石墨烯負載鎳基復(fù)合材料氧還原催化劑的研究
發(fā)布時間：2018-12-20 07:10
【摘要】：由于環(huán)境污染和能源緊張的加劇,科學(xué)家正努力研究新型的清潔能源來減少對傳統(tǒng)化石燃料的消耗。燃料電池,由于其高的電流密度,低的操作環(huán)境要求以及污染物排放量而廣泛被人們關(guān)注,但是,高成本的鉑基催化劑阻礙了燃料電池的大規(guī)模推廣,另外,在催化過程中產(chǎn)生的CO容易引起金屬鉑中毒,從而失去催化活性。因此,為了降低燃料電池催化劑的成本并促進其商業(yè)化應(yīng)用,對非貴金屬催化劑的研究一直都是人們關(guān)注的重點,例如,以多組分合金以及以石墨烯為載體的金屬催化劑。鑒于氧還石墨烯在各領(lǐng)域表現(xiàn)出的優(yōu)異的性能,本文以其為載體材料,與過渡金屬化合物相復(fù)合來制備復(fù)合材料催化劑,旨在探索制備高活性高穩(wěn)定性的氧還原催化劑。在本文中,將Ni O作為研究對象,GO負載的Ni(OH)_2為前驅(qū)體制備不同形貌的復(fù)合材料催化劑,所制備催化劑的結(jié)構(gòu)和形貌主要由X-射線衍射儀(XRD),Raman光譜,掃描電鏡(SEM)以及透射電鏡(TEM)測試與表征,其電化學(xué)性能主要由循環(huán)伏安法(CV)、線性掃描伏安法(LSV)、塔菲爾曲線(Tafel)以及電流-時間曲線(i-t)表示,而氧還原過程的催化機理可由旋轉(zhuǎn)圓盤電極(RDE)、交流阻抗譜圖(EIS)和旋轉(zhuǎn)環(huán)盤電極(RRDE)測試來說明。具體內(nèi)容概括為以下幾個部分:(1)首先,本文研究了在不同氣體氛圍下(空氣、氬氣和氨氣)熱解Ni(OH)_2/GO得到的s-NiO/rGO、g-NiO/rGO和g-NiO/N-rGO三種催化劑結(jié)構(gòu)形貌以及電化學(xué)性能的差異,結(jié)果表明,在空氣下熱解Ni(OH)_2/GO得到了片狀的NiO負載在rGO上,而在氬氣和氨氣氣氛下則得到了球形的NiO,并且在氨氣氣氛處理下有一部分的N原子摻雜到還原的氧化石墨烯上。電化學(xué)測試表明,g-NiO/N-rGO的電流密度和初始電壓(-0.13 V)都接近于商業(yè)Pt/C(20%)電極,而NiO/rGO催化活性提高的原因主要是在氨氣氛圍下熱解而引入了氮原子的原因,形貌對氧還原催化過程影響較小一些,RDE和RRDE測試都證明了g-NiO/N-rGO主要發(fā)生四電子反應(yīng)。(2)其次,為獲得催化活性更高的催化劑,使用金屬Pd對NiO/rGO進行修飾,主要方法是使用NaBH_4進行還原,將Pd還原到NiO/rGO上。研究表明,NiO和Pd顆粒均勻的負載在石墨烯上,金屬Pd的顆粒較大一些,主要是NaBH_4的還原性太強所導(dǎo)致的。通過電化學(xué)測試可得知,Pd修飾NiO/rGO后,無論是在起始電壓還是電流密度方面都有一定的提高,主要是Pd負載在還原氧化石墨烯上后提高了其導(dǎo)電性并減小了電極與溶液的接觸電阻,提高了其氧還原催化活性。而旋轉(zhuǎn)圓盤法和旋轉(zhuǎn)環(huán)盤法則從兩方面證明在催化氧化過程Pd@NiO/rGO主要發(fā)生四電子反應(yīng),并伴隨少量二電子反應(yīng)發(fā)生。
[Abstract]:As environmental pollution and energy tensions intensify, scientists are working on new clean energy sources to reduce the consumption of traditional fossil fuels. Fuel cells, due to their high current density, low operating environment requirements and pollutant emissions, have attracted widespread attention. However, the high cost of platinum-based catalysts has hindered the large-scale promotion of fuel cells. CO produced in the catalytic process is prone to lead to platinum poisoning, thus losing the catalytic activity. Therefore, in order to reduce the cost of fuel cell catalysts and promote their commercial application, the research of non-noble metal catalysts has been the focus of attention, such as multi-component alloys and graphene supported metal catalysts. In view of the excellent performance of Oxygenene in various fields, the composite catalyst was prepared by using it as the support material and the transition metal compound phase. The aim of this paper was to explore the preparation of oxygen reduction catalyst with high activity and stability. In this paper, Ni O was used as the research object and Ni (OH) _ 2 supported on GO was used as precursor to prepare composite catalysts with different morphologies. The structure and morphology of the catalysts were mainly determined by (XRD), Raman spectra of X-ray diffractometer. The electrochemical properties of SEM (SEM) and TEM (TEM) were characterized by cyclic voltammetry (CV), linear scanning voltammetry (CV), (LSV), Tafel curve (Tafel) and current-time curve (i-t). The catalytic mechanism of oxygen reduction can be explained by (RDE), impedance spectroscopy (EIS) and (RRDE) measurement. The specific contents are summarized as follows: (1) at first, we study the s-Nio / rGO. obtained by pyrolysis of Ni (OH) _ 2/GO in different atmosphere (air, argon and ammonia). The structural morphology and electrochemical properties of the three catalysts g-NiO/rGO and g-NiO/N-rGO were different. The results showed that the NiO supported on rGO was obtained by pyrolysis of Ni (OH) _ 2/GO in air. The spherical NiO, was obtained in argon and ammonia atmosphere, and some N atoms were doped into the reduced graphene oxide in ammonia atmosphere. Electrochemical measurements show that the current density and initial voltage (-0.13 V) of g-NiO/N-rGO are close to those of commercial Pt/C (20%) electrodes. The main reason for the increase of catalytic activity of NiO/rGO is the introduction of nitrogen atoms in the pyrolysis of ammonia atmosphere, and the morphology has less influence on the catalytic process of oxygen reduction. RDE and RRDE tests show that g-NiO/N-rGO mainly occurs four-electron reaction. (2) secondly, in order to obtain the catalyst with higher catalytic activity, the metal Pd is used to modify the NiO/rGO. The main method is to reduce NiO/rGO by using NaBH_4. Restore Pd to NiO/rGO. The results show that the particles of NiO and Pd are uniformly loaded on graphene, and the particles of metal Pd are larger, which is mainly caused by the too strong reduction of NaBH_4. The electrochemical measurements show that the initial voltage and current density of NiO/rGO modified by Pd can be improved to a certain extent. The main reason is that the Pd supported on the reduced graphene can improve the electrical conductivity, decrease the contact resistance between the electrode and the solution, and improve the catalytic activity of oxygen reduction. The rotating disk method and the rotating ring disk rule show that Pd@NiO/rGO mainly occurs in the catalytic oxidation process with a small number of two-electron reactions.
