【摘要】：針對貴金屬催化劑成本高,穩(wěn)定性差等問題,本論文主要制備了Co3O4/C電催化材料,對其氧還原和氧析出催化性能進行了研究,并通過堿金屬(Li、Na、K)摻雜的方式提高了 Co3O4/C的電催化性能。首先用酸化的Vulcan XC-72碳黑為碳載體,并利用油浴-水熱的方法,通過水熱時間的調(diào)控制備出了具有不同粒徑的Co3O4/C催化劑(預(yù)負載量均為50%),隨著水熱時間的增長,Co3O4的粒徑逐漸增加,而3h時的Co3O4/C催化劑氧還原和氧析出性能都是最優(yōu)的,平均粒徑為4.5nm。在此基礎(chǔ)上通過同樣的方法在制備Co3O4/C的過程中進行了鋰摻雜,制備出了不同鋰摻雜量的碳載鋰摻雜四氧化三鈷催化劑(Li-Co3O4/C),氧化物的平均粒徑都在4.5nm左右。而Li的摻入可以顯著提高Co3O4/C的氧還原性能,隨著Li摻雜量的增加,催化劑的氧還原活性呈現(xiàn)出先增加后減小的趨勢,在Li/Co=5%時的氧還原活性是最優(yōu)的,半波電位為0.865V(vs RHE),比未摻雜的提高了 21mV。而這種催化活性的增強來源于氧化物與碳載體的界面內(nèi)共價鍵O-C=O-CoⅢ含量的增加,而這種界面共價鍵的增加是Li的摻雜引起的。通過上述過程,發(fā)現(xiàn)催化劑中氧化物與碳載體的界面相互作用對氧還原性能起著促進作用,所以本論文接下來用高石墨化碳黑為碳載體,和油浴-煅燒的方法,通過鍛燒溫度的調(diào)控,制備出了具有不同界面相互作用的Co304/GCB催化劑。并在這些Co3O4/GCB催化劑中發(fā)現(xiàn)了Co3O4的(111)晶面上形成了擇優(yōu)取向,且煅燒溫度為300℃時的擇優(yōu)取向最強,且這種擇優(yōu)取向正是來源于氧化物與碳載體之間的界面共價鍵C-O-Co的作用。且Co304/GCB催化劑的氧還原活性隨著擇優(yōu)取向的增加而增加,擇優(yōu)取向最強的Co3O4/GCB催化劑的氧還原活性最優(yōu),半波電位為0.83V(vsRHE)。擇優(yōu)取向通過減小Co304/GCB催化劑的電子帶隙Eg,從而提高其氧還原活性。接下來為了研究其它堿金屬摻雜對Co304/C的催化活性的而影響,采用酸化的VulcanXC-72碳黑為碳載體和油浴-水熱的方法分別制備了不同摻雜量的Na-Co304/C和K-Co3O4/C催化劑。通過氧還原性能的測試,發(fā)現(xiàn)Na和K的摻入均能提高催化劑的氧還原性能,且分別在Na/Co=10%和K/Co=10%時的催化劑活性最高,半波電位分別為0.860V(vs RHE)和0.862V(vsRHE),比未摻雜的提高了十幾毫伏。Na和K的摻雜可以提高Co304晶體內(nèi)氧空位的含量,從而提高C03O4/C的催化性能。然后通過氧析出性能的測試,發(fā)現(xiàn)Li、Na、K的摻雜均能提高Co3O4/C的氧析出性能,與Ru02的差距進一步減小,這主要是來源于堿金屬離子的摻入可以改變Co304內(nèi)的陽離子分布,提高氧析出活性位點Co3+的含量。
[Abstract]:In order to solve the problems of high cost and poor stability of noble metal catalysts, Co3O4/C electrocatalytic materials were prepared in this paper. The catalytic properties of oxygen reduction and oxygen precipitation were studied, and the catalytic properties of Li,Na, were studied. K) doping improved the electrocatalytic performance of Co3O4/C. Firstly, using acidified Vulcan XC-72 carbon black as carbon carrier and oil bath hydrothermal method, the Co3O4/C catalysts with different particle sizes (50% preloading) were prepared by controlling the hydrothermal time, and with the increase of hydrothermal time. The particle size of Co3O4 increased gradually, and the oxygen reduction and oxygen precipitation properties of Co3O4/C catalyst were optimized at 3 h, with an average particle size of 4.5 nm. On this basis, lithium doping was carried out in the process of preparation of Co3O4/C by the same method, and different lithium doped carbon-doped cobalt trioxide (Li-Co3O4/C) catalysts were prepared. The average particle size of the oxides was about 4.5nm. The oxygen reduction activity of the catalyst increased first and then decreased with the increase of the amount of Li doping, and the oxygen reduction activity of the catalyst was the best at Li/Co= 5, and the oxygen reduction activity of the catalyst increased significantly with the addition of Li, and the oxygen reduction activity of the catalyst increased firstly and then decreased with the increase of the amount of Li doping. The half-wave potential of 0.865 V (vs RHE), is 21 MV higher than that of undoped. The enhancement of the catalytic activity is due to the increase of O-C=O-Co 鈪，

本文編號：2362233