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Catalytic Activity of Transition Metal Nitrides for the Eferential Oxidation of CO in H2Rich Stream

Author: ZhangXiaoHong
Tutor: PengFeng
School: South China University of Technology
Course: Industrial Catalysis
Keywords: transition metal nitrides transition metal phosphides preferential CO oxidation(PROX) platinum fuel cell
CLC: TM911.4
Type: Master's thesis
Year: 2012
Downloads: 82
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Abstract


Proton exchange membrane fuel cell （PEMFC） is a new type a clean and efficient greenbattery, which is pollution-free and has high energy conversion when used as power. However,the H2-rich feed gas applied in the anode pole of PEMFC contains trace amount of CO thatwould poison the platinum electrode. Therefore, the trace CO must be removed. Among thevarious ways available to remove CO, preferential CO oxidation （PROX） has been regardedas the most promising method. The commercial PROX catalyst is based on the precious metalof platinum. Due to the similar catalytic properties as platinum, transition metal nitrides andphosphides have attracted much interest. In this paper, transition metal nitrides andphosphides have been first studied in the PROX reaction. Some preparation conditions suchas synthesis temperature, preparation method and metal loading were investigated. Thecatalysts were characterized by means of XRD, BET, XPS, chemisorption, etc.The γ-Al2O3supported transition metal nitrides （Co4N, Mo2N, Fe3N and W2N） wereprepared with impregnation method. The results showed the best PROX activity ofCo4N/γ-Al2O3catalyst. With synthesis temperature of700oC, the CO convertion of3wt%Co4N/γ-Al2O3at200oC and220oC were96%and100%, respectively, as well as goodstability.The supported cobalt-platinum catalysts for PROX reaction were investigated in thispaper. By investigating the conditions of synthesis temperature, the metal loading of cobaltand platinum and so on, the results suggested that20wt%Co4N/2wt%Pt/γ-Al2O3catalysthad the best activity with synthesis temperature of700oC. The CO convertion reached almost100%at80oC and had good stability. When10%H2O and15%CO2were added to the feedgas, the CO convertion maintained above90%with good stability. Through the O2and COchemisorption results, it was deduced that, low-temperature oxidation of CO onCo4N/Pt/γ-Al2O3catalyst would obey a dual-site non-competitive mechanism, where Pt actedas a CO adsorption site and Co served as an O2activation site, respectively. Hence,Co4N/Pt/γ-Al2O3catalyst exhibited a high CO-PROX activity at low temperatures and mayhas a promising prospect for application.Transition metal phosphides were studied in PROX reaction. The results showed that,unsupported Co2P catalyst had preferable activity. The CO convertion reached almost100%at200oC and had good stability. While as to γ-Al2O3supported Co2P catalyst, the COconvertion was about98%at220oC.

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CLC: > Industrial Technology > Electrotechnical > Independent power supply technology (direct power) > Chemical power sources,batteries, fuel cells > Fuel cell
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