EDS elemental profiles showing Pt and Cu elements (C) Correlation of mass specific activity and area specific activity of related catalysts; (D) Mass specific activity with time of regeneration.


In addition to maintaining the stability of the catalyst, the active regeneration or re-use of the catalyst is also an important issue in the face of limited and expensive platinum sources. In response to this problem, the researchers demonstrated the high activity and long-term stability of PtCu nanotubes with one-dimensional open-cell structure in methanol oxidation catalysis. The mass specific activity and area specific activity of Pt1Cu1-AA nanotubes reached 2252 mA mg-1 and 6.09 mA cm-2, respectively, which were 5.5 and 10.3 times that of the commercial Pt / C catalyst. After the stability test, the activity of the nanotube catalyst not only did not decline, but higher or maintain the initial value, through a simple cyclic voltammetry test, can achieve high activity catalyst regeneration (Figure 2). Maintaining the stability is mainly due to the reformation of the catalyst surface during the activation process. The surface copper atoms are etched and the platinum atoms are rearranged to form a core-shell structure, which increases the compressive stress and greatly improves the stability of the catalyst. Combined with the characterization results of electron microscopy, the catalyst shows better crystallinity and maintains the one-dimensional nanotube structure after the stability test, and has good structural stability. On the whole, the development of PtCu catalyst based on one-dimensional open-cell structure is expected to be extended to other platinum-based materials. The high-activity regeneration reduces the amount of platinum-based catalyst in practical fuel cell applications, and studies on the stability of the catalyst Provide a new idea. The research was published in Energy Environ. Sci. (Energy Environ. Sci. 2017, DOI: 10.1039 / C7EE00573C). The co-lead author of the paper was Associate Researcher Li Huili and PhD student Fu Qiqi.


The above research is supported by the innovative research group of NSFC, the National Natural Science Foundation of China, the Key Research Project of Frontier Science of Chinese Academy of Sciences, the National Major Scientific Research Program, Suzhou Nanotechnology Collaborative Innovation Center, the Nanoscale Scientific Center of Excellence of Chinese Academy of Sciences, Center for Excellence User Funding.