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Electrochemical Process and Electrocatalytic Properties of Hydrogen Storage Alloy for Replacing Pt as the Anode Catalytic Material in PEMFC and AFC

Author: ChenZuo
Tutor: WangQiDong；ChenChangPin；Cesar Sequeira
School: Zhejiang University
Course: Materials Science
Keywords: Hydrogen storage alloy Fuel cell Anode Electrocatalytic Properties Electrochemical properties Surface treatment Ball milling
CLC: TM911
Type: PhD thesis
Year: 2002
Downloads: 427
Quote: 0
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Abstract

Fuel cells are following the water, fire, and soon after the rapid development of nuclear power generation technology, with large energy density, high efficiency, low pollution and low noise and other unique advantages, application or intended scope of application related to national security and people's daily lives all aspects of the national economy and is likely to have a significant impact on the industrial structure of the new energy conversion technologies. Paper summarizes the domestic fuel cell system, especially low temperature proton exchange membrane fuel cell (PEMFC) and alkaline fuel cell (AFC) in the course of development, research status and currently the main problems, and briefly summarized so far rare earth reserves hydrogen electrode alloy main research progress. On this basis, the paper identified with hydrogen storage alloy MlNi _3.65 Co _0.85 Al _0.3 Mn _0.3 as the main object of study, from the optimization of the fuel cell anode structure, improve the hydrogen storage alloy surface electro-catalytic activity and extend the working life of departure, the use of structure and material characterization and electrochemical analysis and testing and other means to explore and study the generation of hydrogen storage alloy and Pt as PEMFC AFC anode catalytic materials intrinsic characteristics, factors and prospects. First, from the thesis work of PEMFC based technology start affecting the core PEMFC membrane electrode (MEA) of the three main performance factors were studied systematically and Pt / C MEA prepared a comprehensive optimization techniques for the introduction of hydrogen storage alloy lay foundation. Found that the electrode catalyst layer is a proton exchange membrane (PEM) Nafion solution impregnated side of the MEA can be extended reaction zone D, the farther away from the PEM catalyst surface can also participate in the electrode reaction; impregnated with hot-pressed electrode and PEM facilitate proton transfer; then control the thickness of the electrode can significantly improve the exchange current density of the MEA. Integrated optimization results show that the preparation of the consolidated optimized Pt / C MEA 0.5V discharge current density of 483 mA · cm ^{-2 . Detailed study of the hydrogen storage alloy Mli _3.65 Co _0.85 Al _0.3 Mn _0.3 Pt as PEMFC MEA on behalf of the anode electrocatalytic electrochemical properties of the material. The results showed that the alloy milling, surface treatment and surface modification such as Pd plating and alloy anode load, pore size and add agents to optimize the MEA can effectively improve the hydrogen storage alloy anode electro-catalytic properties. Experimental material in hydrogen charging milled alloy has the largest surface area and the best response than electro-catalytic activity, the discharge current density and the maximum output power density than mechanical crushing alloy 1 times higher. Milled material mixed with acetylene black and the three phase boundary can expand the electrode reaction, thereby improving the hydrogen storage alloy anode catalyst layer, the electron conductivity. Surface heat alkali reduction at Zhejiang University PhD thesis rationale to further improve the hydrogen storage alloy electro-catalytic activity and specific surface area. The surface modification treatment can destroy hydrogen storage alloy surface oxide layer, but due to some Mn, AI and its oxides dissolve corrosion, some alloy surface oxides are reduced and partially hydrogenated alloy cracks are formed when fresh improve or enhance electrochemical hydrogen storage alloy anode MEA performance factor. Study found that treatment with hot alkali reduction and plating 3 t% Pd hydrogen storage alloy prepared by electrochemical MEA showed the best performance. Pd plating surface after the dissociation of the hydrogen adsorption capacity, electrical conductivity capacity significantly increased, especially in the ohmic polarization and concentration polarization phase of the discharge performance is further improved. The integrated optimization of hydrogen storage alloy anode MEA 0.5 V, the discharge current density reached 168 a · Cm-\\ 0.2 V, the discharge current of up to 232.4 a. cm \m-into constant discharge 24 hrs after the MEA output power is still 22 stone 8 mw · cm-\\ remained at the initial output power (31.31 mw · cm 'spoon 72.40 (cast alloy anode MEA i make 8 hrs the output power from the initial value 10.55 mw ·. m \working temperature and pressure effects on the electrochemical reaction studies have shown that increasing the pressure could promote the electrochemical reaction; while there exists an optimum temperature range of the experimental alloys, 60 ℃ best when electro-catalytic properties, too low then the electrode reaction is slow, too high alloy can form a relatively stable phase catalytic hydrogen. modification of different hydrogen storage alloy MINi.. SC.. 8. AI.} Mn03 three-electrode system and in alkaline AFC catalytic materials as anode electrochemical properties were studied systematically results showed that the hydrogen storage alloy by ball milling, surface treatment and surface modification such as Pd plating electro-catalytic activity were significantly improved due to the treated alloy is formed on the surface Ni-rich layer and the Pd layer and the grain refinement and surface area increases, the alloy electrode surface charge transfer impedance is reduced, the exchange current density of 90.8 InA from a cast including 'increased to 175.7hall, cast by the apparent activation braise states 19.12 kJ · mol \The decrease in the hydrogen storage alloy anode AFC structure and composition of the system, the study found that the catalyst layer of acetylene black added 2 t% * ~ 22 t% PTFE and 5 t% (NH only C. O., AFC, hydrogen storage alloy anode overpotential with minimum and optimum discharge performance optimized AFC hydrogen storage alloy anode to 50 IlbA · cm-'AFC discharge current density of the electrode potential is 0866 V; potential of 0.5 V when the discharge current densities up to 196.2 InA ·. m \is 40 ℃, the hydrogen storage alloy anode performance especially at high current densities the best performance in the AFC hydrogen storage alloy anode for different current densities in job stability study found that with the increase of the current density electrode The decline accelerated at 30 ℃ and 25 InA · cm \Discharge}

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