Abstract

Efficient two-step electrosynthesis of xCoO–yCo(OH)₂ (CoO_xH_y)-supported silver nanoparticles (AgNPs) is carried out in N,N-dimethylformamide (DMF) using atmospheric oxygen as a reagent and mediator at the potentials of its reduction to the superoxide ion. In the first step, the reduction of oxygen in the presence of Co (II) ions added to the solution as a salt or generated upon dissolution of a Co anode by means of electrolysis results in a mixture of amorphous cobalt oxide CoO and its hydrated form Co (OH)₂. The addition of Ag⁺ ions to the resulting solution of CoO_xH_y by similar methods results in two parallel reactions of Ag⁺ reduction to give AgNPs: reversible reduction by CoO and irreversible reduction by DMF. In the second step, oxygen-mediated electroreduction of CoO⁺ and residual quantities of Ag⁺ occurs, as well as regeneration of CoO_xH_y. The resulting spherical AgNPs are bound and stabilized by the CoO_xH_y matrix. Both steps occur quantitatively and consume the theoretical amount of electricity (2 F with respect to Co²⁺ in the first step and 1 F with respect to Ag⁺ in the second step). Depending on the production method, the size of the AgNPs varies in a range from 7±2 to 27±10 nm. The Ag/CoO_xH_y nanocomposites obtained exhibit catalytic activity in the p-nitrophenol reduction with sodium borohydride in an aqueous medium. Their activity caused by AgNPs significantly increases in the presence of cetyltrimethylammonium chloride (CTAC), a micelle-forming cationic surfactant.

中文翻译：

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xCoO–yCo（OH）2负载的银纳米颗粒的两步一锅电合成及催化活性

摘要

在N，N-二甲基甲酰胺（DMF）中，使用大气氧气作为试剂和介体，以xCoO–yCo（OH）₂（CoO _x H _y）为载体的银纳米颗粒（AgNPs）进行有效的两步电合成它还原成超氧离子。在第一步中，在以盐形式添加到溶液中或在电解溶解Co阳极时产生的Co（II）离子的存在下，氧气的还原反应会生成无定形氧化钴CoO及其水合形式的混合物Co（OH）₂。向所得的CoO _x H _y溶液中添加Ag ⁺离子通过类似的方法，会导致Ag ⁺还原反应生成AgNPs的两个平行反应：CoO可逆还原和DMF不可逆还原。在第二步中，发生氧气介导的CoO ^+的电还原和剩余量的Ag ⁺以及CoO _x H _y的再生。生成的球形AgNP被CoO _x H _y矩阵束缚并稳定。这两个步骤都定量发生，并且消耗理论电量（第一步中相对于Co ²⁺为2 F，相对于Ag ⁺为1 F在第二步）。取决于生产方法，AgNP的尺寸在7±2至27±10nm的范围内变化。所获得的Ag / CoO _x H _y纳米复合材料在水性介质中用硼氢化钠还原对硝基苯酚具有催化活性。在十六烷基三甲基氯化铵（CTAC）（一种形成胶束的阳离子表面活性剂）的存在下，由AgNP引起的它们的活性显着增加。