碳载四氧化三钴电催化材料的制备及碱金属掺杂对其性能的调控
发布时间：2018-11-28 07:34
【摘要】：针对贵金属催化剂成本高,稳定性差等问题,本论文主要制备了Co3O4/C电催化材料,对其氧还原和氧析出催化性能进行了研究,并通过碱金属(Li、Na、K)掺杂的方式提高了 Co3O4/C的电催化性能。首先用酸化的Vulcan XC-72碳黑为碳载体,并利用油浴-水热的方法,通过水热时间的调控制备出了具有不同粒径的Co3O4/C催化剂(预负载量均为50%),随着水热时间的增长,Co3O4的粒径逐渐增加,而3h时的Co3O4/C催化剂氧还原和氧析出性能都是最优的,平均粒径为4.5nm。在此基础上通过同样的方法在制备Co3O4/C的过程中进行了锂掺杂,制备出了不同锂掺杂量的碳载锂掺杂四氧化三钴催化剂(Li-Co3O4/C),氧化物的平均粒径都在4.5nm左右。而Li的掺入可以显著提高Co3O4/C的氧还原性能,随着Li掺杂量的增加,催化剂的氧还原活性呈现出先增加后减小的趋势,在Li/Co=5%时的氧还原活性是最优的,半波电位为0.865V(vs RHE),比未掺杂的提高了 21mV。而这种催化活性的增强来源于氧化物与碳载体的界面内共价键O-C=O-CoⅢ含量的增加,而这种界面共价键的增加是Li的掺杂引起的。通过上述过程,发现催化剂中氧化物与碳载体的界面相互作用对氧还原性能起着促进作用,所以本论文接下来用高石墨化碳黑为碳载体,和油浴-煅烧的方法,通过锻烧温度的调控,制备出了具有不同界面相互作用的Co304/GCB催化剂。并在这些Co3O4/GCB催化剂中发现了Co3O4的(111)晶面上形成了择优取向,且煅烧温度为300℃时的择优取向最强,且这种择优取向正是来源于氧化物与碳载体之间的界面共价键C-O-Co的作用。且Co304/GCB催化剂的氧还原活性随着择优取向的增加而增加,择优取向最强的Co3O4/GCB催化剂的氧还原活性最优,半波电位为0.83V(vsRHE)。择优取向通过减小Co304/GCB催化剂的电子带隙Eg,从而提高其氧还原活性。接下来为了研究其它碱金属掺杂对Co304/C的催化活性的而影响,采用酸化的VulcanXC-72碳黑为碳载体和油浴-水热的方法分别制备了不同掺杂量的Na-Co304/C和K-Co3O4/C催化剂。通过氧还原性能的测试,发现Na和K的掺入均能提高催化剂的氧还原性能,且分别在Na/Co=10%和K/Co=10%时的催化剂活性最高,半波电位分别为0.860V(vs RHE)和0.862V(vsRHE),比未掺杂的提高了十几毫伏。Na和K的掺杂可以提高Co304晶体内氧空位的含量,从而提高C03O4/C的催化性能。然后通过氧析出性能的测试,发现Li、Na、K的掺杂均能提高Co3O4/C的氧析出性能,与Ru02的差距进一步减小,这主要是来源于碱金属离子的掺入可以改变Co304内的阳离子分布,提高氧析出活性位点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，
本文编号：2362233
[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，
本文编号：2362233
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