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Evaluation of reduced-graphene-oxide-supported gold nanoparticles as catalytic system for electroreduction of oxygen in alkaline electrolyte

机译:氧化石墨烯负载的金纳米颗粒作为碱性电解液中氧的电还原催化体系的评价

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摘要

Chemically-reduced graphene-oxide-supported gold nanoparticles with a diameter, of 40-60 nm are considered here as catalytic materials for the reduction of oxygen in alkaline medium in comparison to analogous systems based on conventional Vulcan carbon carriers. Gold nanoparticles are prepared by the chemical reduction method, in which the NaBH4-prereduced Keggin-type phosphomolybdate heteropolyblue acts as the reducing agent for the precursor (HAuCl4). Polyoxometallate (PMo12O403) capping ligands stabilize gold nanoparticle deposits, facilitate their dispersion and attachment to carbon supports. Indeed, it is apparent from the independent diagnostic voltammetric experiments (in 0.5 mol dm (H2SO4)-H-3) that heteropolymolybdates form readily stable adsorbates on nanostructures of both gold and carbon (reduced graphene oxide and Vulcan). It is reasonable to expect that the polyoxometallate-assisted nucleation of gold has occurred in the proximity of oxygenated defects existing on carbon substrates. Under conditions of electrochemical diagnostic experiments (performed in 0.1 mol dm (3) KOH): (i) the phosphomolybdate adsorbates are removed from the interface as they undergo dissolution in alkaline medium; and (ii) the Au nanoparticles (Au loading, 30 mu g cm (2)) remain well-dispersed on the carbon as evident from transmission electron microscopy. High electrocatalytic activity of the reduced-graphene oxide-supported Au nanoparticles toward reduction of oxygen in alkaline medium is demonstrated using cyclic and rotating ring-disk voltammetric experiments. The latter system could also act as the active support for Pt nanoparticles during the reduction of oxygen. Among important issues are possible activating interactions between gold and the support, as well as presence of structural defects existing on poorly organized graphitic structure of reduced graphene oxide (as evident from Raman spectroscopy).
机译:与基于常规Vulcan碳载体的类似体系相比,直径为40-60nm的化学还原的氧化石墨烯负载的金纳米颗粒在这里被认为是用于还原碱性介质中的氧气的催化材料。金纳米颗粒通过化学还原方法制备,其中NaBH4还原的Keggin型磷钼酸杂多蓝充当前体(HAuCl4)的还原剂。多金属氧酸盐(PMo12O403)封端配体可稳定金纳米颗粒沉积物,促进其分散并附着在碳载体上。实际上,从独立的诊断伏安法实验(0.5 mol dm(H2SO4)-H-3)中可以明显看出,杂多钼酸盐易于在金和碳(还原的氧化石墨烯和Vulcan)的纳米结构上形成稳定的吸附物。可以合理地预期,多金属氧酸盐辅助的金成核发生在碳基材上存在的氧化缺陷附近。在电化学诊断实验的条件下(在0.1 mol dm(3)KOH中进行):(i)当钼钼酸盐在碱性介质中溶解时,将其从界面上除去; (ii)从透射电子显微镜可以看出,Au纳米颗粒(Au含量为30μg cm(2))保持良好地分散在碳上。使用循环和旋转环盘伏安法实验证明了氧化石墨烯负载的Au纳米粒子对碱性介质中氧的还原具有很高的电催化活性。后者的系统还可以在氧气还原过程中充当Pt纳米颗粒的活性载体。在重要的问题中,可能是金与载体之间的活化相互作用,以及还原性氧化石墨烯的组织不良的石墨结构上存在的结构缺陷的存在(从拉曼光谱学中可以明显看出)。

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