氧还原和氧析出是燃料电池、金属空气电池中关键的电化学反应。为了促进氧还原和氧析出反应的动力学过程,剥离制备了表面具有负电荷的氧化石墨纳米片和表面带有正电荷的钴镍纳米片层,基于静电作用通过层层自组装的方法,制备了结构有序的氧化石墨烯负载的钴镍双羟基氢氧化物纳米片层材料,并进一步通过煅烧得到了同样结构有序的具有尖晶石结构的钴镍过渡金属氧化物。通过SEM、EDS和XRD表征了所制备材料的微观结构和组成,通过电化学测试研究了所制备材料对于氧还原和氧析出反应的催化性能。结果表明,自组装制备的氧化石墨烯负载的钴镍双羟基氢氧化物纳米片具有良好的氧还原催化活性,极限电流密度和商品化的碳载铂相当,远远超过了传统的水热法合成的钴镍双羟基氢氧化物。这种催化活性的提高主要来源于自组装方法制备的材料在结构上的高度有序,钴镍双羟基氢氧化物层状结构的优势以及石墨烯的载体效应。同时,由其转变得到的具有尖晶石结构的钴镍氧化物对氧析出反应表现出较好的催化性能。
Oxygen reduction and oxygen evolution are the key electrochemical reactions in fuel cells and metal-air batteries.In order to promote the kinetic process of oxygen reduction and oxygen evolution reaction,graphite oxide(GO) nanosheets with a negative charge on the surface and cobalt-nickel nanosheets with a positive charge on the surface were exfoliate for preparing GO-supported cobalt-nickel(CoNi) layered double hydroxide nanosheet with ordered structure.Specially,the GO-supported CoNi layered double hydroxide nanosheet can transform to CoNi transition metal oxide with spinel structure at a certain condition by calcination.The microstructure and composition of the prepared materials was studied by SEM combined with EDS and XRD characterization.The catalytical performance of the prepared materials for oxygen reduction and oxygen evolution reaction was studied by electrochemical tests.The results shown that the GO-supported CoNi dihydroxy hydroxide nanosheets prepared by self-assembly had good oxygen reduction catalytic activity,and the limiting current density was comparable to the commercial carbon-supported platinum,which was far more than the corresponding material synthesized via traditional hydrothermal method.This improvement in catalytic activity was mainly due to the highly ordered structure of the materials prepared by the self-assembly method,the advantages of the layered structure of CoNi dihydroxy hydroxide,and the advantage of the GO supporter.At the same time,the CoNi oxide with spinel structure obtained from the transformation showed good catalytic performance for the oxygen evolution reaction.
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