【學(xué)位授予單位】：濟南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O643.36;TB333
本文編號：2387629
[Abstract]:As environmental pollution and energy tensions intensify, scientists are working on new clean energy sources to reduce the consumption of traditional fossil fuels. Fuel cells, due to their high current density, low operating environment requirements and pollutant emissions, have attracted widespread attention. However, the high cost of platinum-based catalysts has hindered the large-scale promotion of fuel cells. CO produced in the catalytic process is prone to lead to platinum poisoning, thus losing the catalytic activity. Therefore, in order to reduce the cost of fuel cell catalysts and promote their commercial application, the research of non-noble metal catalysts has been the focus of attention, such as multi-component alloys and graphene supported metal catalysts. In view of the excellent performance of Oxygenene in various fields, the composite catalyst was prepared by using it as the support material and the transition metal compound phase. The aim of this paper was to explore the preparation of oxygen reduction catalyst with high activity and stability. In this paper, Ni O was used as the research object and Ni (OH) _ 2 supported on GO was used as precursor to prepare composite catalysts with different morphologies. The structure and morphology of the catalysts were mainly determined by (XRD), Raman spectra of X-ray diffractometer. The electrochemical properties of SEM (SEM) and TEM (TEM) were characterized by cyclic voltammetry (CV), linear scanning voltammetry (CV), (LSV), Tafel curve (Tafel) and current-time curve (i-t). The catalytic mechanism of oxygen reduction can be explained by (RDE), impedance spectroscopy (EIS) and (RRDE) measurement. The specific contents are summarized as follows: (1) at first, we study the s-Nio / rGO. obtained by pyrolysis of Ni (OH) _ 2/GO in different atmosphere (air, argon and ammonia). The structural morphology and electrochemical properties of the three catalysts g-NiO/rGO and g-NiO/N-rGO were different. The results showed that the NiO supported on rGO was obtained by pyrolysis of Ni (OH) _ 2/GO in air. The spherical NiO, was obtained in argon and ammonia atmosphere, and some N atoms were doped into the reduced graphene oxide in ammonia atmosphere. Electrochemical measurements show that the current density and initial voltage (-0.13 V) of g-NiO/N-rGO are close to those of commercial Pt/C (20%) electrodes. The main reason for the increase of catalytic activity of NiO/rGO is the introduction of nitrogen atoms in the pyrolysis of ammonia atmosphere, and the morphology has less influence on the catalytic process of oxygen reduction. RDE and RRDE tests show that g-NiO/N-rGO mainly occurs four-electron reaction. (2) secondly, in order to obtain the catalyst with higher catalytic activity, the metal Pd is used to modify the NiO/rGO. The main method is to reduce NiO/rGO by using NaBH_4. Restore Pd to NiO/rGO. The results show that the particles of NiO and Pd are uniformly loaded on graphene, and the particles of metal Pd are larger, which is mainly caused by the too strong reduction of NaBH_4. The electrochemical measurements show that the initial voltage and current density of NiO/rGO modified by Pd can be improved to a certain extent. The main reason is that the Pd supported on the reduced graphene can improve the electrical conductivity, decrease the contact resistance between the electrode and the solution, and improve the catalytic activity of oxygen reduction. The rotating disk method and the rotating ring disk rule show that Pd@NiO/rGO mainly occurs in the catalytic oxidation process with a small number of two-electron reactions.
【學(xué)位授予單位】：濟南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O643.36;TB333
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